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Sample records for co2brayton cycle control

  1. Scaling considerations for a multi-megawatt class supercritical CO2 brayton cycle and commercialization.

    SciTech Connect

    Fleming, Darryn D.; Holschuh, Thomas Vernon,; Conboy, Thomas M.; Pasch, James Jay; Wright, Steven A; Rochau, Gary E; Fuller, Robert Lynn

    2013-11-01

    Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

  2. Operation and analysis of a supercritical CO2 Brayton cycle.

    SciTech Connect

    Wright, Steven Alan; Radel, Ross F.; Vernon, Milton E.; Pickard, Paul S.; Rochau, Gary Eugene

    2010-09-01

    Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for use with solar, nuclear or fossil heat sources. The focus of this work has been on the supercritical CO{sub 2} cycle (S-CO2) which has the potential for high efficiency in the temperature range of interest for these heat sources, and is also very compact, with the potential for lower capital costs. The first step in the development of these advanced cycles was the construction of a small scale Brayton cycle loop, funded by the Laboratory Directed Research & Development program, to study the key issue of compression near the critical point of CO{sub 2}. This document outlines the design of the small scale loop, describes the major components, presents models of system performance, including losses, leakage, windage, compressor performance, and flow map predictions, and finally describes the experimental results that have been generated.

  3. Transient Load Following and Control Analysis of Advanced S-CO2 Power Conversion with Dry Air Cooling

    SciTech Connect

    Moisseytsev, Anton; Sienicki, James J.

    2016-01-01

    Supercritical carbon dioxide (S-CO2) Brayton cycles are under development as advanced energy converters for advanced nuclear reactors, especially the Sodium-Cooled Fast Reactor (SFR). The use of dry air cooling for direct heat rejection to the atmosphere ultimate heat sink is increasingly becoming a requirement in many regions due to restrictions on water use. The transient load following and control behavior of an SFR with an S-CO2 cycle power converter utilizing dry air cooling have been investigated. With extension and adjustment of the previously existing control strategy for direct water cooling, S-CO2 cycle power converters can also be used for load following operation in regions where dry air cooling is a requirement

  4. Task Order 20: Supercritical Carbon Dioxide Brayton Cycle Energy Conversion Study

    SciTech Connect

    Murray, Paul; Lindsay, Edward; McDowell, Michael; Huang, Megan

    2015-04-23

    AREVA Inc. developed this study for the US Department of Energy (DOE) office of Nuclear Energy (NE) in accordance with Task Order 20 Statement of Work (SOW) covering research and development activities for the Supercritical Carbon Dioxide (sCO2) Brayton Cycle energy conversion. The study addresses the conversion of sCO2 heat energy to electrical output by use of a Brayton Cycle system and focuses on the potential of a net efficiency increase via cycle recuperation and recompression stages. The study also addresses issues and study needed to advance development and implementation of a 10 MWe sCO2 demonstration project.

  5. Myc and cell cycle control.

    PubMed

    Bretones, Gabriel; Delgado, M Dolores; León, Javier

    2015-05-01

    Soon after the discovery of the Myc gene (c-Myc), it became clear that Myc expression levels tightly correlate to cell proliferation. The entry in cell cycle of quiescent cells upon Myc enforced expression has been described in many models. Also, the downregulation or inactivation of Myc results in the impairment of cell cycle progression. Given the frequent deregulation of Myc oncogene in human cancer it is important to dissect out the mechanisms underlying the role of Myc on cell cycle control. Several parallel mechanisms account for Myc-mediated stimulation of the cell cycle. First, most of the critical positive cell cycle regulators are encoded by genes induced by Myc. These Myc target genes include Cdks, cyclins and E2F transcription factors. Apart from its direct effects on the transcription, Myc is able to hyperactivate cyclin/Cdk complexes through the induction of Cdk activating kinase (CAK) and Cdc25 phosphatases. Moreover, Myc antagonizes the activity of cell cycle inhibitors as p21 and p27 through different mechanisms. Thus, Myc is able to block p21 transcription or to induce Skp2, a protein involved in p27 degradation. Finally, Myc induces DNA replication by binding to replication origins and by upregulating genes encoding proteins required for replication initiation. Myc also regulates genes involved in the mitotic control. A promising approach to treat tumors with deregulated Myc is the synthetic lethality based on the inhibition of Cdks. Thus, the knowledge of the Myc-dependent cell cycle regulatory mechanisms will help to discover new therapeutic approaches directed against malignancies with deregulated Myc. This article is part of a Special Issue entitled: Myc proteins in cell biology and pathology. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Structural and creep-fatigue evaluation

    DOE PAGES

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; ...

    2016-06-06

    A supercritical carbon dioxide (sCO2) Brayton cycle is an emerging high energy-density cycle undergoing extensive research due to the appealing thermo-physical properties of sCO2 and single phase operation. Development of a solar receiver capable of delivering sCO2 at 20 MPa and 700 °C is required for implementation of the high efficiency (~50%) solar powered sCO2 Brayton cycle. In this work, extensive candidate materials are review along with tube size optimization using the ASME Boiler and Pressure Vessel Code. Moreover, temperature and pressure distribution obtained from the thermal-fluid modeling (presented in a complementary publication) are used to evaluate the thermal andmore » mechanical stresses along with detailed creep-fatigue analysis of the tubes. The lifetime performance of the receiver tubes were approximated using the resulting body stresses. A cyclic loading analysis is performed by coupling the Strain-Life approach and the Larson-Miller creep model. The structural integrity of the receiver was examined and it was found that the stresses can be withstood by specific tubes, determined by a parametric geometric analysis. Furthermore, the creep-fatigue analysis displayed the damage accumulation due to cycling and the permanent deformation on the tubes showed that the tubes can operate for the full lifetime of the receiver.« less

  7. 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.

  8. Variable pressure power cycle and control system

    DOEpatents

    Goldsberry, Fred L.

    1984-11-27

    A variable pressure power cycle and control system that is adjustable to a variable heat source is disclosed. The power cycle adjusts itself to the heat source so that a minimal temperature difference is maintained between the heat source fluid and the power cycle working fluid, thereby substantially matching the thermodynamic envelope of the power cycle to the thermodynamic envelope of the heat source. Adjustments are made by sensing the inlet temperature of the heat source fluid and then setting a superheated vapor temperature and pressure to achieve a minimum temperature difference between the heat source fluid and the working fluid.

  9. Technology Assessment Report: Duty Cycling Controllers Revisited

    SciTech Connect

    Webster, Tom; Benenson, Peter

    1998-05-01

    This report covers an assessment of two brands of energy management controllers that are currently being offered that utilize the principle of duty cycling to purportedly save energy for unitary air conditioners and heat pumps, gas furnaces, and gas fired boilers. The results of an extensive review of past research on this subject as well as a review of vendor sponsored field testing of these controllers compares these newer controllers to those of the past. Included also is a discussion of how the duty cycling principle is prone to misinterpretation as to its potential to save energy.

  10. Neuromuscular Control and Coordination during Cycling

    ERIC Educational Resources Information Center

    Li, Li

    2004-01-01

    The neuromuscular control aspect of cycling has been investigated through the effects of modifying posture and cadence. These studies show that changing posture has a more profound influence on neuromuscular coordination than does changing slope. Most of the changes with standing posture occur late in the downstroke: increased ankle and knee joint…

  11. Neuromuscular Control and Coordination during Cycling

    ERIC Educational Resources Information Center

    Li, Li

    2004-01-01

    The neuromuscular control aspect of cycling has been investigated through the effects of modifying posture and cadence. These studies show that changing posture has a more profound influence on neuromuscular coordination than does changing slope. Most of the changes with standing posture occur late in the downstroke: increased ankle and knee joint…

  12. Cell cycle control across the eukaryotic kingdom.

    PubMed

    Harashima, Hirofumi; Dissmeyer, Nico; Schnittger, Arp

    2013-07-01

    Almost two billion years of evolution have generated a vast and amazing variety of eukaryotic life with approximately 8.7 million extant species. Growth and reproduction of all of these organisms depend on faithful duplication and distribution of their chromosomes to the newly forming daughter cells in a process called the cell cycle. However, most of what is known today about cell cycle control comes from a few model species that belong to the unikonts; that is, to only one of five 'supergroups' that comprise the eukaryotic kingdom. Recently, analyzing species from distantly related clades is providing insights into general principles of cell cycle regulation and shedding light on its evolution. Here, referring to animal and fungal as opposed to non-unikont systems, especially flowering plants from the archaeplastid supergroup, we compare the conservation of central cell cycle regulator functions, the structure of network topologies, and the evolutionary dynamics of substrates of core cell cycle kinases. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Supercritical CO2 Power Cycles: Design Considerations for Concentrating Solar Power

    SciTech Connect

    Neises, Ty; Turchi, Craig

    2014-09-01

    A comparison of three supercritical CO2 Brayton cycles: the simple cycle, recompression cycle and partial-cooling cycle indicates the partial-cooling cycle is favored for use in concentrating solar power (CSP) systems. Although it displays slightly lower cycle efficiency versus the recompression cycle, the partial-cooling cycle is estimated to have lower total recuperator size, as well as a lower maximum s-CO2 temperature in the high-temperature recuperator. Both of these effects reduce recuperator cost. Furthermore, the partial-cooling cycle provides a larger temperature differential across the turbine, which translates into a smaller, more cost-effective thermal energy storage system. The temperature drop across the turbine (and by extension, across a thermal storage system) for the partial-cooling cycle is estimated to be 23% to 35% larger compared to the recompression cycle of equal recuperator conductance between 5 and 15 MW/K. This reduces the size and cost of the thermal storage system. Simulations by NREL and Abengoa Solar indicate the partial-cooling cycle results in a lower LCOE compared with the recompression cycle, despite the former's slightly lower cycle efficiency. Advantages of the recompression cycle include higher thermal efficiency and potential for a smaller precooler. The overall impact favors the use of a partial-cooling cycle for CSP compared to the more commonly analyzed recompression cycle.

  14. Control points within the cell cycle

    SciTech Connect

    Van't Hof, J.

    1984-01-01

    Evidence of the temporal order of chromosomal DNA replication argues favorably for the view that the cell cycle is controlled by genes acting in sequence whose time of expression is determined by mitosis and the amount of nuclear DNA (2C vs 4C) in the cell. Gl and G2 appear to be carbohydrate dependent in that cells starved of either carbohydrate of phosphate fail to make these transitions. Cells deprived of nitrate, however, fail only at Gl to S transition indicating that the controls that operate in G1 differ from those that operate in G2. 46 references, 5 figures.

  15. Optimization and Comparison of Direct and Indirect Supercritical Carbon Dioxide Power Plant Cycles for Nuclear Applications

    SciTech Connect

    Edwin A. Harvego; Michael G. McKellar

    2011-11-01

    There have been a number of studies involving the use of gases operating in the supercritical mode for power production and process heat applications. Supercritical carbon dioxide (CO2) is particularly attractive because it is capable of achieving relatively high power conversion cycle efficiencies in the temperature range between 550 C and 750 C. Therefore, it has the potential for use with any type of high-temperature nuclear reactor concept, assuming reactor core outlet temperatures of at least 550 C. The particular power cycle investigated in this paper is a supercritical CO2 Recompression Brayton Cycle. The CO2 Recompression Brayton Cycle can be used as either a direct or indirect power conversion cycle, depending on the reactor type and reactor outlet temperature. The advantage of this cycle when compared to the helium Brayton cycle is the lower required operating temperature; 550 C versus 850 C. However, the supercritical CO2 Recompression Brayton Cycle requires an operating pressure in the range of 20 MPa, which is considerably higher than the required helium Brayton cycle operating pressure of 8 MPa. This paper presents results of analyses performed using the UniSim process analyses software to evaluate the performance of both a direct and indirect supercritical CO2 Brayton Recompression cycle for different reactor outlet temperatures. The direct supercritical CO2 cycle transferred heat directly from a 600 MWt reactor to the supercritical CO2 working fluid supplied to the turbine generator at approximately 20 MPa. The indirect supercritical CO2 cycle assumed a helium-cooled Very High Temperature Reactor (VHTR), operating at a primary system pressure of approximately 7.0 MPa, delivered heat through an intermediate heat exchanger to the secondary indirect supercritical CO2 Brayton Recompression cycle, again operating at a pressure of about 20 MPa. For both the direct and indirect cycles, sensitivity calculations were performed for reactor outlet temperature

  16. Size sensors in bacteria, cell cycle control, and size control

    PubMed Central

    Robert, Lydia

    2015-01-01

    Bacteria proliferate by repetitive cycles of cellular growth and division. The progression into the cell cycle is admitted to be under the control of cell size. However, the molecular basis of this regulation is still unclear. Here I will discuss which mechanisms could allow coupling growth and division by sensing size and transmitting this information to the division machinery. Size sensors could act at different stages of the cell cycle. During septum formation, mechanisms controlling the formation of the Z ring, such as MinCD inhibition or Nucleoid Occlusion (NO) could participate in the size-dependence of the division process. In addition or alternatively, the coupling of growth and division may occur indirectly through the control of DNA replication initiation. The relative importance of these different size-sensing mechanisms could depend on the environmental and genetic context. The recent demonstration of an incremental strategy of size control in bacteria, suggests that DnaA-dependent control of replication initiation could be the major size control mechanism limiting cell size variation. PMID:26074903

  17. Size sensors in bacteria, cell cycle control, and size control.

    PubMed

    Robert, Lydia

    2015-01-01

    Bacteria proliferate by repetitive cycles of cellular growth and division. The progression into the cell cycle is admitted to be under the control of cell size. However, the molecular basis of this regulation is still unclear. Here I will discuss which mechanisms could allow coupling growth and division by sensing size and transmitting this information to the division machinery. Size sensors could act at different stages of the cell cycle. During septum formation, mechanisms controlling the formation of the Z ring, such as MinCD inhibition or Nucleoid Occlusion (NO) could participate in the size-dependence of the division process. In addition or alternatively, the coupling of growth and division may occur indirectly through the control of DNA replication initiation. The relative importance of these different size-sensing mechanisms could depend on the environmental and genetic context. The recent demonstration of an incremental strategy of size control in bacteria, suggests that DnaA-dependent control of replication initiation could be the major size control mechanism limiting cell size variation.

  18. Controls over nitrogen cycling in California chaparral

    NASA Astrophysics Data System (ADS)

    Hanan, E. J.; Schimel, J.

    2013-12-01

    Chaparral landscapes of southern California and other Mediterranean-type ecosystems are structured by fire. They exist in environments that typically do not receive rain for 6 months or more at a time, making combustion inevitable. The heavy winter rains following fire can erode soil and leach nutrients such as nitrogen into streams and reservoirs, particularly along slopes that have been denuded. The extent to which nitrogen is cycled and redistributed following fire is a function of the rate at which soil microbes metabolize nitrogen into mobile forms such as nitrate. However, the specific mechanisms controlling nitrogen metabolism in chaparral are not fully understood. We measured mineralization and nitrification rates in ecosystems dominated by species typical of southern and central California chaparral, and conducted a laboratory incubation to experimentally examine the influence of pH, charcoal, and ammonium supply on nitrogen dynamics. Nitrate production was significantly enhanced in recently burned chaparral, which correlated with elevated soil pH. Enhanced pH can both raise the solubility of soil organic matter, and stimulate nitrification, while fires simultaneously release nitrifying bacteria from competition with vegetation for ammonium. To further explore these processes, we applied ammonium, pH, and charcoal treatments to samples from 4 chaparral stands, which burned 1, 4, 20 and 40 years ago, using a factorial design. Treated soils were incubated in mason jars at 50% water holding capacity for 8 weeks. Soil respiration, substrate induced respiration, mineralization, nitrification, and nitrification potential were measured periodically to evaluate whether ammonium addition, pH and the presence of charcoal influence substrate production and nitrification. The threat nitrate of leaching following fire grows with climate change, because fire and precipitation regimes are expected to become both increasingly variable and punctuated by more intense events

  19. Ubiquitin ligases and cell cycle control.

    PubMed

    Teixeira, Leonardo K; Reed, Steven I

    2013-01-01

    The ubiquitin-proteasome system plays a pivotal role in the sequence of events leading to cell division known as the cell cycle. Not only does ubiquitin-mediated proteolysis constitute a critical component of the core oscillator that drives the cell cycle in all eukaryotes, it is also central to the mechanisms that ensure that the integrity of the genome is maintained. These functions are primarily carried out by two families of E3 ubiquitin ligases, the Skp/cullin/F-box-containing and anaphase-promoting complex/cyclosome complexes. However, beyond those functions associated with regulation of central cell cycle events, many peripheral cell cycle-related processes rely on ubiquitylation for signaling, homeostasis, and dynamicity, involving additional types of ubiquitin ligases and regulators. We are only beginning to understand the diversity and complexity of this regulation.

  20. Cell cycle control and seed development

    PubMed Central

    Dante, Ricardo A.; Larkins, Brian A.; Sabelli, Paolo A.

    2014-01-01

    Seed development is a complex process that requires coordinated integration of many genetic, metabolic, and physiological pathways and environmental cues. Different cell cycle types, such as asymmetric cell division, acytokinetic mitosis, mitotic cell division, and endoreduplication, frequently occur in sequential yet overlapping manner during the development of the embryo and the endosperm, seed structures that are both products of double fertilization. Asymmetric cell divisions in the embryo generate polarized daughter cells with different cell fates. While nuclear and cell division cycles play a key role in determining final seed cell numbers, endoreduplication is often associated with processes such as cell enlargement and accumulation of storage metabolites that underlie cell differentiation and growth of the different seed compartments. This review focuses on recent advances in our understanding of different cell cycle mechanisms operating during seed development and their impact on the growth, development, and function of seed tissues. Particularly, the roles of core cell cycle regulators, such as cyclin-dependent-kinases and their inhibitors, the Retinoblastoma-Related/E2F pathway and the proteasome-ubiquitin system, are discussed in the contexts of different cell cycle types that characterize seed development. The contributions of nuclear and cellular proliferative cycles and endoreduplication to cereal endosperm development are also discussed. PMID:25295050

  1. Cell cycle control and seed development.

    PubMed

    Dante, Ricardo A; Larkins, Brian A; Sabelli, Paolo A

    2014-01-01

    Seed development is a complex process that requires coordinated integration of many genetic, metabolic, and physiological pathways and environmental cues. Different cell cycle types, such as asymmetric cell division, acytokinetic mitosis, mitotic cell division, and endoreduplication, frequently occur in sequential yet overlapping manner during the development of the embryo and the endosperm, seed structures that are both products of double fertilization. Asymmetric cell divisions in the embryo generate polarized daughter cells with different cell fates. While nuclear and cell division cycles play a key role in determining final seed cell numbers, endoreduplication is often associated with processes such as cell enlargement and accumulation of storage metabolites that underlie cell differentiation and growth of the different seed compartments. This review focuses on recent advances in our understanding of different cell cycle mechanisms operating during seed development and their impact on the growth, development, and function of seed tissues. Particularly, the roles of core cell cycle regulators, such as cyclin-dependent-kinases and their inhibitors, the Retinoblastoma-Related/E2F pathway and the proteasome-ubiquitin system, are discussed in the contexts of different cell cycle types that characterize seed development. The contributions of nuclear and cellular proliferative cycles and endoreduplication to cereal endosperm development are also discussed.

  2. Molecular mechanisms controlling the cell cycle in embryonic stem cells.

    PubMed

    Abdelalim, Essam M

    2013-12-01

    Embryonic stem (ES) cells are originated from the inner cell mass of a blastocyst stage embryo. They can proliferate indefinitely, maintain an undifferentiated state (self-renewal), and differentiate into any cell type (pluripotency). ES cells have an unusual cell cycle structure, consists mainly of S phase cells, a short G1 phase and absence of G1/S checkpoint. Cell division and cell cycle progression are controlled by mechanisms ensuring the accurate transmission of genetic information from generation to generation. Therefore, control of cell cycle is a complicated process, involving several signaling pathways. Although great progress has been made on the molecular mechanisms involved in the regulation of ES cell cycle, many regulatory mechanisms remain unknown. This review summarizes the current knowledge about the molecular mechanisms regulating the cell cycle of ES cells and describes the relationship existing between cell cycle progression and the self-renewal.

  3. Experimental implementation of automatic 'cycle to cycle' control of a chiral simulated moving bed separation.

    PubMed

    Amanullah, Mohammad; Grossmann, Cristian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2007-09-21

    In the absence of a suitable controller, currently simulated moving beds (SMBs) are operated suboptimally to cope with system uncertainties and to guarantee robustness of operation. Recently, we have developed a 'cycle to cycle' optimizing controller that not only makes use of minimal system information, i.e. only the Henry constants and average bed voidage, but also optimizes the process performance and taps the full economic potential of the SMB technology. The experimental implementation of the 'cycle to cycle' optimizing controller had been carried out for achiral separation. For chiral separation however, application of any online controller has not been possible because an appropriate online monitoring system has not been available. This work reports and discusses the first experimental implementation of the 'cycle to cycle' optimizing control for chiral separations. A mixture of guaifenesin enantiomers is separated on Chiralcel OD columns with ethanol as mobile phase in a eight-column four sections laboratory SMB unit. The results show that the controller, although using minimal information about the retention of the two enantiomers, is able to meet product and process specifications, can optimize the process performance, and is capable of rejecting disturbances that may occur during the operation of the SMB plant.

  4. Prediction and control of limit cycling motions in boosting rockets

    NASA Astrophysics Data System (ADS)

    Newman, Brett

    An investigation concerning the prediction and control of observed limit cycling behavior in a boosting rocket is considered. The suspected source of the nonlinear behavior is the presence of Coulomb friction in the nozzle pivot mechanism. A classical sinusoidal describing function analysis is used to accurately recreate and predict the observed oscillatory characteristic. In so doing, insight is offered into the limit cycling mechanism and confidence is gained in the closed-loop system design. Nonlinear simulation results are further used to support and verify the results obtained from describing function theory. Insight into the limit cycling behavior is, in turn, used to adjust control system parameters in order to passively control the oscillatory tendencies. Tradeoffs with the guidance and control system stability/performance are also noted. Finally, active control of the limit cycling behavior, using a novel feedback algorithm to adjust the inherent nozzle sticking-unsticking characteristics, is considered.

  5. Bypass control valve seal and bearing life cycle test report

    NASA Technical Reports Server (NTRS)

    Lundback, A. V.

    1972-01-01

    The operating characteristics of a bypass control valve seal and bearing life cycle tests are reported. Data from the initial assembly, leak, torque, and deflection tests are included along with the cycle life test results and conclusions. The equipment involved was to be used in the nuclear engine for the rocket vehicles program.

  6. Dynamic translation regulation in Caulobacter cell cycle control.

    PubMed

    Schrader, Jared M; Li, Gene-Wei; Childers, W Seth; Perez, Adam M; Weissman, Jonathan S; Shapiro, Lucy; McAdams, Harley H

    2016-11-01

    Progression of the Caulobacter cell cycle requires temporal and spatial control of gene expression, culminating in an asymmetric cell division yielding distinct daughter cells. To explore the contribution of translational control, RNA-seq and ribosome profiling were used to assay global transcription and translation levels of individual genes at six times over the cell cycle. Translational efficiency (TE) was used as a metric for the relative rate of protein production from each mRNA. TE profiles with similar cell cycle patterns were found across multiple clusters of genes, including those in operons or in subsets of operons. Collections of genes associated with central cell cycle functional modules (e.g., biosynthesis of stalk, flagellum, or chemotaxis machinery) have consistent but different TE temporal patterns, independent of their operon organization. Differential translation of operon-encoded genes facilitates precise cell cycle-timing for the dynamic assembly of multiprotein complexes, such as the flagellum and the stalk and the correct positioning of regulatory proteins to specific cell poles. The cell cycle-regulatory pathways that produce specific temporal TE patterns are separate from-but highly coordinated with-the transcriptional cell cycle circuitry, suggesting that the scheduling of translational regulation is organized by the same cyclical regulatory circuit that directs the transcriptional control of the Caulobacter cell cycle.

  7. Dilution cycle control for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

    A dilution cycle control system for an absorption refrigeration system is disclosed. The control system includes a time delay relay for sensing shutdown of the absorption refrigeration system and for generating a control signal only after expiration of a preselected time period measured from the sensed shutdown of the absorption refrigeration system, during which the absorption refrigeration system is not restarted. A dilution cycle for the absorption refrigeration system is initiated in response to generation of a control signal by the time delay relay. This control system is particularly suitable for use with an absorption refrigeration system which is frequently cycled on and off since the time delay provided by the control system prevents needless dilution of the absorption refrigeration system when the system is turned off for only a short period of time and then is turned back on.

  8. Experimental implementation of automatic 'cycle to cycle' control to a nonlinear chiral simulated moving bed separation.

    PubMed

    Grossmann, Cristian; Langel, Christian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2010-03-26

    In order to better exploit the economic potential of the simulated moving bed chromatography a 'cycle to cycle' controller which only requires the information about the linear adsorption behavior and the overall average porosity of the columns has been proposed. Recently, an automated on-line HPLC monitoring system which determines the concentrations in the two product streams averaged over one cycle, and returns them as feedback information to the controller was implemented. The new system allows for an accurate determination of the average concentration of the product streams even if the plant is operated at high concentrations. This paper presents the experimental implementation of the 'cycle to cycle' control concept to the separation of guaifenesin enantiomers under nonlinear chromatographic conditions, i.e. at high feed concentrations. Different case studies have been carried out to challenge the controller under realistic operation conditions, e.g. introducing pump disturbances and changing the feed concentration during the operation. The experimental results clearly demonstrate that the controller can indeed deliver the specified purities and improve the process performance.

  9. Polymers with autonomous life-cycle control.

    PubMed

    Patrick, Jason F; Robb, Maxwell J; Sottos, Nancy R; Moore, Jeffrey S; White, Scott R

    2016-12-14

    The lifetime of man-made materials is controlled largely by the wear and tear of everyday use, environmental stress and unexpected damage, which ultimately lead to failure and disposal. Smart materials that mimic the ability of living systems to autonomously protect, report, heal and even regenerate in response to damage could increase the lifetime, safety and sustainability of many manufactured items. There are several approaches to achieving these functions using polymer-based materials, but making them work in highly variable, real-world situations is proving challenging.

  10. Polymers with autonomous life-cycle control

    NASA Astrophysics Data System (ADS)

    Patrick, Jason F.; Robb, Maxwell J.; Sottos, Nancy R.; Moore, Jeffrey S.; White, Scott R.

    2016-12-01

    The lifetime of man-made materials is controlled largely by the wear and tear of everyday use, environmental stress and unexpected damage, which ultimately lead to failure and disposal. Smart materials that mimic the ability of living systems to autonomously protect, report, heal and even regenerate in response to damage could increase the lifetime, safety and sustainability of many manufactured items. There are several approaches to achieving these functions using polymer-based materials, but making them work in highly variable, real-world situations is proving challenging.

  11. Control system options and strategies for supercritical CO2 cycles.

    SciTech Connect

    Moisseytsev, A.; Kulesza, K. P.; Sienicki, J. J.; Nuclear Engineering Division; Oregon State Univ.

    2009-06-18

    The Supercritical Carbon Dioxide (S-CO{sub 2}) Brayton Cycle is a promising alternative to Rankine steam cycle and recuperated gas Brayton cycle energy converters for use with Sodium-Cooled Fast Reactors (SFRs), Lead-Cooled Fast Reactors (LFRs), as well as other advanced reactor concepts. The S-CO{sub 2} Brayton Cycle offers higher plant efficiencies than Rankine or recuperated gas Brayton cycles operating at the same liquid metal reactor core outlet temperatures as well as reduced costs or size of key components especially the turbomachinery. A new Plant Dynamics Computer Code has been developed at Argonne National Laboratory for simulation of a S-CO{sub 2} Brayton Cycle energy converter coupled to an autonomous load following liquid metal-cooled fast reactor. The Plant Dynamics code has been applied to investigate the effectiveness of a control strategy for the S-CO{sub 2} Brayton Cycle for the STAR-LM 181 MWe (400 MWt) Lead-Cooled Fast Reactor. The strategy, which involves a combination of control mechanisms, is found to be effective for controlling the S-CO{sub 2} Brayton Cycle over the complete operating range from 0 to 100 % load for a representative set of transient load changes. While the system dynamic analysis of control strategy performance for STARLM is carried out for a S-CO{sub 2} Brayton Cycle energy converter incorporating an axial flow turbine and compressors, investigations of the S-CO{sub 2} Brayton Cycle have identified benefits from the use of centrifugal compressors which offer a wider operating range, greater stability near the critical point, and potentially further cost reductions due to fewer stages than axial flow compressors. Models have been developed at Argonne for the conceptual design and performance analysis of centrifugal compressors for use in the SCO{sub 2} Brayton Cycle. Steady state calculations demonstrate the wider operating range of centrifugal compressors versus axial compressors installed in a S-CO{sub 2} Brayton Cycle as

  12. Few-cycle plasmon oscillations controlling photoemission from metal nanoparticles

    SciTech Connect

    Földi, Péter; Márton, István; Német, Nikolett; Dombi, Péter; Ayadi, Viktor

    2015-01-05

    Few-cycle optical excitation of nanosystems holds promise of fundamental discoveries and applications in ultrafast nanoscience, the development of nanostructured photocathodes, and many more. For these, surface plasmon generation on unprecedented timescales needs to be controlled. For this, few-cycle plasmon oscillations on a metal nanoparticle can be generated by keeping considerable electric field enhancement factors. As an initial application of such a high spatiotemporal localization of an ultrashort laser pulse, we numerically demonstrate the control of photoelectrons on a true sub-fs timescale in nanometric spatial domains. We show that it is only off-resonant nanoparticles that can provide few-cycle plasmons and electron control on this timescale.

  13. Variable cycle stirling engine and gas leakage control system therefor

    SciTech Connect

    Otters, J.

    1984-12-25

    An improved thermal engine of the type having a displacer body movable between the hot end and the cold end of a chamber for subjecting a fluid within that chamber to a thermodynamic cycle and having a work piston driven by the fluid for deriving a useful work output. The work piston pumps a hydraulic fluid and a hydraulic control valve is connected in line with the hydraulic output conduit such that the flow of hydraulic fluid may be restricted to any desired degree or stopped altogether. The work piston can therefore be controlled by means of a controller device independently from the movement of the displacer such that a variety of engine cycles can be obtained for optimum engine efficiency under varying load conditions. While a Stirling engine cycle is particularly contemplated, other engine cycles may be obtained by controlling the movement of the displacer and work pistons. Also disclosed are a working gas recovery system for controlling leakage of working gas from the displacer chamber, and a compound work piston arrangement for preventing leakage of hydraulic fluid around the work piston into the displacer chamber.

  14. Strong hydrological control on nutrient cycling of subtropical rainforests

    NASA Astrophysics Data System (ADS)

    Lin, T. C.; Chang, C. T.; Huang, J. C.; Wang, L.; Lin, N. H.

    2016-12-01

    Forest nutrient cycling is strongly controlled by both biological and hydrological factors. However, based on a close examination of earlier reports, we highlight the role of hydrological control on nutrient cycling at a global scale and is more important at humid tropical and subtropical forests. we analyzed the nutrient budget of precipitation input and stream water output from 1994 to 2013 in a subtropical forest in Taiwan and conducted a data synthesis using results from 32 forests across the globe. The results revealed that monthly input and output of ions were positively correlated with water quantity, indicating hydrological control on nutrient cycling. Hydrological control is also evident from the greater ions export via stream water during the warm and wet growing season. The synthesis also illustrates that strong hydrological control leads to lower nitrogen retention and greater net loss of base cations in humid regions, particularly in the humid tropical and subtropical forests. Our result is of great significance in an era of global climate change because climate change could directly affect ecosystem nutrient cycling particularly in the tropics through changes in patterns of precipitation regime.

  15. Phosphorylation network dynamics in the control of cell cycle transitions.

    PubMed

    Fisher, Daniel; Krasinska, Liliana; Coudreuse, Damien; Novák, Béla

    2012-10-15

    Fifteen years ago, it was proposed that the cell cycle in fission yeast can be driven by quantitative changes in the activity of a single protein kinase complex comprising a cyclin - namely cyclin B - and cyclin dependent kinase 1 (Cdk1). When its activity is low, Cdk1 triggers the onset of S phase; when its activity level exceeds a specific threshold, it promotes entry into mitosis. This model has redefined our understanding of the essential functional inputs that organize cell cycle progression, and its main principles now appear to be applicable to all eukaryotic cells. But how does a change in the activity of one kinase generate ordered progression through the cell cycle in order to separate DNA replication from mitosis? To answer this question, we must consider the biochemical processes that underlie the phosphorylation of Cdk1 substrates. In this Commentary, we discuss recent findings that have shed light on how the threshold levels of Cdk1 activity that are required for progression through each phase are determined, how an increase in Cdk activity generates directionality in the cell cycle, and why cell cycle transitions are abrupt rather than gradual. These considerations lead to a general quantitative model of cell cycle control, in which opposing kinase and phosphatase activities have an essential role in ensuring dynamic transitions.

  16. Tectonic control of coastal onlap cycles, southwest Washington

    SciTech Connect

    Armentrout, J.M.

    1987-05-01

    Local coastal onlap and paleobiobathymetric curves for 14 sections define three Cenozoic depositional onlap-offlap cycles separated by regionally significant unconformities. A paleoclimatic curve for western Oregon and Washington, based on paleoecologic data sets, demonstrates that the local transgressions are coincident with cool climates and the regressions with warm climates, and are therefore not driven by glacioeustatic cycles. Comparison of the local coastal onlap and paleobiobathymetric curves with the global Cenozoic Cycle Chart (modified Exxon Sea Level Chart - May, 1986) further demonstrates the uniqueness of the western Washington curves. The global Cenozoic cycle Chart curve represents coastal onlap and sea level curves based on integration of both climate and tectonic variations. The non-parallel cycle pattern for southwest Washington suggests a unique tectonically forced system. Evidence derived from stratigraphic sequences, igneous rock geochemistry, radiometric dating, remnant magnetic patterns, sandstone provenance studies, and paleogeographic reconstructions is used to identify the tectonic events controlling the local depositional cycles. The principal events are (1) middle Eocene accretion of a seamount chain; (2) early-late Eocene westward relocation of subduction; (3) late Eocene onset of Cascade arc volcanism; (4) late-early Miocene plate readjustment due to back-arc extension in the Columbia River Plateau and Great Basin; and (5) late Pliocene to early Pleistocene northeast compression forced by continued subduction of remnants of the Kula Plate beneath North America.

  17. Tune-control improvements on the rapid-cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-01-01

    The as-built lattice of the Rapid-Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. A set of octupole magnets and programmable power supplies with similar dynamic qualities have been constructed and installed to control the anticipated high-intensity transverse instability. This system will be operational in the spring of 1981.

  18. Cell cycle control, checkpoint mechanisms, and genotoxic stress.

    PubMed Central

    Shackelford, R E; Kaufmann, W K; Paules, R S

    1999-01-01

    The ability of cells to maintain genomic integrity is vital for cell survival and proliferation. Lack of fidelity in DNA replication and maintenance can result in deleterious mutations leading to cell death or, in multicellular organisms, cancer. The purpose of this review is to discuss the known signal transduction pathways that regulate cell cycle progression and the mechanisms cells employ to insure DNA stability in the face of genotoxic stress. In particular, we focus on mammalian cell cycle checkpoint functions, their role in maintaining DNA stability during the cell cycle following exposure to genotoxic agents, and the gene products that act in checkpoint function signal transduction cascades. Key transitions in the cell cycle are regulated by the activities of various protein kinase complexes composed of cyclin and cyclin-dependent kinase (Cdk) molecules. Surveillance control mechanisms that check to ensure proper completion of early events and cellular integrity before initiation of subsequent events in cell cycle progression are referred to as cell cycle checkpoints and can generate a transient delay that provides the cell more time to repair damage before progressing to the next phase of the cycle. A variety of cellular responses are elicited that function in checkpoint signaling to inhibit cyclin/Cdk activities. These responses include the p53-dependent and p53-independent induction of Cdk inhibitors and the p53-independent inhibitory phosphorylation of Cdk molecules themselves. Eliciting proper G1, S, and G2 checkpoint responses to double-strand DNA breaks requires the function of the Ataxia telangiectasia mutated gene product. Several human heritable cancer-prone syndromes known to alter DNA stability have been found to have defects in checkpoint surveillance pathways. Exposures to several common sources of genotoxic stress, including oxidative stress, ionizing radiation, UV radiation, and the genotoxic compound benzo[a]pyrene, elicit cell cycle

  19. New algorithm to control a cycle ergometer using electrical stimulation.

    PubMed

    Petrofsky, J S

    2003-01-01

    Data were collected from four male subjects to determine the relationships between load, speed and muscle use during cycle ergometry. These data were then used to construct equations to govern the stimulation of muscle in paralysed individuals, during cycle ergometry induced by functional electrical stimulation (FES) of the quadriceps, gluteus maximus and hamstring muscles. The algorithm was tested on four subjects who were paralysed owing to a complete spinal cord injury between T4 and T11. Using the multivariate equation, the control of movement was improved, and work was accomplished that was double (2940 Nm min(-1) compared with 5880 Nm min(-1)) that of traditional FES cycle ergometry, when muscle stimulation was also controlled by electrical stimulation. Stress on the body, assessed by cardiac output, was increased almost two-fold during maximum work with the new algorithm (81 min(-1) compared with 15 l min(-1) with the new algorithm). These data support the concept that the limitation to workload that a person can achieve on FES cycle ergometry is in the control equations and not in the paralysed muscle.

  20. Tune control improvements on the rapid cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-06-01

    The as-built lattice of the Rapid Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. 5 refs.

  1. Transpiration during life cycle in controlled wheat growth

    NASA Technical Reports Server (NTRS)

    Volk, Tyler; Rummel, John D.

    1989-01-01

    A previously-developed model of wheat growth, designed for convenient incorporation into system-level models of advanced space life support systems is described. The model is applied to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. The adequacy of modeling the transpiration as proportional to the inedible biomass, and an age factor which varies during the life cycle, are examined. Results indicate that during the main phase of vegetative growth in the first half of the life cycle, the rate of transpiration per unit mass of inedible biomass is more than double the rate during the phase of grain development and maturation during latter half of the life cycle.

  2. Quantum thermodynamic processes: a control theory for machine cycles

    NASA Astrophysics Data System (ADS)

    Birjukov, J.; Jahnke, T.; Mahler, G.

    2008-07-01

    The minimal set of thermodynamic control parameters consists of a statistical (thermal) and a mechanical one. These suffice to introduce all the pertinent thermodynamic variables; thermodynamic processes can then be defined as paths on this 2-dimensional control plane. Putting aside coherence we show that for a large class of quantum objects with discrete spectra and for the cycles considered the Carnot efficiency applies as a universal upper bound. In the dynamic (finite time) regime renormalized thermodynamic variables allow to include non-equilibrium phenomena in a systematic way. The machine function ceases to exist in the large speed limit; the way, in which this limit is reached, depends on the type of cycle considered.

  3. Transpiration during life cycle in controlled wheat growth

    NASA Technical Reports Server (NTRS)

    Volk, Tyler; Rummel, John D.

    1990-01-01

    A previously developed model of wheat growth, designed for convenient incorporation into system level models of advanced space life support systems is described. The model is applied to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. The adequacy of modeling the transpiration as proportional to the inedible biomass and an age factor that varies during the life cycle are discussed.

  4. Cell cycle-dependent control of homologous recombination.

    PubMed

    Zhao, Xin; Wei, Chengwen; Li, Jingjing; Xing, Poyuan; Li, Jingyao; Zheng, Sihao; Chen, Xuefeng

    2017-08-01

    DNA double-strand breaks (DSBs) are among the most deleterious type of DNA lesions threatening genome integrity. Homologous recombination (HR) and non-homologous end joining (NHEJ) are two major pathways to repair DSBs. HR requires a homologous template to direct DNA repair, and is generally recognized as a high-fidelity pathway. In contrast, NHEJ directly seals broken ends, but the repair product is often accompanied by sequence alterations. The choice of repair pathways is strictly controlled by the cell cycle. The occurrence of HR is restricted to late S to G2 phases while NHEJ operates predominantly in G1 phase, although it can act throughout most of the cell cycle. Deregulation of repair pathway choice can result in genotoxic consequences associated with cancers. How the cell cycle regulates the choice of HR and NHEJ has been extensively studied in the past decade. In this review, we will focus on the current progresses on how HR is controlled by the cell cycle in both Saccharomyces cerevisiae and mammals. Particular attention will be given to how cyclin-dependent kinases modulate DSB end resection, DNA damage checkpoint signaling, repair and processing of recombination intermediates. In addition, we will discuss recent findings on how HR is repressed in G1 and M phases by the cell cycle. © The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. On controlling networks of limit-cycle oscillators.

    PubMed

    Skardal, Per Sebastian; Arenas, Alex

    2016-09-01

    The control of network-coupled nonlinear dynamical systems is an active area of research in the nonlinear science community. Coupled oscillator networks represent a particularly important family of nonlinear systems, with applications ranging from the power grid to cardiac excitation. Here, we study the control of network-coupled limit cycle oscillators, extending the previous work that focused on phase oscillators. Based on stabilizing a target fixed point, our method aims to attain complete frequency synchronization, i.e., consensus, by applying control to as few oscillators as possible. We develop two types of controls. The first type directs oscillators towards larger amplitudes, while the second does not. We present numerical examples of both control types and comment on the potential failures of the method.

  6. On controlling networks of limit-cycle oscillators

    NASA Astrophysics Data System (ADS)

    Skardal, Per Sebastian; Arenas, Alex

    2016-09-01

    The control of network-coupled nonlinear dynamical systems is an active area of research in the nonlinear science community. Coupled oscillator networks represent a particularly important family of nonlinear systems, with applications ranging from the power grid to cardiac excitation. Here, we study the control of network-coupled limit cycle oscillators, extending the previous work that focused on phase oscillators. Based on stabilizing a target fixed point, our method aims to attain complete frequency synchronization, i.e., consensus, by applying control to as few oscillators as possible. We develop two types of controls. The first type directs oscillators towards larger amplitudes, while the second does not. We present numerical examples of both control types and comment on the potential failures of the method.

  7. Control system development for an organic Ranking cycle engine

    NASA Technical Reports Server (NTRS)

    Bergthold, F. M., Jr.; Fulton, D. G.; Haskins, H. J.

    1981-01-01

    An organic Rankine cycle engine is used as part of a solar thermal power conversion assembly (PCA). The PCA, including a direct-heated cavity receiver and a shaft-mounted alternator, is mounted at the focal point of a parabolic dish concentrator. The engine controls are required to maintain approximately constant values of turbine inlet temperature and shaft speed, despite variation in the concentrated solar power input to the receiver. The controls design approach, system models, and initial stability and performance analysis results are presented herein.

  8. Price controls for medical innovations in a life cycle perspective.

    PubMed

    Sorek, Gilad

    2014-01-01

    We study the market for new medical technologies from a life cycle perspective, incorporating the fact that healthcare utilization is biased towards old age. Contrary to conventional wisdom, we find that price controls on medical innovations can expand investment in medical R&D and results in Pareto superior social outcomes, a consequence of the price controls' ability to increase saving. Importantly, this finding occurs only when the price cap regime is extensive: selective regulation on few technologies - such as pharmaceuticals alone - have the conventional negative effect on innovation. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Neural control of rhythmic arm cycling after stroke

    PubMed Central

    Loadman, Pamela M.; Hundza, Sandra R.

    2012-01-01

    Disordered reflex activity and alterations in the neural control of walking have been observed after stroke. In addition to impairments in leg movement that affect locomotor ability after stroke, significant impairments are also seen in the arms. Altered neural control in the upper limb can often lead to altered tone and spasticity resulting in impaired coordination and flexion contractures. We sought to address the extent to which the neural control of movement is disordered after stroke by examining the modulation pattern of cutaneous reflexes in arm muscles during arm cycling. Twenty-five stroke participants who were at least 6 mo postinfarction and clinically stable, performed rhythmic arm cycling while cutaneous reflexes were evoked with trains (5 × 1.0-ms pulses at 300 Hz) of constant-current electrical stimulation to the superficial radial (SR) nerve at the wrist. Both the more (MA) and less affected (LA) arms were stimulated in separate trials. Bilateral electromyography (EMG) activity was recorded from muscles acting at the shoulder, elbow, and wrist. Analysis was conducted on averaged reflexes in 12 equidistant phases of the movement cycle. Phase-modulated cutaneous reflexes were present, but altered, in both MA and LA arms after stroke. Notably, the pattern was “blunted” in the MA arm in stroke compared with control participants. Differences between stroke and control were progressively more evident moving from shoulder to wrist. The results suggest that a reduced pattern of cutaneous reflex modulation persists during rhythmic arm movement after stroke. The overall implication of this result is that the putative spinal contributions to rhythmic human arm movement remain accessible after stroke, which has translational implications for rehabilitation. PMID:22572949

  10. Method for Controlling Space Transportation System Life Cycle Costs

    NASA Technical Reports Server (NTRS)

    McCleskey, Carey M.; Bartine, David E.

    2006-01-01

    A structured, disciplined methodology is required to control major cost-influencing metrics of space transportation systems during design and continuing through the test and operations phases. This paper proposes controlling key space system design metrics that specifically influence life cycle costs. These are inclusive of flight and ground operations, test, and manufacturing and infrastructure. The proposed technique builds on today's configuration and mass properties control techniques and takes on all the characteristics of a classical control system. While the paper does not lay out a complete math model, key elements of the proposed methodology are explored and explained with both historical and contemporary examples. Finally, the paper encourages modular design approaches and technology investments compatible with the proposed method.

  11. Integrated gasification combined cycle: Commercial option for acid rain control

    SciTech Connect

    Simbeck, D.R.; Dickenson, R.L.

    1985-01-01

    The overwhelming success of the Cool Water integrated gasification combined cycle (IGCC) electric power generation plant has re-defined coal gasification as a commercial option for acid rain control. This 120 MW facility emits less than 0.034 pounds SO/sub x/ and 0.059 pounds NO/sub x/ per million Btu feed coal. The potential of IGCC for new power plants is more clear-cut than for acid rain control because the acid rain issue currently involves existing power plants. Traditionally, coal gasification has been ignored as a technology option for acid rain control on existing coal-fired boilers. This paper analyzes coal gasification as an economically attractive option for significant SO/sub x/ and NO/sub x/ reduction in existing power plants.

  12. Combinatorial Gene Regulation through Kinetic Control of the Transcription Cycle.

    PubMed

    Scholes, Clarissa; DePace, Angela H; Sánchez, Álvaro

    2017-01-25

    Cells decide when, where, and to what level to express their genes by "computing" information from transcription factors (TFs) binding to regulatory DNA. How is the information contained in multiple TF-binding sites integrated to dictate the rate of transcription? The dominant conceptual and quantitative model is that TFs combinatorially recruit one another and RNA polymerase to the promoter by direct physical interactions. Here, we develop a quantitative framework to explore kinetic control, an alternative model in which combinatorial gene regulation can result from TFs working on different kinetic steps of the transcription cycle. Kinetic control can generate a wide range of analog and Boolean computations without requiring the input TFs to be simultaneously bound to regulatory DNA. We propose experiments that will illuminate the role of kinetic control in transcription and discuss implications for deciphering the cis-regulatory "code."

  13. Cell Cycle Programs of Gene Expression Control Morphogenetic Protein Localization

    PubMed Central

    Lord, Matthew; Yang, Melody C.; Mischke, Michelle; Chant, John

    2000-01-01

    Genomic studies in yeast have revealed that one eighth of genes are cell cycle regulated in their expression. Almost without exception, the significance of cell cycle periodic gene expression has not been tested. Given that many such genes are critical to cellular morphogenesis, we wanted to examine the importance of periodic gene expression to this process. The expression profiles of two genes required for the axial pattern of cell division, BUD3 and BUD10/AXL2/SRO4, are strongly cell cycle regulated. BUD3 is expressed close to the onset of mitosis. BUD10 is expressed in late G1. Through promotor-swap experiments, the expression profile of each gene was altered and the consequences examined. We found that an S/G2 pulse of BUD3 expression controls the timing of Bud3p localization, but that this timing is not critical to Bud3p function. In contrast, a G1 pulse of BUD10 expression plays a direct role in Bud10p localization and function. Bud10p, a membrane protein, relies on the polarized secretory machinery specific to G1 to be delivered to its proper location. Such a secretion-based targeting mechanism for membrane proteins provides cells with flexibility in remodeling their architecture or evolving new forms. PMID:11134078

  14. Inspiratory resistive loading improves cycling capacity: a placebo controlled trial

    PubMed Central

    Gething, A; Williams, M; Davies, B

    2004-01-01

    Background: Respiratory muscle training has been shown to improve both its strength and endurance. The effect of these improvements on whole-body exercise performance remains controversial. Objective: To assess the effect of a 10 week inspiratory resistive loading (IRL) intervention on respiratory muscle performance and whole-body exercise endurance. Methods: Fifteen apparently healthy subjects (10 men, 5 women) were randomly allocated to one of three groups. One group underwent IRL set at 80% of maximum inspiratory pressure with ever decreasing work/rest ratios until task failure, for three days a week for 10 weeks (IRL group). A second placebo group performed the same training procedure but with a minimal resistance (PLA group). IRL and placebo training were performed at rest. The remaining five control subjects performed no IRL during the 10 week study period (CON group). Cycling endurance capacity at 75% V·O2peak was measured before and after the intervention. Results: After the 10 week IRL intervention, respiratory muscle strength (maximum inspiratory pressure) and endurance (sum of sustained maximum inspiratory pressure) had significantly improved (by 34% and 38% respectively). An increase in diaphragm thickness was also observed. These improvements translated into a 36% increase in cycling time to exhaustion at 75% V·O2peak. During cycling trials, heart rate, ventilation, and rating of perceived exertion were attenuated in the IRL group. No changes were observed for the PLA or CON group either in the time to exhaustion or cardiorespiratory response to the same intensity of exercise. Conclusion: Ten weeks of IRL attenuated the heart rate, ventilatory, and perceptual response to constant workload exercise, and improved the cycling time to exhaustion. Familiarisation was not a factor and the placebo effect was minimal. PMID:15562168

  15. Model Predictive Control of Integrated Gasification Combined Cycle Power Plants

    SciTech Connect

    B. Wayne Bequette; Priyadarshi Mahapatra

    2010-08-31

    The primary project objectives were to understand how the process design of an integrated gasification combined cycle (IGCC) power plant affects the dynamic operability and controllability of the process. Steady-state and dynamic simulation models were developed to predict the process behavior during typical transients that occur in plant operation. Advanced control strategies were developed to improve the ability of the process to follow changes in the power load demand, and to improve performance during transitions between power levels. Another objective of the proposed work was to educate graduate and undergraduate students in the application of process systems and control to coal technology. Educational materials were developed for use in engineering courses to further broaden this exposure to many students. ASPENTECH software was used to perform steady-state and dynamic simulations of an IGCC power plant. Linear systems analysis techniques were used to assess the steady-state and dynamic operability of the power plant under various plant operating conditions. Model predictive control (MPC) strategies were developed to improve the dynamic operation of the power plants. MATLAB and SIMULINK software were used for systems analysis and control system design, and the SIMULINK functionality in ASPEN DYNAMICS was used to test the control strategies on the simulated process. Project funds were used to support a Ph.D. student to receive education and training in coal technology and the application of modeling and simulation techniques.

  16. An Animal-Like Cryptochrome Controls the Chlamydomonas Sexual Cycle.

    PubMed

    Zou, Yong; Wenzel, Sandra; Müller, Nico; Prager, Katja; Jung, Elke-Martina; Kothe, Erika; Kottke, Tilman; Mittag, Maria

    2017-07-01

    Cryptochromes are known as flavin-binding blue light receptors in bacteria, fungi, plants, and insects. The animal-like cryptochrome (aCRY) of the green alga Chlamydomonas reinhardtii has extended our view on cryptochromes, because it responds also to other wavelengths of the visible spectrum, including red light. Here, we have investigated if aCRY is involved in the regulation of the sexual life cycle of C. reinhardtii, which is controlled by blue and red light at the steps of gametogenesis along with its restoration and germination. We show that aCRY is differentially expressed not only during the life cycle but also within the cell as part of the soluble and/or membrane-associated protein fraction. Moreover, localization of aCRY within the algal cell body varies between vegetative cells and the different cell types of gametogenesis. aCRY is significantly (early day) or to a small extent (late night) enriched in the nucleus in vegetative cells. In pregametes, gametes and dark-inactivated gametes, aCRY is localized over the cell body. aCRY plays an important role in the sexual life cycle of C. reinhardtii: It controls the germination of the alga, under which the zygote undergoes meiosis, in a positive manner, similar to the regulation by the blue light receptors phototropin and plant cryptochrome (pCRY). However, aCRY acts in combination with pCRY as a negative regulator for mating ability as well as for mating maintenance, opposite to the function of phototropin in these processes. © 2017 American Society of Plant Biologists. All Rights Reserved.

  17. ASDTIC duty-cycle control for power converters

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Schoenfeld, A. D.

    1972-01-01

    The application of analog signal to discrete interval converter (ASDTIC), a hybrid micromodule, two loop control subsystem, to a switching, stepdown dc to dc converter is described. The power circuitry, interface and ASDTIC subsystems used in this switching regulator were developed to exhibit the improved regulation, transient performance, regulator stability and freedom from the effects of variations in parts characteristics due to environmental changes and aging. ASDTIC can be used with other types of power circuits that use duty-cycle control techniques by simple changes in the interface subsystem. The circuitry and performance characteristics of a +10V dc switching converter as well as that of the ASDTIC micromodule are described. Realization of the ASDTIC hybrid micromodule has been accomplished with a hermetically sealed, beam-lead, bonded/deposited nichrome thin film resistors, discrete capacitors and integrated circuits on dilithic, glazed alumina substrates using 22 feed through terminals in an integrated package.

  18. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow can modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields.

  19. Optimal digital control of a Stirling cycle cooler

    NASA Technical Reports Server (NTRS)

    Feeley, J.; Feeley, P.; Langford, G.

    1990-01-01

    This short paper describes work in progress on the conceptual design of a control system for a cryogenic cooler intended for use aboard spacecraft. The cooler will produce 5 watts of cooling at 65 K and will be used to support experiments associated with the following: earth observation; atmospheric measurements; infrared, x-ray, and gamma-ray astronomy; and magnetic field characterization. The cooler has been designed and constructed for NASA/GSFC by Philips Laboratories and is described in detail. The cooler has a number of unique design features intended to enhance long life and maintenance free operation in space including use of the high efficiency Stirling thermodynamic refrigeration cycle, linear magnetic motors, clearance-seals, and magnetic bearings. The proposed control system design is based on optimal control theory and is targeted for custom integrated circuit implementation. The resulting control system will meet the following mission requirements: efficiency, reliability, optimal thermodynamic, electrical, and mechanical performance; freedom from operator intervention; light weight; and small size.

  20. Long-term litter decomposition controlled by manganese redox cycling.

    PubMed

    Keiluweit, Marco; Nico, Peter; Harmon, Mark E; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

    2015-09-22

    Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn(2+) provided by fresh plant litter to produce oxidative Mn(3+) species at sites of active decay, with Mn eventually accumulating as insoluble Mn(3+/4+) oxides. Formation of reactive Mn(3+) species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn(3+)-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn(3+) species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant-soil system may have a profound impact on litter decomposition rates.

  1. Long-term litter decomposition controlled by manganese redox cycling

    PubMed Central

    Keiluweit, Marco; Nico, Peter; Harmon, Mark E.; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

    2015-01-01

    Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn2+ provided by fresh plant litter to produce oxidative Mn3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn3+/4+ oxides. Formation of reactive Mn3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn3+-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn3+ species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant–soil system may have a profound impact on litter decomposition rates. PMID:26372954

  2. Body Temperature Cycles Control Rhythmic Alternative Splicing in Mammals.

    PubMed

    Preußner, Marco; Goldammer, Gesine; Neumann, Alexander; Haltenhof, Tom; Rautenstrauch, Pia; Müller-McNicoll, Michaela; Heyd, Florian

    2017-08-03

    The core body temperature of all mammals oscillates with the time of the day. However, direct molecular consequences of small, physiological changes in body temperature remain largely elusive. Here we show that body temperature cycles drive rhythmic SR protein phosphorylation to control an alternative splicing (AS) program. A temperature change of 1°C is sufficient to induce a concerted splicing switch in a large group of functionally related genes, rendering this splicing-based thermometer much more sensitive than previously described temperature-sensing mechanisms. AS of two exons in the 5' UTR of the TATA-box binding protein (Tbp) highlights the general impact of this mechanism, as it results in rhythmic TBP protein levels with implications for global gene expression in vivo. Together our data establish body temperature-driven AS as a core clock-independent oscillator in mammalian peripheral clocks. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Space Transportation Systems Life Cycle Cost Assessment and Control

    NASA Technical Reports Server (NTRS)

    Robinson, John W.; Rhodes, Russell E.; Zapata, Edgar; Levack, Daniel J. H.; Donahue, Benjaamin B.; Knuth, William

    2008-01-01

    Civil and military applications of space transportation have been pursued for just over 50 years and there has been, and still is, a need for safe, dependable, affordable, and sustainable space transportation systems. Fully expendable and partially reusable space transportation systems have been developed and put in operation that have not adequately achieved this need. Access to space is technically achievable, but presently very expensive and will remain so until there is a breakthrough in the way we do business. Since 1991 the national Space Propulsion Synergy Team (SPST) has reviewed and assessed the lessons learned from the major U.S. space programs of the past decades focusing on what has been learned from the assessment and control of Life Cycle Cost (LCC) from these systems. This paper presents the results of a selected number of studies and analyses that have been conducted by the SPST addressing the need, as well as the solutions, for improvement in LCC. The major emphasis of the SPST processes is on developing the space transportation system requirements first (up front). These requirements must include both the usual system flight performance requirements and also the system functional requirements, including the infrastructure on Earth's surface, in-space and on the Moon and Mars surfaces to determine LCC. This paper describes the development of specific innovative engineering and management approaches and processes. This includes a focus on flight hardware maturity for reliability, ground operations approaches, and business processes between contractor and government organizations. A major change in program/project cost control is being proposed by the SPST to achieve a sustainable space transportation system LCC - controlling cost as a program metric in addition to the existing practice of controlling performance and weight. Without a firm requirement and methodically structured cost control, it is unlikely that an affordable and sustainable space

  4. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow should also modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields. The observational evidence and the theoretical consequences (similar to those of Cameron and Schussler (2012)) will be described.

  5. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    NASA Astrophysics Data System (ADS)

    Hathaway, David H.; Upton, L.

    2013-07-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow should also modulate the amplitude of the following sunspot cycle through its influence on the Sun’s polar fields. The observational evidence and the theoretical consequences (similar to those of Cameron and Schussler (2012)) will be described. Komm, Howard, and Harvey (1993) Solar Phys. 147, 207. Cameron and Schussler (2012) Astron. Astrophys. 548, A57.

  6. Long-term litter decomposition controlled by manganese redox cycling

    DOE PAGES

    Keiluweit, Marco; Nico, Peter S.; Harmon, Mark; ...

    2015-09-08

    Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of littermore » was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn2+ provided by fresh plant litter to produce oxidative Mn3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn3+/4+ oxides. Formation of reactive Mn3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn3+-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn3+ species in the litter layer. As a result, this observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant–soil system may have a profound impact on litter decomposition rates.« less

  7. Reverse the curse - the role of deubiquitination in cell cycle control

    PubMed Central

    Song, Ling; Rape, Michael

    2008-01-01

    Reversible protein ubiquitination is a crucial mechanism regulating the progression through the eukaryotic cell cycle. Ubiquitin-dependent signaling is terminated by specific deubiquitinating enzymes (DUBs), which now are known to be integral components of the core cell cycle machinery and cell cycle checkpoints. The importance of DUBs for cell cycle control is underscored by their frequent misregulation in cancer. Here, we discuss the role of deubiquitinating enzymes in controlling proliferation. PMID:18346885

  8. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Optical and thermal-fluid evaluation

    DOE PAGES

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; ...

    2016-05-30

    In single phase performance and appealing thermo-physical properties supercritical carbon dioxide (s-CO2) make a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ~973 K is required in order to merge CSP and s-CO2 Brayton cycle technologies. A coupled optical and thermal-fluid modeling effort for a tubular receiver is undertaken to evaluate the direct tubular s-CO2 receiver’s thermal performance when exposed to a concentrated solar power input of ~0.3–0.5 MW. Ray tracing, using SolTrace, is performed to determine the heat flux profiles on the receivermore » and computational fluid dynamics (CFD) determines the thermal performance of the receiver under the specified heating conditions. Moreover, an in-house MATLAB code is developed to couple SolTrace and ANSYS Fluent. CFD modeling is performed using ANSYS Fluent to predict the thermal performance of the receiver by evaluating radiation and convection heat loss mechanisms. Understanding the effects of variation in heliostat aiming strategy and flow configurations on the thermal performance of the receiver was achieved through parametric analyses. Finally, a receiver thermal efficiency ~85% was predicted and the surface temperatures were observed to be within the allowable limit for the materials under consideration.« less

  9. An Application of Invertibility of Boolean Control Networks to the Control of the Mammalian Cell Cycle.

    PubMed

    Zhang, Kuize; Zhang, Lijun; Mou, Shaoshuai

    2017-01-01

    In Fauré et al. (2006), the dynamics of the core network regulating the mammalian cell cycle is formulated as a Boolean control network (BCN) model consisting of nine proteins as state nodes and a tenth protein (protein CycD) as the control input node. In this model, one of the state nodes, protein Cdc20, plays a central role in the separation of sister chromatids. Hence, if any Cdc20 sequence can be obtained, fully controlling the mammalian cell cycle is feasible. Motivated by this fact, we study whether any Cdc20 sequence can be obtained theoretically. We formulate the foregoing problem as the invertibility of BCNs, that is, whether one can obtain any Cdc20 sequence by designing input (i.e., protein CycD) sequences. We give an algorithm to verify the invertibility of any BCN, and find that the BCN model for the core network regulating the mammalian cell cycle is not invertible, that is, one cannot obtain any Cdc20 sequence. We further present another algorithm to test whether a finite Cdc20 sequence can be generated by the BCN model, which leads to a series of periodic infinite Cdc20 sequences with alternately active and inactive Cdc20 segments. States of these sequences are alternated between the two attractors in the proposed model, which reproduces correctly how a cell exits the cell cycle to enter the quiescent state, or the opposite.

  10. Apicomplexan cell cycle flexibility: centrosome controls the clutch

    PubMed Central

    Chen, Chun-Ti; Gubbels, Marc-Jan

    2015-01-01

    The centrosome serves as a central hub coordinating multiple cellular events in eukaryotes. A recent study in Toxoplasma gondii revealed a unique bipartite structure of the centrosome, which coordinates the nuclear cycle (S-phase and mitosis) and budding cycle (cytokinesis) of the parasite, and deciphers the principle behind flexible apicomplexan cell division modes. PMID:25899747

  11. Cell cycle controls stress response and longevity in C. elegans

    PubMed Central

    Dottermusch, Matthias; Lakner, Theresa; Peyman, Tobias; Klein, Marinella; Walz, Gerd; Neumann-Haefelin, Elke

    2016-01-01

    Recent studies have revealed a variety of genes and mechanisms that influence the rate of aging progression. In this study, we identified cell cycle factors as potent regulators of health and longevity in C. elegans. Focusing on the cyclin-dependent kinase 2 (cdk-2) and cyclin E (cye-1), we show that inhibition of cell cycle genes leads to tolerance towards environmental stress and longevity. The reproductive system is known as a key regulator of longevity in C. elegans. We uncovered the gonad as the central organ mediating the effects of cell cycle inhibition on lifespan. In particular, the proliferating germ cells were essential for conferring longevity. Steroid hormone signaling and the FOXO transcription factor DAF-16 were required for longevity associated with cell cycle inhibition. Furthermore, we discovered that SKN-1 (ortholog of mammalian Nrf proteins) activates protective gene expression and induces longevity when cell cycle genes are inactivated. We conclude that both, germline absence and inhibition through impairment of cell cycle machinery results in longevity through similar pathways. In addition, our studies suggest further roles of cell cycle genes beyond cell cycle progression and support the recently described connection of SKN-1/Nrf to signals deriving from the germline. PMID:27668945

  12. Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

    1995-01-01

    Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed

  13. Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

    1995-01-01

    Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed

  14. Basal p21 controls population heterogeneity in cycling and quiescent cell cycle states

    PubMed Central

    Overton, K. Wesley; Spencer, Sabrina L.; Noderer, William L.; Meyer, Tobias; Wang, Clifford L.

    2014-01-01

    Phenotypic heterogeneity within a population of genetically identical cells is emerging as a common theme in multiple biological systems, including human cell biology and cancer. Using live-cell imaging, flow cytometry, and kinetic modeling, we showed that two states—quiescence and cell cycling—can coexist within an isogenic population of human cells and resulted from low basal expression levels of p21, a Cyclin-dependent kinase (CDK) inhibitor (CKI). We attribute the p21-dependent heterogeneity in cell cycle activity to double-negative feedback regulation involving CDK2, p21, and E3 ubiquitin ligases. In support of this mechanism, analysis of cells at a point before cell cycle entry (i.e., before the G1/S transition) revealed a p21–CDK2 axis that determines quiescent and cycling cell states. Our findings suggest a mechanistic role for p21 in generating heterogeneity in both normal tissues and tumors. PMID:25267623

  15. Control of cell cycle and cell growth by molecular chaperones.

    PubMed

    Aldea, Martí; Garí, Eloi; Colomina, Neus

    2007-11-01

    Cells adapt their size to both intrinsic and extrinsic demands and, among them, those that stem from growth and proliferation rates are crucial for cell size homeostasis. Here we revisit mechanisms that regulate cell cycle and cell growth in budding yeast. Cyclin Cln3, the most upstream activator of Start, is retained at the endoplasmic reticulum in early G(1) and released by specific chaperones in late G(1) to initiate the cell cycle. On one hand, these chaperones are rate-limiting for release of Cln3 and cell cycle entry and, on the other hand, they are required for key biosynthetic processes. We propose a model whereby the competition for specialized chaperones between growth and cycle machineries could gauge biosynthetic rates and set a critical size threshold at Start.

  16. Evaluation and Optimization of a Supercritical Carbon Dioxide Power Conversion Cycle for Nuclear Applications

    SciTech Connect

    Edwin A. Harvego; Michael G. McKellar

    2011-05-01

    There have been a number of studies involving the use of gases operating in the supercritical mode for power production and process heat applications. Supercritical carbon dioxide (CO2) is particularly attractive because it is capable of achieving relatively high power conversion cycle efficiencies in the temperature range between 550°C and 750°C. Therefore, it has the potential for use with any type of high-temperature nuclear reactor concept, assuming reactor core outlet temperatures of at least 550°C. The particular power cycle investigated in this paper is a supercritical CO2 Recompression Brayton Cycle. The CO2 Recompression Brayton Cycle can be used as either a direct or indirect power conversion cycle, depending on the reactor type and reactor outlet temperature. The advantage of this cycle when compared to the helium Brayton Cycle is the lower required operating temperature; 550°C versus 850°C. However, the supercritical CO2 Recompression Brayton Cycle requires an operating pressure in the range of 20 MPa, which is considerably higher than the required helium Brayton cycle operating pressure of 8 MPa. This paper presents results of analyses performed using the UniSim process analyses software to evaluate the performance of the supercritical CO2 Brayton Recompression Cycle for different reactor outlet temperatures. The UniSim model assumed a 600 MWt reactor power source, which provides heat to the power cycle at a maximum temperature of between 550°C and 750°C. The UniSim model used realistic component parameters and operating conditions to model the complete power conversion system. CO2 properties were evaluated, and the operating range for the cycle was adjusted to take advantage of the rapidly changing conditions near the critical point. The UniSim model was then optimized to maximize the power cycle thermal efficiency at the different maximum power cycle operating temperatures. The results of the analyses showed that power cycle thermal

  17. Mineralogical Controls on Carbon Cycling in a Floodplain Environment

    NASA Astrophysics Data System (ADS)

    Arora, B.; Dwivedi, D.; Steefel, C. I.; Spycher, N.; Fox, P. M.; Nico, P. S.

    2016-12-01

    With the overarching goal of understanding mineral-organic-microbe interactions on carbon and nutrient cycles, we are developing a reactive transport model that includes carbon (C) pools and transformations, a realistic treatment of protected C pools, multiple decomposition pathways, and radiocarbon (14C) dynamics. The objective of the modeling is to understand the impact of mineralogy on carbon turnover and residence times in a floodplain site in Rifle, CO. Previous studies have identified naturally reduced zones (NRZs) in the saturated zone of the Rifle site to be C hotspots and regions characterized by diffusion-limited transport and high rates of microbially-mediated biogeochemical reactions. Detailed characterization of the soil organic matter in both the NRZ and non-NRZ sediments at the Rifle site including radiocarbon dating, and extraction and chemical characterization of mineral-bound pool of organic matter, is used to inform the modeling. In this study, we describe the development of a coupled unsaturated-saturated flow and biogeochemical reactive transport model of the Rifle site along a two-dimensional cross-section (parallel to groundwater flow). The biogeochemical reaction network includes representations of bacterial and fungal activity, archetypal polymer and monomer carbon substrate groups, kinetic and equilibrium mineral precipitation and dissolution reactions, and aqueous and surface complexation. We use this model to explore fungal and bacterial community emergence at the site and compare organo-mineral interactions across NRZ and non-NRZ regions. Observed 14C profiles suggest that sediment-associated carbon in NRZ locations is much older than both the depositional age of the floodplain sediments and dissolved organic carbon in the groundwater. Model simulations were able to capture the observed soil organic matter (SOM) and ∆14C profiles across the Rifle site. Modeling results show higher lignin content in the NRZ sediments and greater Fe

  18. Controls on silicon cycling in Southeast Asian rice production systems

    NASA Astrophysics Data System (ADS)

    Klotzbücher, Thimo; Marxen, Anika; Vetterlein, Doris; Jahn, Reinhold

    2013-04-01

    Recent research suggests that silicon (Si) is beneficial for rice plants, i.e., a sufficient Si supply improves their resistance against pests and pathogens and increases the uptake of essential nutrients. Despite its potential importance for rice yields, cycling of Si in rice production systems is poorly studied. We assess plant-available Si (Sipa; determined using acetate extraction) in topsoils (Ap+Arp horizons) and Si uptake by plants at 70 paddy fields managed by local farmers in contrasting regions of Vietnam and the Philippines. First results show that Sipa contents are considerably larger in Philippine (217 ± 100 mg Sipa kg-1 ) than in Vietnamese (32 ± 19 mg Sipa kg-1) paddy soils. Rice straw from the Philippines contains 8.6 ± 0.9 % Si, straw from Vietnam 5.0 ± 1.2 % Si. Laboratory experiments showed that Si is limiting the growth of rice plants in some of the Vietnamese soils. We assume that differences in geo-/ pedologic conditions between Vietnam and the Philippines explain the data. Large Sipa contents in the Philippine soils are due to recent rock formation by active volcanism, hence, by a large Sipa input due to mineral weathering in recent geologic history. In contrast, parent materials of the Vietnamese paddy soils derive from old and highly weathered land surfaces. Hence, our data suggest that geo-/pedologic conditions are the main control for the availability of Si in paddy soils. Currently, we examine the relevance of agricultural practices for small-scale differences in the availability of Si within regions. Inadequate practices, such as removal of rice straw from the fields, might deplete Sipa in paddy soils causing a decrease in rice yields in some regions of Vietnam. We investigate the role of phytoliths (amorphous Si bodies contained in rice straw) as source of Sipa in paddy soils. Our methods include laboratory experiments and the assessment of turnover times of phytoliths in paddy soils; first results will be presented and discussed

  19. The cortical control of cycling exercise in stroke patients: an fNIRS study.

    PubMed

    Lin, Pei-Yi; Chen, Jia-Jin Jason; Lin, Sang-I

    2013-10-01

    Stroke survivors suffering from deficits in motor control typically have limited functional abilities, which could result in poor quality of life. Cycling exercise is a common training paradigm for restoring locomotion rhythm in patients. The provision of speed feedback has been used to facilitate the learning of controlled cycling performance and the neuromuscular control of the affected leg. However, the central mechanism for motor relearning of active and passive pedaling motions in stroke patients has not been investigated as extensively. The aim of this study was to measure the cortical activation patterns during active cycling with and without speed feedback and during power-assisted (passive) cycling in stroke patients. A frequency-domain near-infrared spectroscopy (FD-NIRS) system was used to detect the hemodynamic changes resulting from neuronal activity during the pedaling exercise from the bilateral sensorimotor cortices (SMCs), supplementary motor areas (SMAs), and premotor cortices (PMCs). The variation in cycling speed and the level of symmetry of muscle activation of bilateral rectus femoris were used to evaluate cycling performance. The results showed that passive cycling had a similar cortical activation pattern to that observed during active cycling without feedback but with a smaller intensity of the SMC of the unaffected hemisphere. Enhanced PMC activation of the unaffected side with improved cycling performance was observed during active cycling with feedback, with respect to that observed without feedback. This suggests that the speed feedback enhanced the PMC activation and improved cycling performance in stroke patients.

  20. Evaluation of absorption cycle for space station environmental control system application

    NASA Technical Reports Server (NTRS)

    Sims, W. H.; Oneill, M. J.; Reid, H. C.; Bisenius, P. M.

    1972-01-01

    The study to evaluate an absorption cycle refrigeration system to provide environmental control for the space stations is reported. A zero-gravity liquid/vapor separator was designed and tested. The results were used to design a light-weight, efficient generator for the absorption refrigeration system. It is concluded that absorption cycle refrigeration is feasible for providing space station environmental control.

  1. Effects of the Menstrual Cycle and Oral Contraception on Singers' Pitch Control

    ERIC Educational Resources Information Center

    La, Filipa M. B.; Sundberg, Johan; Howard, David M.; Sa-Couto, Pedro; Freitas, Adelaide

    2012-01-01

    Purpose: Difficulties with intonation and vibrato control during the menstrual cycle have been reported by singers; however, this phenomenon has not yet been systematically investigated. Method: A double-blind randomized placebo-controlled trial assessing effects of the menstrual cycle and use of a combined oral contraceptive pill (OCP) on pitch…

  2. Effects of the Menstrual Cycle and Oral Contraception on Singers' Pitch Control

    ERIC Educational Resources Information Center

    La, Filipa M. B.; Sundberg, Johan; Howard, David M.; Sa-Couto, Pedro; Freitas, Adelaide

    2012-01-01

    Purpose: Difficulties with intonation and vibrato control during the menstrual cycle have been reported by singers; however, this phenomenon has not yet been systematically investigated. Method: A double-blind randomized placebo-controlled trial assessing effects of the menstrual cycle and use of a combined oral contraceptive pill (OCP) on pitch…

  3. METHOD AND APPARATUS FOR CONTROLLING DIRECT-CYCLE NEUTRONIC REACTORS

    DOEpatents

    Reed, G.A.

    1961-01-10

    A control arrangement is offered for a boiling-water reactor. Boric acid is maintained in the water in the reactor and the amount in the reactor is controlled by continuously removing a portion of the water from the reactor, concentrating the boric acid by evaporating the water therefrom, returning a controlled amount of the acid to the reactor, and simultaneously controlling the water level by varying the rate of spent steam return to the reactor.

  4. Muscle contractile function and neural control after repetitive endurance cycling.

    PubMed

    Ross, Emma Z; Gregson, Warren; Williams, Karen; Robertson, Colin; George, Keith

    2010-01-01

    To examine alterations in muscle contractile properties, cortical excitability, and voluntary activation as a consequence of 20 d of repetitive endurance cycling within a 22-d period. Eight well-trained male cyclists completed 20 prolonged cycling stages interspersed by two rest days (days 9 and 17), which replicated the 2007 Tour de France route and schedule. Isometric knee extensor torque and EMG responses of the vastus lateralis in response to percutaneous electrical stimulation and transcranial magnetic stimulation were measured before, on days 9 and 17, and 2 d after completion of Tour de France. Postexercise measurements on days 9 and 17 were taken >18 h after cessation of the previous exercise bout. Maximal voluntary contraction of the knee extensors decreased by 20 +/- 10% (P < 0.01) during Tour de France but recovered after 2 d of rest. Peripherally evoked M-wave and potentiated twitch responses were also significantly decreased during Tour de France, up to 31 +/- 21% and 22 +/- 18%, respectively (P < 0.05), but returned to baseline values after 2 d of recovery. Voluntary activation was reduced to 75 +/- 8% (P < 0.05) during Tour de France and remained significantly depressed (79 +/- 7%, P < 0.05) after completion. The amplitude of motor evoked potentials was decreased by 44 +/- 28% (P < 0.01) on day 9 and remained significantly depressed during the remainder of, and after, Tour de France. A reduction in knee extensor strength, which occurs after repetitive prolonged cycling exercise, is a result of both central and peripheral processes. Reduced sarcolemmal excitability and impairment of contractile mechanisms exists even after 18 h of recovery. An enduring reduction in corticomotor output persists even after 2 d of rest.

  5. Interacting factors in the control of the crustacean molt cycle

    SciTech Connect

    Skinner, D.M.

    1985-01-01

    In order to account for the known phenomena of the crustacean molt cycle, at least six factors must be postulated: a molting hormone (20-OH-ecdysone), a molt-inhibiting hormone (MIH), an anecdysial limb autotomy factor, a proecdysial limb-autotomy factor, a limb growth-inhibiting factor and an exuviation factor. Only the molting hormone and its derivatives have been chemically well defined. The various factors interact in complex ways to maintain not only a coordinated proecdysial period in preparation for exuviation but also a proecdysial period with the flexibility to respond to such interim hazards as the loss of partially regenerated limbs. 79 references, 2 figures, 1 table.

  6. Interacting factors in the control of the crustacean molt cycle

    SciTech Connect

    Skinner, D.M.

    1983-01-01

    In order to account for the known phenomena of the crustacean molt cycle, at least six factors must be postulated: a molting hormone (20-OH-ecdysone), a molt inhibiting hormone (MIH), an anecdysial limb autotomy factor, a proecdysial limb autotomy factor, a limb growth inhibiting factor and an exuviation factor. Only the molting hormone and its derivatives have been chemically well defined. The various factors interact in complex ways to maintain not only a coordinated proecdysial period in preparation for exuviation but also a proecdysial period with the flexibility to respond to such interim hazards as the loss of partially regenerated limbs. 78 references, 2 figures, 1 table.

  7. Non-MTC gait cycles: An adaptive toe trajectory control strategy in older adults.

    PubMed

    Santhiranayagam, Braveena K; Sparrow, W A; Lai, Daniel T H; Begg, Rezaul K

    2017-03-01

    Minimum-toe-clearance (MTC) above the walking surface is a critical representation of toe-trajectory control due to its association with tripping risk. Not all gait cycles exhibit a clearly defined MTC within the swing phase but there have been few previous accounts of the biomechanical characteristics of non-MTC gait cycles. The present report investigated the within-subject non-MTC gait cycle characteristics of 15 older adults (mean 73.1 years) and 15 young controls (mean 26.1 years). Participants performed the following tasks on a motorized treadmill: preferred speed walking, dual task walking (carrying a glass of water) and a dual-task speed-matched control. Toe position-time coordinates were acquired using a 3 dimensional motion capture system. When MTC was present, toe height at MTC (MTCheight) was extracted. The proportion of non-MTC gait cycles was computed for the age groups and individuals. For non-MTC gait cycles an 'indicative' toe height at the individual's average swing phase time (MTCtime) for observed MTC cycles was averaged across multiple non-MTC gait cycles. In preferred-speed walking Young demonstrated 2.9% non-MTC gait cycles and Older 18.7%. In constrained walking conditions both groups increased non-MTC gait cycles and some older adults revealed over 90%, confirming non-MTC gait cycles as an ageing-related phenomenon in lower limb trajectory control. For all participants median indicative toe-height on non-MTC gait cycles was greater than median MTCheight. This result suggests that eliminating the biomechanically hazardous MTC event by adopting more of the higher-clearance non-MTC gait cycles, is adaptive in reducing the likelihood of toe-ground contact. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Control of sleep by a network of cell cycle genes.

    PubMed

    Afonso, Dinis J S; Machado, Daniel R; Koh, Kyunghee

    2015-01-01

    Sleep is essential for health and cognition, but the molecular and neural mechanisms of sleep regulation are not well understood. We recently reported the identification of TARANIS (TARA) as a sleep-promoting factor that acts in a previously unknown arousal center in Drosophila. tara mutants exhibit a dose-dependent reduction in sleep amount of up to ∼60%. TARA and its mammalian homologs, the Trip-Br (Transcriptional Regulators Interacting with PHD zinc fingers and/or Bromodomains) family of proteins, are primarily known as transcriptional coregulators involved in cell cycle progression, and contain a conserved Cyclin-A (CycA) binding homology domain. We found that tara and CycA synergistically promote sleep, and CycA levels are reduced in tara mutants. Additional data demonstrated that Cyclin-dependent kinase 1 (Cdk1) antagonizes tara and CycA to promote wakefulness. Moreover, we identified a subset of CycA expressing neurons in the pars lateralis, a brain region proposed to be analogous to the mammalian hypothalamus, as an arousal center. In this Extra View article, we report further characterization of tara mutants and provide an extended discussion of our findings and future directions within the framework of a working model, in which a network of cell cycle genes, tara, CycA, and Cdk1, interact in an arousal center to regulate sleep.

  9. Control of sleep by a network of cell cycle genes

    PubMed Central

    Afonso, Dinis J. S.; Machado, Daniel R.; Koh, Kyunghee

    2015-01-01

    ABSTRACT Sleep is essential for health and cognition, but the molecular and neural mechanisms of sleep regulation are not well understood. We recently reported the identification of TARANIS (TARA) as a sleep-promoting factor that acts in a previously unknown arousal center in Drosophila. tara mutants exhibit a dose-dependent reduction in sleep amount of up to ∼60%. TARA and its mammalian homologs, the Trip-Br (Transcriptional Regulators Interacting with PHD zinc fingers and/or Bromodomains) family of proteins, are primarily known as transcriptional coregulators involved in cell cycle progression, and contain a conserved Cyclin-A (CycA) binding homology domain. We found that tara and CycA synergistically promote sleep, and CycA levels are reduced in tara mutants. Additional data demonstrated that Cyclin-dependent kinase 1 (Cdk1) antagonizes tara and CycA to promote wakefulness. Moreover, we identified a subset of CycA expressing neurons in the pars lateralis, a brain region proposed to be analogous to the mammalian hypothalamus, as an arousal center. In this Extra View article, we report further characterization of tara mutants and provide an extended discussion of our findings and future directions within the framework of a working model, in which a network of cell cycle genes, tara, CycA, and Cdk1, interact in an arousal center to regulate sleep. PMID:26925838

  10. Positive feedback between PU.1 and the cell cycle controls myeloid differentiation.

    PubMed

    Kueh, Hao Yuan; Champhekar, Ameya; Champhekhar, Ameya; Nutt, Stephen L; Elowitz, Michael B; Rothenberg, Ellen V

    2013-08-09

    Regulatory gene circuits with positive-feedback loops control stem cell differentiation, but several mechanisms can contribute to positive feedback. Here, we dissect feedback mechanisms through which the transcription factor PU.1 controls lymphoid and myeloid differentiation. Quantitative live-cell imaging revealed that developing B cells decrease PU.1 levels by reducing PU.1 transcription, whereas developing macrophages increase PU.1 levels by lengthening their cell cycles, which causes stable PU.1 accumulation. Exogenous PU.1 expression in progenitors increases endogenous PU.1 levels by inducing cell cycle lengthening, implying positive feedback between a regulatory factor and the cell cycle. Mathematical modeling showed that this cell cycle-coupled feedback architecture effectively stabilizes a slow-dividing differentiated state. These results show that cell cycle duration functions as an integral part of a positive autoregulatory circuit to control cell fate.

  11. [Integrins and cell cycle control by the environment].

    PubMed

    Bernard, A; Bernard, G

    2000-04-01

    Integrins insure cell adhesion to extra-cellular matrix components; they are thus involved in tissue architecture. They also can insure intercellular adhesions by binding to surface molecules from the immunoglobulin superfamily. Integrins binding to their ligands induce cytoskeleton reorganisation and, consequently, they gather into focal adhesion contacts. This greatly strenghthens mechanical forces. Nevertheless, integrins can also participate in cell locomotion and, moreover, tranduce within cells signals that can extensively influence cell metabolism, cell cycle and apoptosis. Doing so, they can interact with signals from other cellular receptors, such as soluble growth factors. They are therefore key molecules to integrate intrinsic and extrinsic events of the cellular behavior. They profoundly influence oncogenesis and the metastatic process.

  12. Cycle control and side effects of a new combiphasic oral contraceptive regimen.

    PubMed

    Dieben, T O; op ten Berg, M T; Coelingh Bennink, H J

    1994-07-01

    In a multicentre study 882 women were treated during a total of 12,850 cycles with a new combiphasic contraceptive: CTR 24. The study period was 18 cycles. The combiphasic preparation CTR 24 contains 25 micrograms desogestrel (CAS 54024-22-5) plus 40 micrograms ethinylestradiol (CAS 57-63-6) daily for the first 7 days followed by the combination of 125 micrograms desogestrel and 30 micrograms ethinyl-estradiol daily for the subsequent 15 days. The bleeding patterns were analysed over pill cycles and a comparison was made between starters and switchers. The cycle control of the combination was very good. The side effect profile was favourable.

  13. SON controls cell-cycle progression by coordinated regulation of RNA splicing.

    PubMed

    Ahn, Eun-Young; DeKelver, Russell C; Lo, Miao-Chia; Nguyen, Tuyet Ann; Matsuura, Shinobu; Boyapati, Anita; Pandit, Shatakshi; Fu, Xiang-Dong; Zhang, Dong-Er

    2011-04-22

    It has been suspected that cell-cycle progression might be functionally coupled with RNA processing. However, little is known about the role of the precise splicing control in cell-cycle progression. Here, we report that SON, a large Ser/Arg (SR)-related protein, is a splicing cofactor contributing to efficient splicing of cell-cycle regulators. Downregulation of SON leads to severe impairment of spindle pole separation, microtubule dynamics, and genome integrity. These molecular defects result from inadequate RNA splicing of a specific set of cell-cycle-related genes that possess weak splice sites. Furthermore, we show that SON facilitates the interaction of SR proteins with RNA polymerase II and other key spliceosome components, suggesting its function in efficient cotranscriptional RNA processing. These results reveal a mechanism for controlling cell-cycle progression through SON-dependent constitutive splicing at suboptimal splice sites, with strong implications for its role in cancer and other human diseases.

  14. 78 FR 71532 - Amendments to Material Control and Accounting Regulations and Proposed Guidance for Fuel Cycle...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-29

    ... Control and Accounting Regulations and Proposed Guidance for Fuel Cycle Facility Material Control and Accounting Plans and Completing the U.S. Nuclear Regulatory Commission Form 327 AGENCY: Nuclear Regulatory... regulations for material control and accounting (MC&A) of special nuclear material (SNM) and the proposed...

  15. Limit-cycle-based control of the myogenic wingbeat rhythm in the fruit fly Drosophila

    PubMed Central

    Bartussek, Jan; Mutlu, A. Kadir; Zapotocky, Martin; Fry, Steven N.

    2013-01-01

    In many animals, rhythmic motor activity is governed by neural limit cycle oscillations under the control of sensory feedback. In the fruit fly Drosophila melanogaster, the wingbeat rhythm is generated myogenically by stretch-activated muscles and hence independently from direct neural input. In this study, we explored if generation and cycle-by-cycle control of Drosophila's wingbeat are functionally separated, or if the steering muscles instead couple into the myogenic rhythm as a weak forcing of a limit cycle oscillator. We behaviourally tested tethered flying flies for characteristic properties of limit cycle oscillators. To this end, we mechanically stimulated the fly's ‘gyroscopic’ organs, the halteres, and determined the phase relationship between the wing motion and stimulus. The flies synchronized with the stimulus for specific ranges of stimulus amplitude and frequency, revealing the characteristic Arnol'd tongues of a forced limit cycle oscillator. Rapid periodic modulation of the wingbeat frequency prior to locking demonstrates the involvement of the fast steering muscles in the observed control of the wingbeat frequency. We propose that the mechanical forcing of a myogenic limit cycle oscillator permits flies to avoid the comparatively slow control based on a neural central pattern generator. PMID:23282849

  16. Reactivity-controlled compression ignition drive cycle emissions and fuel economy estimations using vehicle system simulations

    DOE PAGES

    Curran, Scott J.; Gao, Zhiming; Wagner, Robert M.

    2014-12-22

    In-cylinder blending of gasoline and diesel to achieve reactivity-controlled compression ignition has been shown to reduce NOX and soot emissions while maintaining or improving brake thermal efficiency as compared with conventional diesel combustion. The reactivity-controlled compression ignition concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load, allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. In this paper, a multi-mode reactivity-controlled compression ignition strategy is employed where the engine switches from reactivity-controlled compression ignition to conventional diesel combustion whenmore » speed and load demand are outside of the experimentally determined reactivity-controlled compression ignition range. The potential for reactivity-controlled compression ignition to reduce drive cycle fuel economy and emissions is not clearly understood and is explored here by simulating the fuel economy and emissions for a multi-mode reactivity-controlled compression ignition–enabled vehicle operating over a variety of US drive cycles using experimental engine maps for multi-mode reactivity-controlled compression ignition, conventional diesel combustion, and a 2009 port-fuel injected gasoline engine. Drive cycle simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission. Multi-mode reactivity-controlled compression ignition fuel economy simulation results are compared with the same vehicle powered by a representative 2009 port-fuel injected gasoline engine over multiple drive cycles. Finally, engine-out drive cycle emissions are compared with conventional diesel combustion, and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.« less

  17. Reactivity-controlled compression ignition drive cycle emissions and fuel economy estimations using vehicle system simulations

    SciTech Connect

    Curran, Scott J.; Gao, Zhiming; Wagner, Robert M.

    2014-12-22

    In-cylinder blending of gasoline and diesel to achieve reactivity-controlled compression ignition has been shown to reduce NOX and soot emissions while maintaining or improving brake thermal efficiency as compared with conventional diesel combustion. The reactivity-controlled compression ignition concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load, allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. In this paper, a multi-mode reactivity-controlled compression ignition strategy is employed where the engine switches from reactivity-controlled compression ignition to conventional diesel combustion when speed and load demand are outside of the experimentally determined reactivity-controlled compression ignition range. The potential for reactivity-controlled compression ignition to reduce drive cycle fuel economy and emissions is not clearly understood and is explored here by simulating the fuel economy and emissions for a multi-mode reactivity-controlled compression ignition–enabled vehicle operating over a variety of US drive cycles using experimental engine maps for multi-mode reactivity-controlled compression ignition, conventional diesel combustion, and a 2009 port-fuel injected gasoline engine. Drive cycle simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission. Multi-mode reactivity-controlled compression ignition fuel economy simulation results are compared with the same vehicle powered by a representative 2009 port-fuel injected gasoline engine over multiple drive cycles. Finally, engine-out drive cycle emissions are compared with conventional diesel combustion, and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.

  18. Control system development for an organic Rankine cycle engine

    NASA Technical Reports Server (NTRS)

    Bergthold, F. M., Jr.; Fulton, D. G.; Haskins, H. J.

    1981-01-01

    The development of a control logic to govern the toluene throttle valve and verify the stability of the speed control approach for multiple engines connected to a 1 MWe point focus solar generator installation for distributed applications is presented. The toluene is is pumped by booster and main feed pumps through a regenerator to the parabolic focus receiver, with the flow rate controlled by a valve to remain at critical level of 4.1 MPa. The valve changes the inlet pressure at the turbine nozzle block. Each concentrator would produce 76 kWth and 20 kWe. Dynamic variables in the logic account for insolation variation, fluid temperature, ac grid voltage, the thermal dynamics of the regenerator, and variations in the head supplied by the feed pump. Separate analyses are presented for the turbine shaft speed and toluene loop dynamics. The resulting logic is considered preliminary and suitable only in full insolation conditions. Extension of the model to nonlinear perturbations is indicated.

  19. [Development of open cycling air pressure control system used for glaucoma research].

    PubMed

    Zhang, Hong; Li, Gui-gang; Wang, Xue-fang; Hu, Wei-kun; Xie, Er-juan; Chen, Lian-yi; Shan, Chang-mei; Zhao, Guo-hong

    2006-06-01

    To develop and set up a new culture system, which can apply pressure to cultured cells with open cycling air. The effects of this new system on the pH value, HCO(3)(-) concentration, O(2) pressure (pO(2)), CO2 pressure (pCO(2)) and the proliferation of retinal pigment epithelium (RPE) were tested to evaluate its efficiency in the study of glaucoma. In the open cycling air pressure control culture system, the pressure inside the culture flasks was controlled by increase or decrease of the perfuse airflow. The influence of different culture systems (normal pressure culture system, open cycling air pressure control system and occlusive pressure control system) on the pH value, HCO(3)(-) concentration, pO(2), pCO(2) and proliferation of RPE were tested. The data were analyzed with SPSS software. The open cycling air pressure control culture system worked effectively, the pressure inside the culture flask can be controlled from 0 to 100 mm Hg. The difference of pH value, HCO(3)(-) concentration, pO(2), and pCO(2) of culture medium and the proliferation of RPE between normal pressure culture system and open cycling air pressure control system were not significant (P = 0.927, 0.887, 0.818, 0.770, 0.719, respectively). There was significant difference in these data between normal pressure culture system and occlusive pressure control system (P = 0.001, 0.000, 0.000, 0.000, 0.000, respectively). A new designed standard culture system applying pressure to cells with open cycling air was effective at pressure controlling and pH value, HCO(3)(-) concentration, pO(2) and pCO(2) controlling. This system may act as an ideal model in the experimental study of glaucoma.

  20. ASDTIC duty-cycle control for power converters.

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Schoenfeld, A. D.

    1972-01-01

    The application of analog signal to discrete interval converter (ASDTIC), a hybrid micromodule, two-loop control subsystem, to a switching, stepdown dc-to-dc converter is described. The power circuitry, interface and ASDTIC subsystems used in this switching regulator were developed to exhibit the improved regulation, transient performance, regulator stability, and freedom from the effects of variations in parts characteristics due to environmental changes and aging. The circuitry and performance characteristics of a +10-V dc switching converter as well as that of the ASDTIC micromodule are described. Realization of the ASDTIC hybrid micromodule has been accomplished with hermetically sealed, beam-lead, bonded/deposited nichrome thin film resistors, discrete capacitors, and integrated circuits on dilithic, glazed alumina substrates, using 22 feed through terminals in an integrated package.

  1. Initial Viscosity Controls on Thermal Evolution and Water Cycling

    NASA Astrophysics Data System (ADS)

    Chotalia, K.; Cagney, N.; Lithgow-Bertelloni, C. R.; Brodholt, J. P.

    2016-12-01

    Parametrised models provide great insight into the thermal and rheological evolution of a cooling planet. They have previously been used to investigate the effects of a water-dependent rheology, a layered convective model and viscous dissipation. However, most models fail to look at the effects of initial conditions, particularly viscosity which is a function of grainsize and water concentration. We present models to investigate the effects of initial viscosity in both parametrised and Cartesian models to highlight the role of viscosity in planetary evolution. The model is based on Crowley et al. (2011), which solves for the conservation of mass and energy across a surface ocean and mantle. Using a variable order numerical differentiation formulae solver, mantle temperature and water concentration of both the mantle and surface ocean are determined. Further investigation will show the dynamics in 2D with a thermal evolution similar to those seen in the parametrised model and comparisons to a thermodynamic depth-dependent code based on mixing length theory. Preliminary results show that initial viscosity controls the dynamics of the convecting system where water does not influence viscosity. When the initial viscosity is high, the system is too stiff to convect and undergoes a period of heating until viscosity is low enough to allow the mantle to cool. A low initial viscosity enables a high surface heat flow and the mantle experiences a period of rapid cooling. These two distinct regimes control the exchange of water between the mantle and surface reservoirs, either catastrophically releasing water during initial cooling or stalling the release of water until convection occurs after initial heating. This ongoing work reveals that the initial viscosity is crucial for understanding the complex feedback between volatiles and planetary evolution.

  2. Circadian control of the sleep-wake cycle.

    PubMed

    Beersma, Domien G M; Gordijn, Marijke C M

    2007-02-28

    It is beyond doubt that the timing of sleep is under control of the circadian pacemaker. Humans are a diurnal species; they sleep mostly at night, and they do so at approximately 24-h intervals. If they do not adhere to this general pattern, for instance when working night shifts or when travelling across time zones, they experience the stubborn influence of their circadian clock. In recent years much has been discovered about the organisation of the circadian clock. New photoreceptor cells in the retina have been found to influence the input to the clock, and much of the molecular machinery of the clock has been unravelled. It is now known that the circadian rhythm of sleep and wakefulness is only loosely coupled to the circadian rhythm of the pacemaker. New theories have been proposed for the functions of sleep and the sites at which those functions are executed. In spite of this rapid increase in knowledge of the circadian clock and of sleep regulatory processes, much remains to be discovered concerning the precise interaction between the biological clock and sleep timing. This is particularly unfortunate in view of the 24-h demands of our society for 7 days a week. Too little is known about the negative consequences of the societal pressures on well-being and performance.

  3. Cell-cycle control of gene expression in budding and fission yeast.

    PubMed

    Bähler, Jürg

    2005-01-01

    Cell-cycle control of transcription seems to be a universal feature of proliferating cells, although relatively little is known about its biological significance and conservation between organisms. The two distantly related yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe have provided valuable complementary insight into the regulation of periodic transcription as a function of the cell cycle. More recently, genome-wide studies of proliferating cells have identified hundreds of periodically expressed genes and underlying mechanisms of transcriptional control. This review discusses the regulation of three major transcriptional waves, which roughly coincide with three main cell-cycle transitions (initiation of DNA replication, entry into mitosis, and exit from mitosis). I also compare and contrast the transcriptional regulatory networks between the two yeasts and discuss the evolutionary conservation and possible roles for cell cycle-regulated transcription.

  4. Cell-Cycle Control of Bivalent Epigenetic Domains Regulates the Exit from Pluripotency.

    PubMed

    Singh, Amar M; Sun, Yuhua; Li, Li; Zhang, Wenjuan; Wu, Tianming; Zhao, Shaying; Qin, Zhaohui; Dalton, Stephen

    2015-09-08

    Here we show that bivalent domains and chromosome architecture for bivalent genes are dynamically regulated during the cell cycle in human pluripotent cells. Central to this is the transient increase in H3K4-trimethylation at developmental genes during G1, thereby creating a "window of opportunity" for cell-fate specification. This mechanism is controlled by CDK2-dependent phosphorylation of the MLL2 (KMT2B) histone methyl-transferase, which facilitates its recruitment to developmental genes in G1. MLL2 binding is required for changes in chromosome architecture around developmental genes and establishes promoter-enhancer looping interactions in a cell-cycle-dependent manner. These cell-cycle-regulated loops are shown to be essential for activation of bivalent genes and pluripotency exit. These findings demonstrate that bivalent domains are established to control the cell-cycle-dependent activation of developmental genes so that differentiation initiates from the G1 phase.

  5. Division of labour between Myc and G1 cyclins in cell cycle commitment and pace control.

    PubMed

    Dong, Peng; Maddali, Manoj V; Srimani, Jaydeep K; Thélot, François; Nevins, Joseph R; Mathey-Prevot, Bernard; You, Lingchong

    2014-09-01

    A body of evidence has shown that the control of E2F transcription factor activity is critical for determining cell cycle entry and cell proliferation. However, an understanding of the precise determinants of this control, including the role of other cell-cycle regulatory activities, has not been clearly defined. Here, recognizing that the contributions of individual regulatory components could be masked by heterogeneity in populations of cells, we model the potential roles of individual components together with the use of an integrated system to follow E2F dynamics at the single-cell level and in real time. These analyses reveal that crossing a threshold amplitude of E2F accumulation determines cell cycle commitment. Importantly, we find that Myc is critical in modulating the amplitude, whereas cyclin D/E activities have little effect on amplitude but do contribute to the modulation of duration of E2F activation, thereby affecting the pace of cell cycle progression.

  6. A ubiquitous wearable unit for controlling muscular fatigue during cycling exercise sessions.

    PubMed

    Kiryu, Tohru; Yamashita, Kazuki

    2007-01-01

    For health promotion and motor rehabilitation, controlling muscular fatigue on-site is important during exercise sessions. We have developed a ubiquitous wearable unit with a Linux board and tried to apply it to the control of a torque-assisted bicycle with a biosignal-based fuzzy system designed for a cycle ergometer. The results showed that an appropriate design for the cycle ergometor (indoor exercise) would be sufficiently applicable for the torque-assisted bicycle (outdoor exercise) in terms of heart rate, but was not sufficient in terms of muscular fatigue. It needs more detailed control for muscular activity.

  7. Functional electrical stimulation with cycling in the critically ill: a pilot case-matched control study.

    PubMed

    Parry, Selina M; Berney, Sue; Warrillow, Stephen; El-Ansary, Doa; Bryant, Adam L; Hart, Nicholas; Puthucheary, Zudin; Koopman, Renè; Denehy, Linda

    2014-08-01

    The purpose was to determine (a) safety and feasibility of functional electrical stimulation (FES)-cycling and (b) compare FES-cycling to case-matched controls in terms of functional recovery and delirium outcomes. Sixteen adult intensive care unit patients with sepsis ventilated for more than 48 hours and in the intensive care unit for at least 4 days were included. Eight subjects underwent FES-cycling in addition to usual care and were compared to 8 case-matched control individuals. Primary outcomes were safety and feasibility of FES-cycling. Secondary outcomes were Physical Function in Intensive Care Test scored on awakening, time to reach functional milestones, and incidence and duration of delirium. One minor adverse event was recorded. Sixty-nine out of total possible 95 FES sessions (73%) were completed. A visible or palpable contraction was present 80% of the time. There was an improvement in Physical Function in Intensive Care Test score of 3.9/10 points in the intervention cohort with faster recovery of functional milestones. There was also a shorter duration of delirium in the intervention cohort. The delivery of FES-cycling is both safe and feasible. The preliminary findings suggest that FES-cycling may improve function and reduce delirium. Further research is required to confirm the findings of this study and evaluate the efficacy of FES-cycling. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. A cell cycle-controlled redox switch regulates the topoisomerase IV activity

    PubMed Central

    Narayanan, Sharath; Janakiraman, Balaganesh; Kumar, Lokesh

    2015-01-01

    Topoisomerase IV (topo IV), an essential factor during chromosome segregation, resolves the catenated chromosomes at the end of each replication cycle. How the decatenating activity of the topo IV is regulated during the early stages of the chromosome cycle despite being in continuous association with the chromosome remains poorly understood. Here we report a novel cell cycle-regulated protein in Caulobacter crescentus, NstA (negative switch for topo IV decatenation activity), that inhibits the decatenation activity of the topo IV during early stages of the cell cycle. We demonstrate that in C. crescentus, NstA acts by binding to the ParC DNA-binding subunit of topo IV. Most importantly, we uncover a dynamic oscillation of the intracellular redox state during the cell cycle, which correlates with and controls NstA activity. Thus, we propose that predetermined dynamic intracellular redox fluctuations may act as a global regulatory switch to control cellular development and cell cycle progression and may help retain pathogens in a suitable cell cycle state when encountering redox stress from the host immune response. PMID:26063575

  9. Cell cycle control in the early embryonic development of aquatic animal species.

    PubMed

    Siefert, Joseph C; Clowdus, Emily A; Sansam, Christopher L

    2015-12-01

    The cell cycle is integrated with many aspects of embryonic development. Not only is proper control over the pace of cell proliferation important, but also the timing of cell cycle progression is coordinated with transcription, cell migration, and cell differentiation. Due to the ease with which the embryos of aquatic organisms can be observed and manipulated, they have been a popular choice for embryologists throughout history. In the cell cycle field, aquatic organisms have been extremely important because they have played a major role in the discovery and analysis of key regulators of the cell cycle. In particular, the frog Xenopus laevis has been instrumental for understanding how the basic embryonic cell cycle is regulated. More recently, the zebrafish has been used to understand how the cell cycle is remodeled during vertebrate development and how it is regulated during morphogenesis. This review describes how some of the unique strengths of aquatic species have been leveraged for cell cycle research and suggests how species such as Xenopus and zebrafish will continue to reveal the roles of the cell cycle in human biology and disease.

  10. External factors controlling annual testosterone and thyroxine cycles in the edible dormouse Glis glis.

    PubMed

    Jallageas, M; Assenmacher, I

    1984-01-01

    Annual patterns of hibernation, body weight, plasma testosterone and thyroxine were measured in two groups of edible dormice exposed to a constant photoperiod and to either environmental temperature (I), the four functions displayed annual cycles and the two hormonal cycles were parallel and restricted to the aroused state, while in group II only irregular infradian fluctuations were observed. However, a body temperature of 30 degrees C remained the critical lower limit enabling the start of the testosterone cycles for the two groups. Respective roles of endogenous and synchronizing mechanisms in controlling biological rhythms are discussed.

  11. Chopper-controlled discharge life cycling studies on lead-acid batteries

    NASA Technical Reports Server (NTRS)

    Kraml, J. J.; Ames, E. P.

    1982-01-01

    State-of-the-art 6 volt lead-acid golf car batteries were tested. A daily charge/discharge cycling to failure points under various chopper controlled pulsed dc and continuous current load conditions was undertaken. The cycle life and failure modes were investigated for depth of discharge, average current chopper frequency, and chopper duty cycle. It is shown that battery life is primarily and inversely related to depth of discharge and discharge current. Failure mode is characterized by a gradual capacity loss with consistent evidence of cell element aging.

  12. 78 FR 67223 - Proposed Guidance for Fuel Cycle Facility; Material Control and Accounting Plans and Completing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-08

    ... for Fuel Cycle Facility; Material Control and Accounting Plans and Completing NRC Form 327 and Amendments to Material Control and Accounting Regulations; Proposed Rules #0;#0;Federal Register / Vol. 78... and Accounting Plans and Completing NRC Form 327 AGENCY: Nuclear Regulatory Commission. ACTION: Draft...

  13. Unifying the Gait Cycle in the Control of a Powered Prosthetic Leg

    PubMed Central

    Martin, Anne E.; Gregg, Robert D.

    2015-01-01

    This paper presents a novel control strategy for an above-knee powered prosthetic leg that unifies the entire gait cycle, eliminating the need to switch between controllers during different periods of gait. Current control methods divide the gait cycle into several sequential periods each with independent controllers, resulting in many patient-specific control parameters and switching rules that must be tuned by clinicians. Having a single controller could reduce the number of control parameters to be tuned for each patient, thereby reducing the clinical time and effort involved in fitting a powered prosthesis for a lower-limb amputee. Using the Discrete Fourier Transformation, a single virtual constraint is derived that exactly characterizes the desired actuated joint motion over the entire gait cycle. Because the virtual constraint is defined as a periodic function of a monotonically increasing phase variable, no switching or resetting is necessary within or across gait cycles. The output function is zeroed using feedback linearization to produce a single, unified controller. The method is illustrated with simulations of a powered knee-ankle prosthesis in an amputee biped model and with examples of systematically generated output functions for different walking speeds. PMID:26913092

  14. Input visualization for the Cyclus nuclear fuel cycle simulator: CYClus Input Control

    SciTech Connect

    Flanagan, R.; Schneider, E.

    2013-07-01

    This paper discusses and demonstrates the methods used for the graphical user interface for the Cyclus fuel cycle simulator being developed at the University of Wisconsin-Madison. Cyclus Input Control (CYCIC) is currently being designed with nuclear engineers in mind, but future updates to the program will be made to allow even non-technical users to quickly and efficiently simulate fuel cycles to answer the questions important to them. (authors)

  15. Controls over fungal communities and consequences for nutrient cycling

    NASA Astrophysics Data System (ADS)

    Treseder, K. K.; Majumder, P.; Bent, E.; Borneman, J.; Allison, S. D.; Hanson, C. A.

    2007-12-01

    Soils harbor a high diversity of microbes-- as many as 100 species of fungi within a square meter. If different species target different components of litter, a more diverse community of fungi should lead to faster decomposition rates. We examined the hypotheses that variation in substrate use among fungal groups and variation in nitrogen availability are both important controls over the diversity of fungi in an Alaskan boreal forest. Nitrogen availability was considered because microbes are often N-limited, and because humans are altering N availability via anthropogenic N deposition and global warming. We used nucleotide analogs to link fungal groups with their role in decomposition in field samples. Leaf litter collected from the forest floor was supplemented with one of four N-containing compounds. Bromodeoxyuridine (BrdU, a thymidine analog) was also added. After 48 hours incubation, DNA was extracted. Most growing fungi should have assimilated the BrdU into new DNA. Their genetic identity was determined using oligonucleotide fingerprinting of rRNA genes (OFRG). OFRG is an rRNA gene profiling method that sorts genes into taxonomic groups with a high degree of resolution, and has a large capacity for sample processing. Fungal groups that proliferated following the addition of a given compound probably metabolized that compound. We found that fungal taxa varied in their responses to different substrates, indicating that they differed in substrate use. Specifically, community composition of fungi was significantly different among substrate treatments (P < 0.001). In addition, of the 15 dominant taxa, seven displayed significant preferences for one substrate over another. For instance, taxa within the Helotiales preferred glutamate (P = 0.001); Sporidiales, tannin-protein complexes (P = 0.014); Saccharomycetales, arginine (P = 0.042); and Polyporales, arginine and lignocellulose (P = 0.040). In a complementary experiment, we used BrdU labeling to characterize

  16. Advanced Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2013-01-01

    A dual flow-path inlet system is being tested to evaluate methodologies for a Turbine Based Combined Cycle (TBCC) propulsion system to perform a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the closed loop control system, which utilizes a shock location sensor to improve inlet performance and operability. Even though the shock location feedback has a coarse resolution, the feedback allows for a reduction in steady state error and, in some cases, better performance than with previous proposed pressure ratio based methods. This paper demonstrates the design and benefit with the implementation of a proportional-integral controller, an H-Infinity based controller, and a disturbance observer based controller.

  17. A quantitative model for cyclin-dependent kinase control of the cell cycle: revisited.

    PubMed

    Uhlmann, Frank; Bouchoux, Céline; López-Avilés, Sandra

    2011-12-27

    The eukaryotic cell division cycle encompasses an ordered series of events. Chromosomal DNA is replicated during S phase of the cell cycle before being distributed to daughter cells in mitosis. Both S phase and mitosis in turn consist of an intricately ordered sequence of molecular events. How cell cycle ordering is achieved, to promote healthy cell proliferation and avert insults on genomic integrity, has been a theme of Paul Nurse's research. To explain a key aspect of cell cycle ordering, sequential S phase and mitosis, Stern & Nurse proposed 'A quantitative model for cdc2 control of S phase and mitosis in fission yeast'. In this model, S phase and mitosis are ordered by their dependence on increasing levels of cyclin-dependent kinase (Cdk) activity. Alternative mechanisms for ordering have been proposed that rely on checkpoint controls or on sequential waves of cyclins with distinct substrate specificities. Here, we review these ideas in the light of experimental evidence that has meanwhile accumulated. Quantitative Cdk control emerges as the basis for cell cycle ordering, fine-tuned by cyclin specificity and checkpoints. We propose a molecular explanation for quantitative Cdk control, based on thresholds imposed by Cdk-counteracting phosphatases, and discuss its implications.

  18. A quantitative model for cyclin-dependent kinase control of the cell cycle: revisited

    PubMed Central

    Uhlmann, Frank; Bouchoux, Céline; López-Avilés, Sandra

    2011-01-01

    The eukaryotic cell division cycle encompasses an ordered series of events. Chromosomal DNA is replicated during S phase of the cell cycle before being distributed to daughter cells in mitosis. Both S phase and mitosis in turn consist of an intricately ordered sequence of molecular events. How cell cycle ordering is achieved, to promote healthy cell proliferation and avert insults on genomic integrity, has been a theme of Paul Nurse's research. To explain a key aspect of cell cycle ordering, sequential S phase and mitosis, Stern & Nurse proposed ‘A quantitative model for cdc2 control of S phase and mitosis in fission yeast’. In this model, S phase and mitosis are ordered by their dependence on increasing levels of cyclin-dependent kinase (Cdk) activity. Alternative mechanisms for ordering have been proposed that rely on checkpoint controls or on sequential waves of cyclins with distinct substrate specificities. Here, we review these ideas in the light of experimental evidence that has meanwhile accumulated. Quantitative Cdk control emerges as the basis for cell cycle ordering, fine-tuned by cyclin specificity and checkpoints. We propose a molecular explanation for quantitative Cdk control, based on thresholds imposed by Cdk-counteracting phosphatases, and discuss its implications. PMID:22084384

  19. Limit cycle analysis of active disturbance rejection control system with two nonlinearities.

    PubMed

    Wu, Dan; Chen, Ken

    2014-07-01

    Introduction of nonlinearities to active disturbance rejection control algorithm might have high control efficiency in some situations, but makes the systems with complex nonlinearity. Limit cycle is a typical phenomenon that can be observed in the nonlinear systems, usually causing failure or danger of the systems. This paper approaches the problem of the existence of limit cycles of a second-order fast tool servo system using active disturbance rejection control algorithm with two fal nonlinearities. A frequency domain approach is presented by using describing function technique and transfer function representation to characterize the nonlinear system. The derivations of the describing functions for fal nonlinearities and treatment of two nonlinearities connected in series are given to facilitate the limit cycles analysis. The effects of the parameters of both the nonlinearity and the controller on the limit cycles are presented, indicating that the limit cycles caused by the nonlinearities can be easily suppressed if the parameters are chosen carefully. Simulations in the time domain are performed to assess the prediction accuracy based on the describing function.

  20. Demonstration of active vibration control on a stirling-cycle cryocooler testbed

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce G.; Flynn, Frederick J.; Gaffney, Monique S.; Johnson, Dean L.; Ross, Ronald G., Jr.

    1992-01-01

    SatCon Technology Corporation has demonstrated excellent vibration reduction performance using active control on the JPL Stirling-cycle cryocooler testbed. The authors address the use of classical narrowband feedback control to meet the cryocooler vibration specifications using one cryocooler in a self-cancellation configuration. Similar vibration reduction performance was obtained using a cryocooler back-to-back configuration by actively controlling a reaction mass actuator that was used to mimic the second cooler.

  1. Model predictive control system and method for integrated gasification combined cycle power generation

    SciTech Connect

    Kumar, Aditya; Shi, Ruijie; Kumar, Rajeeva; Dokucu, Mustafa

    2013-04-09

    Control system and method for controlling an integrated gasification combined cycle (IGCC) plant are provided. The system may include a controller coupled to a dynamic model of the plant to process a prediction of plant performance and determine a control strategy for the IGCC plant over a time horizon subject to plant constraints. The control strategy may include control functionality to meet a tracking objective and control functionality to meet an optimization objective. The control strategy may be configured to prioritize the tracking objective over the optimization objective based on a coordinate transformation, such as an orthogonal or quasi-orthogonal projection. A plurality of plant control knobs may be set in accordance with the control strategy to generate a sequence of coordinated multivariable control inputs to meet the tracking objective and the optimization objective subject to the prioritization resulting from the coordinate transformation.

  2. A microbial avenue to cell cycle control in the plant superkingdom.

    PubMed

    Tulin, Frej; Cross, Frederick R

    2014-10-01

    Research in yeast and animals has resulted in a well-supported consensus model for eukaryotic cell cycle control. The fit of this model to early diverging eukaryotes, such as the plant kingdom, remains unclear. Using the green alga Chlamydomonas reinhardtii, we developed an efficient pipeline, incorporating robotics, semiautomated image analysis, and deep sequencing, to molecularly identify >50 genes, mostly conserved in higher plants, specifically required for cell division but not cell growth. Mutated genes include the cyclin-dependent kinases CDKA (resembling yeast and animal Cdk1) and the plant-specific CDKB. The Chlamydomonas cell cycle consists of a long G1 during which cells can grow >10-fold, followed by multiple rapid cycles of DNA replication and segregation. CDKA and CDKB execute nonoverlapping functions: CDKA promotes transition between G1 and entry into the division cycle, while CDKB is essential specifically for spindle formation and nuclear division, but not for DNA replication, once CDKA-dependent initiation has occurred. The anaphase-promoting complex is required for similar steps in the Chlamydomonas cell cycle as in Opisthokonts; however, the spindle assembly checkpoint, which targets the APC in Opisthokonts, appears severely attenuated in Chlamydomonas, based on analysis of mutants affecting microtubule function. This approach allows unbiased integration of the consensus cell cycle control model with innovations specific to the plant lineage.

  3. Duty cycle control in reactive high-power impulse magnetron sputtering of hafnium and niobium

    NASA Astrophysics Data System (ADS)

    Ganesan, R.; Treverrow, B.; Murdoch, B.; Xie, D.; Ross, A. E.; Partridge, J. G.; Falconer, I. S.; McCulloch, D. G.; McKenzie, D. R.; Bilek, M. M. M.

    2016-06-01

    Instabilities in reactive sputtering have technological consequences and have been attributed to the formation of a compound layer on the target surface (‘poisoning’). Here we demonstrate how the duty cycle of high power impulse magnetron sputtering (HiPIMS) can be used to control the surface conditions of Hf and Nb targets. Variations in the time resolved target current characteristics as a function of duty cycle were attributed to gas rarefaction and to the degree of poisoning of the target surface. As the operation transitions from Ar driven sputtering to metal driven sputtering, the secondary electron emission changes and reduces the target current. The target surface transitions smoothly from a poisoned state at low duty cycles to a quasi-metallic state at high duty cycles. Appropriate selection of duty cycle increases the deposition rate, eliminates the need for active regulation of oxygen flow and enables stable reactive deposition of stoichiometric metal oxide films. A model is presented for the reactive HIPIMS process in which the target operates in a partially poisoned mode with different degrees of oxide layer distribution on its surface that depends on the duty cycle. Finally, we show that by tuning the pulse characteristics, the refractive indices of the metal oxides can be controlled without increasing the absorption coefficients, a result important for the fabrication of optical multilayer stacks.

  4. A Microbial Avenue to Cell Cycle Control in the Plant Superkingdom[C][W][OPEN

    PubMed Central

    Tulin, Frej; Cross, Frederick R.

    2014-01-01

    Research in yeast and animals has resulted in a well-supported consensus model for eukaryotic cell cycle control. The fit of this model to early diverging eukaryotes, such as the plant kingdom, remains unclear. Using the green alga Chlamydomonas reinhardtii, we developed an efficient pipeline, incorporating robotics, semiautomated image analysis, and deep sequencing, to molecularly identify >50 genes, mostly conserved in higher plants, specifically required for cell division but not cell growth. Mutated genes include the cyclin-dependent kinases CDKA (resembling yeast and animal Cdk1) and the plant-specific CDKB. The Chlamydomonas cell cycle consists of a long G1 during which cells can grow >10-fold, followed by multiple rapid cycles of DNA replication and segregation. CDKA and CDKB execute nonoverlapping functions: CDKA promotes transition between G1 and entry into the division cycle, while CDKB is essential specifically for spindle formation and nuclear division, but not for DNA replication, once CDKA-dependent initiation has occurred. The anaphase-promoting complex is required for similar steps in the Chlamydomonas cell cycle as in Opisthokonts; however, the spindle assembly checkpoint, which targets the APC in Opisthokonts, appears severely attenuated in Chlamydomonas, based on analysis of mutants affecting microtubule function. This approach allows unbiased integration of the consensus cell cycle control model with innovations specific to the plant lineage. PMID:25336509

  5. [Intrauterine insemination versus programmed intercourse in cycles of controlled ovaric hyperstimulation].

    PubMed

    Barros Delgadillo, Juan Carlos; Martińez Barrios, Evaristo; Moreno Aburto, Christian; Godines Enríquez, Mirna Souraye; Manzur Navarrete, Félix; Sánchez Solís, Víctor; Barroso Villa, Gerardo

    2008-01-01

    Assisted reproduction techniques are used more and more frequently in the treatment of coulples with infertility diagnosis. To analyze the intrauterine insemination (IUI) value in controlled ovarian hyperstimulation cycles (COH). An analytic, comparative, retrospective and longitudinal case-control study was performed. COH with IUI (group I) or with timed intercourse (TI) (group II) cycles from January 1st 2004 to December 31st 2006 were analyzed. Infertile patients aged between 24 and 42 years (group I) and between 23 and 36 years (group II) were included. The following variables were analyzed: Age, type, etiology and duration of infertility, sperm density and motility after capacitation or seminal analysis, number of total and mature follicles, endometrial thickness, gonadotropin type and dosage, insemination or TI cycle day. Pregnant vs non pregnant and pregnancies in both groups were analyzed. Results were analyzed with the STATA 7.0 and SPSS 12.0 programs. 873 COH+I UI cycles in 539 couples and 246 COH+ TI in 138 patients were analyzed the pregnancy rates per cycle were 13.1% and 5.2% for each group respectively. The mean woman's age was of 32.9 +/- 3.5 and 31.8 +/- 2.7 years for groups I and II respectively. There were significant differences in sperm density in both groups. The remaining variables showed no statistical differences. IUI versus TI do not seems to be superior with respect to the pregnancy rates in COH cycles.

  6. Identification and cell cycle control of a novel pilus system in Caulobacter crescentus

    PubMed Central

    Skerker, Jeffrey M.; Shapiro, Lucy

    2000-01-01

    Pilus assembly in Caulobacter crescentus occurs during a short period of the cell cycle and pili are only present at the flagellar pole of the swarmer cell. Here we report a novel assay to visualize pili by light microscopy that led to the purification of Caulobacter pili and the isolation of a cluster of seven genes, including the major pilin subunit gene pilA. This gene cluster encodes a novel group of pilus assembly proteins. We have shown that the pilA promoter is activated late in the cell cycle and that transcription of the pilin subunit plays an important role in the timing of pilus assembly. pilA transcription is regulated by the global two-component response regulator CtrA, which is essential for the expression of multiple cell cycle events, providing a direct link between assembly of the pilus organelle and bacterial cell cycle control. PMID:10880436

  7. Concise Review: Control of Cell Fate Through Cell Cycle and Pluripotency Networks.

    PubMed

    Boward, Ben; Wu, Tianming; Dalton, Stephen

    2016-06-01

    Pluripotent stem cells (PSCs) proliferate rapidly with a characteristic cell cycle structure consisting of short G1- and G2-gap phases. This applies broadly to PSCs of peri-implantation stage embryos, cultures of embryonic stem cells, induced pluripotent stem cells, and embryonal carcinoma cells. During the early stages of PSC differentiation however, cell division times increase as a consequence of cell cycle remodeling. Most notably, this is indicated by elongation of the G1-phase. Observations linking changes in the cell cycle with exit from pluripotency have raised questions about the role of cell cycle control in maintenance of the pluripotent state. Until recently however, this has been a difficult question to address because of limitations associated with experimental tools. Recent studies now show that pluripotency and cell cycle regulatory networks are intertwined and that cell cycle control mechanisms are an integral, mechanistic part of the PSC state. Studies in embryonal carcinoma, some 30 years ago, first suggested that pluripotent cells initiate differentiation when in the G1-phase. More recently, a molecular "priming" mechanism has been proposed to explain these observations in human embryonic stem cells. Complexity in this area has been increased by the realization that pluripotent cells exist in multiple developmental states and that in addition to each having their own characteristic gene expression and epigenetic signatures, they potentially have alternate modes of cell cycle regulation. This review will summarize current knowledge in these areas and will highlight important aspects of interconnections between the cell cycle, self-renewal, pluripotency, and cell fate decisions. Stem Cells 2016;34:1427-1436. © 2016 AlphaMed Press.

  8. From Hopf Bifurcation to Limit Cycles Control in Underactuated Mechanical Systems

    NASA Astrophysics Data System (ADS)

    Khraief Haddad, Nahla; Belghith, Safya; Gritli, Hassène; Chemori, Ahmed

    2017-06-01

    This paper deals with the problem of obtaining stable and robust oscillations of underactuated mechanical systems. It is concerned with the Hopf bifurcation analysis of a Controlled Inertia Wheel Inverted Pendulum (C-IWIP). Firstly, the stabilization was achieved with a control law based on the Interconnection, Damping, Assignment Passive Based Control method (IDA-PBC). Interestingly, the considered closed-loop system exhibits both supercritical and subcritical Hopf bifurcation for certain gains of the control law. Secondly, we used the center manifold theorem and the normal form technique to study the stability and instability of limit cycles emerging from the Hopf bifurcation. Finally, numerical simulations were conducted to validate the analytical results in order to prove that with IDA-PBC we can control not only the unstable equilibrium but also some trajectories such as limit cycles.

  9. Topology and Control of the Cell-Cycle-Regulated Transcriptional Circuitry

    PubMed Central

    Haase, Steven B.; Wittenberg, Curt

    2014-01-01

    Nearly 20% of the budding yeast genome is transcribed periodically during the cell division cycle. The precise temporal execution of this large transcriptional program is controlled by a large interacting network of transcriptional regulators, kinases, and ubiquitin ligases. Historically, this network has been viewed as a collection of four coregulated gene clusters that are associated with each phase of the cell cycle. Although the broad outlines of these gene clusters were described nearly 20 years ago, new technologies have enabled major advances in our understanding of the genes comprising those clusters, their regulation, and the complex regulatory interplay between clusters. More recently, advances are being made in understanding the roles of chromatin in the control of the transcriptional program. We are also beginning to discover important regulatory interactions between the cell-cycle transcriptional program and other cell-cycle regulatory mechanisms such as checkpoints and metabolic networks. Here we review recent advances and contemporary models of the transcriptional network and consider these models in the context of eukaryotic cell-cycle controls. PMID:24395825

  10. DNA replication and damage checkpoints and meiotic cell cycle controls in the fission and budding yeasts.

    PubMed Central

    Murakami, H; Nurse, P

    2000-01-01

    The cell cycle checkpoint mechanisms ensure the order of cell cycle events to preserve genomic integrity. Among these, the DNA-replication and DNA-damage checkpoints prevent chromosome segregation when DNA replication is inhibited or DNA is damaged. Recent studies have identified an outline of the regulatory networks for both of these controls, which apparently operate in all eukaryotes. In addition, it appears that these checkpoints have two arrest points, one is just before entry into mitosis and the other is prior to chromosome separation. The former point requires the central cell-cycle regulator Cdc2 kinase, whereas the latter involves several key regulators and substrates of the ubiquitin ligase called the anaphase promoting complex. Linkages between these cell-cycle regulators and several key checkpoint proteins are beginning to emerge. Recent findings on post-translational modifications and protein-protein interactions of the checkpoint proteins provide new insights into the checkpoint responses, although the functional significance of these biochemical properties often remains unclear. We have reviewed the molecular mechanisms acting at the DNA-replication and DNA-damage checkpoints in the fission yeast Schizosaccharomyces pombe, and the modifications of these controls during the meiotic cell cycle. We have made comparisons with the controls in fission yeast and other organisms, mainly the distantly related budding yeast. PMID:10861204

  11. A limit-cycle self-organizing map architecture for stable arm control.

    PubMed

    Huang, Di-Wei; Gentili, Rodolphe J; Katz, Garrett E; Reggia, James A

    2017-01-01

    Inspired by the oscillatory nature of cerebral cortex activity, we recently proposed and studied self-organizing maps (SOMs) based on limit cycle neural activity in an attempt to improve the information efficiency and robustness of conventional single-node, single-pattern representations. Here we explore for the first time the use of limit cycle SOMs to build a neural architecture that controls a robotic arm by solving inverse kinematics in reach-and-hold tasks. This multi-map architecture integrates open-loop and closed-loop controls that learn to self-organize oscillatory neural representations and to harness non-fixed-point neural activity even for fixed-point arm reaching tasks. We show through computer simulations that our architecture generalizes well, achieves accurate, fast, and smooth arm movements, and is robust in the face of arm perturbations, map damage, and variations of internal timing parameters controlling the flow of activity. A robotic implementation is evaluated successfully without further training, demonstrating for the first time that limit cycle maps can control a physical robot arm. We conclude that architectures based on limit cycle maps can be organized to function effectively as neural controllers. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Resistance Torque Based Variable Duty-Cycle Control Method for a Stage II Compressor

    NASA Astrophysics Data System (ADS)

    Zhong, Meipeng; Zheng, Shuiying

    2017-07-01

    The resistance torque of a piston stage II compressor generates strenuous fluctuations in a rotational period, and this can lead to negative influences on the working performance of the compressor. To restrain the strenuous fluctuations in the piston stage II compressor, a variable duty-cycle control method based on the resistance torque is proposed. A dynamic model of a stage II compressor is set up, and the resistance torque and other characteristic parameters are acquired as the control targets. Then, a variable duty-cycle control method is applied to track the resistance torque, thereby improving the working performance of the compressor. Simulated results show that the compressor, driven by the proposed method, requires lower current, while the rotating speed and the output torque remain comparable to the traditional variable-frequency control methods. A variable duty-cycle control system is developed, and the experimental results prove that the proposed method can help reduce the specific power, input power, and working noise of the compressor to 0.97 kW·m-3·min-1, 0.09 kW and 3.10 dB, respectively, under the same conditions of discharge pressure of 2.00 MPa and a discharge volume of 0.095 m3/min. The proposed variable duty-cycle control method tracks the resistance torque dynamically, and improves the working performance of a Stage II Compressor. The proposed variable duty-cycle control method can be applied to other compressors, and can provide theoretical guidance for the compressor.

  13. p53 as Batman: using a movie plot to understand control of the cell cycle.

    PubMed

    Gadi, Nikhita; Foley, Sage E; Nowey, Mark; Plopper, George E

    2013-04-16

    This Teaching Resource provides and describes a two-part classroom exercise to help students understand control of the cell cycle, with a focus on the transcription factor p53, the E3 ubiquitin ligase Mdm2, the Mdm2 inhibitor ARF, the kinases ATM and ATR, the kinase Chk2, and the cell cycle inhibitor p21(Cip1). Students use characters and scenes from the movie The Dark Knight to represent elements of the cell cycle control machinery, then they apply these characters and scenes to translate a primary research article on p53 function into a new movie scene in the "Batman universe." This exercise is appropriate for college-level courses in cell biology and cancer biology and requires students to have a background in introductory cell biology. Explicit learning outcomes and associated assessment methods are provided, as well as slides, student assignments, the primary research article, and an instructor's guide for the exercise.

  14. AS160 controls eukaryotic cell cycle and proliferation by regulating the CDK inhibitor p21.

    PubMed

    Gongpan, Pianchou; Lu, Yanting; Wang, Fang; Xu, Yuhui; Xiong, Wenyong

    2016-07-02

    AS160 (TBC1D4) has been implicated in multiple biological processes. However, the role and the mechanism of action of AS160 in the regulation of cell proliferation remain unclear. In this study, we demonstrated that AS160 knockdown led to blunted cell proliferation in multiple cell types, including fibroblasts and cancer cells. The results of cell cycle analysis showed that these cells were arrested in the G1 phase. Intriguingly, this inhibition of cell proliferation and the cell cycle arrest caused by AS160 depletion were glucose independent. Moreover, AS160 silencing led to a marked upregulation of the expression of the cyclin-dependent kinase inhibitor p21. Furthermore, whereas AS160 overexpression resulted in p21 downregulation and rescued the arrested cell cycle in AS160-depeleted cells, p21 silencing rescued the inhibited cell cycle and proliferation in the cells. Thus, our results demonstrated that AS160 regulates glucose-independent eukaryotic cell proliferation through p21-dependent control of the cell cycle, and thereby revealed a molecular mechanism of AS160 modulation of cell cycle and proliferation that is of general physiological significance.

  15. Optimum Duty Cycle of Unsteady Plasma Aerodynamic Actuation for NACA0015 Airfoil Stall Separation Control

    NASA Astrophysics Data System (ADS)

    Sun, Min; Yang, Bo; Peng, Tianxiang; Lei, Mingkai

    2016-06-01

    Unsteady dielectric barrier discharge (DBD) plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA0015 airfoil by measuring the surface pressure distribution of the airfoil. The performance of the DBD aerodynamic actuation for airfoil stall separation suppression is evaluated under DBD voltages from 2000 V to 4000 V and the duty cycles varied in the range of 0.1 to 1.0. It is found that higher lift coefficients and lower threshold voltages are achieved under the unsteady DBD aerodynamic actuation with the duty cycles less than 0.5 as compared to that of the steady plasma actuation at the same free-stream speeds and attack angles, indicating a better flow control performance. By comparing the lift coefficients and the threshold voltages, an optimum duty cycle is determined as 0.25 by which the maximum lift coefficient and the minimum threshold voltage are obtained at the same free-stream speed and attack angle. The non-uniform DBD discharge with stronger discharge in the positive half cycle due to electrons deposition on the dielectric slabs and the suppression of opposite momentum transfer due to the intermittent discharge with cutoff of the negative half cycle are responsible for the observed optimum duty cycle. supported by National Natural Science Foundation of China (No. 21276036), Liaoning Provincial Natural Science Foundation of China (No. 2015020123) and the Fundamental Research Funds for the Central Universities of China (No. 3132015154)

  16. DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A NATURAL BIO-DEFENSE MECHANISM

    EPA Science Inventory

    DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A natural bio-defense mechanism
    Anuradha Mudipalli.

    Maintenance of genetic information, including the correct sequence of nucleotides in DNA, is essential for replication, gene expression, and protein synthesis. DNA lesions onto...

  17. STUDIES ON THE LIFE-CYCLE OF PARAGONIMUS AND THE CONTROL OF PARAGONIMIASIS IN SHIKOKU AREA.

    DTIC Science & Technology

    The life cycle, classification, pathology and control of the lung fluke, Paragonimus westermani, has been studied. Research is presented on the...paragonimiasis by partial research in the study area. It was clarified that this area is one of the highest infected areas with Paragonimus westermani in Japan.

  18. Life cycle and control of the cyst nematode Heterodera goldeni on rice in Egypt

    USDA-ARS?s Scientific Manuscript database

    The life cycle and methods for control of the cyst nematode Heterodera goldeni on rice (Oryza sativa) were examined in the greenhouse. Three tests were conducted to study the effects of soil treatments with some plant materials, stems of oyster mushroom (Pleurotus ostreatus), the biocontrol agent Ba...

  19. DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A NATURAL BIO-DEFENSE MECHANISM

    EPA Science Inventory

    DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A natural bio-defense mechanism
    Anuradha Mudipalli.

    Maintenance of genetic information, including the correct sequence of nucleotides in DNA, is essential for replication, gene expression, and protein synthesis. DNA lesions onto...

  20. Acute effect of cycling intervention on carotid arterial hemodynamics: basketball athletes versus sedentary controls

    PubMed Central

    2015-01-01

    Objective To compare the acute effects of a cycling intervention on carotid arterial hemodynamics between basketball athletes and sedentary controls. Methods Ten young long-term trained male basketball athletes (BA) and nine age-matched male sedentary controls (SC) successively underwent four bouts of exercise on a bicycle ergometer at the same workload. Hemodynamic variables at right common carotid artery were determined at rest and immediately following each bout of exercise. An ANCOVA was used to compare differences between the BA and SC groups at rest and immediately following the cycling intervention. The repeated ANOVA was used to assess differences between baseline and each bout of exercise within the BA or SC group. Results In both groups, carotid hemodynamic variables showed significant differences at rest and immediately after the cycling intervention. At rest, carotid arterial stiffness was significantly decreased and carotid arterial diameter was significantly increased in the BA group as compared to the SC group. Immediately following the cycling intervention, carotid arterial stiffness showed no obvious changes in the BA group but significantly increased in the SC group. It is worth noting that while arterial stiffness was lower in the BA group than in the SC group, the oscillatory shear index (OSI) was significantly higher in the BA group than in the SC group both at rest and immediately following the cycling intervention. Conclusion Long-term basketball exercise had a significant impact on common carotid arterial hemodynamic variables not only at rest but also after a cycling intervention. The role of OSI in the remodeling of arterial structure and function in the BA group at rest and after cycling requires clarification. PMID:25602805

  1. Acute effect of cycling intervention on carotid arterial hemodynamics: basketball athletes versus sedentary controls.

    PubMed

    Liu, Hai-Bin; Yuan, Wen-Xue; Qin, Kai-Rong; Hou, Jie

    2015-01-01

    To compare the acute effects of a cycling intervention on carotid arterial hemodynamics between basketball athletes and sedentary controls. Ten young long-term trained male basketball athletes (BA) and nine age-matched male sedentary controls (SC) successively underwent four bouts of exercise on a bicycle ergometer at the same workload. Hemodynamic variables at right common carotid artery were determined at rest and immediately following each bout of exercise. An ANCOVA was used to compare differences between the BA and SC groups at rest and immediately following the cycling intervention. The repeated ANOVA was used to assess differences between baseline and each bout of exercise within the BA or SC group. In both groups, carotid hemodynamic variables showed significant differences at rest and immediately after the cycling intervention. At rest, carotid arterial stiffness was significantly decreased and carotid arterial diameter was significantly increased in the BA group as compared to the SC group. Immediately following the cycling intervention, carotid arterial stiffness showed no obvious changes in the BA group but significantly increased in the SC group. It is worth noting that while arterial stiffness was lower in the BA group than in the SC group, the oscillatory shear index (OSI) was significantly higher in the BA group than in the SC group both at rest and immediately following the cycling intervention. Long-term basketball exercise had a significant impact on common carotid arterial hemodynamic variables not only at rest but also after a cycling intervention. The role of OSI in the remodeling of arterial structure and function in the BA group at rest and after cycling requires clarification.

  2. Redundancy or specificity? The role of the CDK Pho85 in cell cycle control

    PubMed Central

    Jiménez, Javier; Ricco, Natalia; Grijota-Martínez, Carmen; Fadó, Rut; Clotet, Josep

    2013-01-01

    It is generally accepted that progression through the eukaryotic cell cycle is driven by cyclin-dependent kinases (CDKs), which are regulated by interaction with oscillatory expressed proteins called cyclins. CDKs may be separated into 2 categories: essential and non-essential. Understandably, more attention has been focused on essential CDKs because they are shown to control cell cycle progression to a greater degree. After clearly determining the basic and “core” mechanisms of essential CDKs, several questions arise. What role do non-essential CDKs play? Are these CDKs functionally redundant and do they serve as a mere backup? Or might they be responsible for some accessory tasks in cell cycle progression or control? In the present review we will try to answer these questions based on recent findings on the involvement of non-essential CDKs in cell cycle progression. We will analyse the most recent information with regard to these questions in the yeast Saccharomyces cerevisiae, a well-established eukaryotic model, and in its unique non-essential CDK involved in the cell cycle, Pho85. We will also briefly extend our discussion to higher eukaryotic systems. PMID:24049669

  3. Coordinate developmental control of the meiotic cell cycle and spermatid differentiation in Drosophila males.

    PubMed

    Lin, T Y; Viswanathan, S; Wood, C; Wilson, P G; Wolf, N; Fuller, M T

    1996-04-01

    Wild-type function of four Drosophila genes, spermatocyte arrest, cannonball, always early and meiosis I arrest, is required both for cell-cycle progression through the G2/M transition of meiosis I in males and for onset of spermatid differentiation. In males mutant for any one of these meiotic arrest genes, mature primary spermatocytes with partially condensed chromosomes accumulate and postmeiotic cells are lacking. The arrest in cell-cycle progression occurs prior to degradation of cyclin A protein. The block in spermatogenesis in these mutants is not simply a secondary consequence of meiotic cell-cycle arrest, as spermatid differentiation proceeds in males mutant for the cell cycle activating phosphatase twine. Instead, the arrest of both meiosis and spermiogenesis suggests a control point that may serve to coordinate the male meiotic cell cycle with the spermatid differentiation program. The phenotype of the Drosophila meiotic arrest mutants is strikingly similar to the histopathological features of meiosis I maturation arrest infertility in human males, suggesting that the control point may be conserved from flies to man.

  4. E2F Transcription Factors Control the Roller Coaster Ride of Cell Cycle Gene Expression.

    PubMed

    Thurlings, Ingrid; de Bruin, Alain

    2016-01-01

    Initially, the E2F transcription factor was discovered as a factor able to bind the adenovirus E2 promoter and activate viral genes. Afterwards it was shown that E2F also binds to promoters of nonviral genes such as C-MYC and DHFR, which were already known at that time to be important for cell growth and DNA metabolism, respectively. These findings provided the first clues that the E2F transcription factor might be an important regulator of the cell cycle. Since this initial discovery in 1987, several additional E2F family members have been identified, and more than 100 targets genes have been shown to be directly regulated by E2Fs, the majority of these are important for controlling the cell cycle. The progression of a cell through the cell cycle is accompanied with the increased expression of a specific set of genes during one phase of the cell cycle and the decrease of the same set of genes during a later phase of the cell cycle. This roller coaster ride, or oscillation, of gene expression is essential for the proper progression through the cell cycle to allow accurate DNA replication and cell division. The E2F transcription factors have been shown to be critical for the temporal expression of the oscillating cell cycle genes. This review will focus on how the oscillation of E2Fs and their targets is regulated by transcriptional, post-transcriptional and post-translational mechanism in mammals, yeast, flies, and worms. Furthermore, we will discuss the functional impact of E2Fs on the cell cycle progression and outline the consequences when E2F expression is disturbed.

  5. Temperature and the sulfur cycle control monomethylmercury cycling in high Arctic coastal marine sediments from Allen Bay, Nunavut, Canada.

    PubMed

    St Pierre, K A; Chétélat, J; Yumvihoze, E; Poulain, A J

    2014-01-01

    Monomethylmercury (MMHg) is a neurotoxin of concern in the Canadian Arctic due to its tendency to bioaccumulate and the importance of fish and wildlife in the Inuit diet. In lakes and wetlands, microbial sediment communities are integral to the cycling of MMHg; however, the role of Arctic marine sediments is poorly understood. With projected warming, the effect of temperature on the production and degradation of MMHg in Arctic environments also remains unclear. We examined MMHg dynamics across a temperature gradient (4, 12, 24 °C) in marine sediments collected in Allen Bay, Nunavut. Slurries were spiked with stable mercury isotopes and amended with specific microbial stimulants and inhibitors, and subsampled over 12 days. Maximal methylation and demethylation potentials were low, ranging from below detection to 1.13 pmol g(-1) h(-1) and 0.02 pmol g(-1) h(-1), respectively, suggesting that sediments are likely not an important source of MMHg to overlying water. Our results suggest that warming may result in an increase in Hg methylation - controlled by temperature-dependent sulfate reduction, without a compensatory increase in demethylation. This study highlights the need for further research into the role of high Arctic marine sediments and climate on the Arctic marine MMHg budget.

  6. G1/S control of anchorage-independent growth in the fibroblast cell cycle

    PubMed Central

    1991-01-01

    We have developed methodology to identify the block to anchorage- independent growth and position it within the fibroblast cell cycle. Results with NRK fibroblasts show that mitogen stimulation of the G0/G1 transition and G1-associated increases in cell size are minimally affected by loss of cell anchorage. In contrast, the induction of G1/S cell cycle genes and DNA synthesis is markedly inhibited when anchorage is blocked. Moreover, we demonstrate that the anchorage-dependent transition maps to late G1 and shortly before activation of the G1/S p34cdc2-like kinase. The G1/S block was also detectable in NIH-3T3 cells. Our results: (a) distinguish control of cell cycle progression by growth factors and anchorage; (b) indicate that anchorage mediates G1/S control in fibroblasts; and (c) identify a physiologic circumstance in which the phenotype of mammalian cell cycle arrest would closely resemble Saccharomyces cerevisiae START. The close correlation between anchorage independence in vitro and tumorigenicity in vivo emphasizes the key regulatory role for G1/S control in mammalian cells. PMID:1955482

  7. Ecological controls on water-cycle response to climate variability in deserts.

    PubMed

    Scanlon, B R; Levitt, D G; Reedy, R C; Keese, K E; Sully, M J

    2005-04-26

    The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Nino southern oscillation in the Mojave Desert. Extreme El Nino winter precipitation (2.3-2.5 times normal) typical of the U.S. Southwest would be expected to increase groundwater recharge, which is critical for water resources in semiarid and arid regions. However, lysimeter data indicate that rapid increases in vegetation productivity in response to elevated winter precipitation reduced soil water storage to half of that in a nonvegetated lysimeter, thereby precluding deep drainage below the root zone that would otherwise result in groundwater recharge. Vegetation dynamics have been controlling the water cycle in interdrainage desert areas throughout the U.S. Southwest, maintaining dry soil conditions and upward soil water flow since the last glacial period (10,000-15,000 yr ago), as shown by soil water chloride accumulations. Although measurements are specific to the U.S. Southwest, correlations between satellite-based vegetation productivity and elevated precipitation related to El Nino southern oscillation indicate this model may be applicable to desert basins globally. Understanding the two-way coupling between vegetation dynamics and the water cycle is critical for predicting how climate variability influences hydrology and water resources in water-limited landscapes.

  8. Environmental control interventions for frontotemporal dementia with reversed sleep-wake cycles.

    PubMed

    Yamakawa, Miyae; Shigenobu, Kazue; Makimoto, Kiyoko; Zhu, Canqun; Ashida, Nobuyuki; Tabushi, Kaoru

    2008-01-01

    This study aimed to evaluate the effectiveness of environmental control interventions using an integrated chip tag monitoring system for a frontotemporal dementia (FTD) patient. The subject was a male FTD patient (Pick type) with reversed sleep-wake cycles. For a 2-week period, the doors to all patients' rooms in the unit were kept open as a form of environmental control, and in the following 2 weeks, all doors were kept closed (intervention A). To increase his activity levels, a staff walked with him for 2 weeks (intervention B), while all the doors to patients' rooms in the unit were kept closed. In intervention A, daytime ambulation increased, whereas nighttime ambulation decreased significantly. During intervention B, nighttime ambulation increased significantly. Environmental controls seem to be effective for restoring sleep-wake cycles in even an advanced-stage FTD patient, whereas exercise program by the staff aggravated the problem.

  9. A quantitative model of the switch cycle of an archaeal flagellar motor and its sensory control.

    PubMed

    Nutsch, Torsten; Oesterhelt, Dieter; Gilles, Ernst Dieter; Marwan, Wolfgang

    2005-10-01

    By reverse-engineering we have detected eight kinetic phases of the symmetric switch cycle of the Halobacterium salinarum flagellar motor assembly and identified those steps in the switch cycle that are controlled by sensory rhodopsins during phototaxis. Upon switching the rotational sense, the flagellar motor assembly passes through a stop state from which all subunits synchronously resume rotation in the reverse direction. The assembly then synchronously proceeds through three subsequent functional states of the switch: Refractory, Competent, and Active, from which the rotational sense is switched again. Sensory control of the symmetric switch cycle occurs at two steps in each rotational sense by inversely regulating the probabilities for a change from the Refractory to the Competent and from Competent to the Active rotational mode. We provide a mathematical model for flagellar motor switching and its sensory control, which is able to explain all tested experimental results on spontaneous and light-controlled motor switching, and give a mechanistic explanation based on synchronous conformational transitions of the subunits of the switch complex after reversible dissociation and binding of a response regulator (CheYP). We conclude that the kinetic mechanism of flagellar motor switching and its sensory control is fundamentally different in the archaeon H. salinarum and the bacterium Escherichia coli.

  10. SAMHD1 controls cell cycle status, apoptosis and HIV-1 infection in monocytic THP-1 cells.

    PubMed

    Bonifati, Serena; Daly, Michele B; St Gelais, Corine; Kim, Sun Hee; Hollenbaugh, Joseph A; Shepard, Caitlin; Kennedy, Edward M; Kim, Dong-Hyun; Schinazi, Raymond F; Kim, Baek; Wu, Li

    2016-08-01

    SAMHD1 limits HIV-1 infection in non-dividing myeloid cells by decreasing intracellular dNTP pools. HIV-1 restriction by SAMHD1 in these cells likely prevents activation of antiviral immune responses and modulates viral pathogenesis, thus highlighting a critical role of SAMHD1 in HIV-1 physiopathology. Here, we explored the function of SAMHD1 in regulating cell proliferation, cell cycle progression and apoptosis in monocytic THP-1 cells. Using the CRISPR/Cas9 technology, we generated THP-1 cells with stable SAMHD1 knockout. We found that silencing of SAMHD1 in cycling cells stimulates cell proliferation, redistributes cell cycle population in the G1/G0 phase and reduces apoptosis. These alterations correlated with increased dNTP levels and more efficient HIV-1 infection in dividing SAMHD1 knockout cells relative to control. Our results suggest that SAMHD1, through its dNTPase activity, affects cell proliferation, cell cycle distribution and apoptosis, and emphasize a key role of SAMHD1 in the interplay between cell cycle regulation and HIV-1 infection. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. SAMHD1 controls cell cycle status, apoptosis and HIV-1 infection in monocytic THP-1 cells

    SciTech Connect

    Bonifati, Serena; Daly, Michele B.; St Gelais, Corine; Kim, Sun Hee; Hollenbaugh, Joseph A.; Shepard, Caitlin; Kennedy, Edward M.; Kim, Dong-Hyun; Schinazi, Raymond F.; Kim, Baek; Wu, Li

    2016-08-15

    SAMHD1 limits HIV-1 infection in non-dividing myeloid cells by decreasing intracellular dNTP pools. HIV-1 restriction by SAMHD1 in these cells likely prevents activation of antiviral immune responses and modulates viral pathogenesis, thus highlighting a critical role of SAMHD1 in HIV-1 physiopathology. Here, we explored the function of SAMHD1 in regulating cell proliferation, cell cycle progression and apoptosis in monocytic THP-1 cells. Using the CRISPR/Cas9 technology, we generated THP-1 cells with stable SAMHD1 knockout. We found that silencing of SAMHD1 in cycling cells stimulates cell proliferation, redistributes cell cycle population in the G{sub 1}/G{sub 0} phase and reduces apoptosis. These alterations correlated with increased dNTP levels and more efficient HIV-1 infection in dividing SAMHD1 knockout cells relative to control. Our results suggest that SAMHD1, through its dNTPase activity, affects cell proliferation, cell cycle distribution and apoptosis, and emphasize a key role of SAMHD1 in the interplay between cell cycle regulation and HIV-1 infection.

  12. Cyclin A expression is under negative transcriptional control during the cell cycle.

    PubMed Central

    Huet, X; Rech, J; Plet, A; Vié, A; Blanchard, J M

    1996-01-01

    Transcription of the gene coding for cyclin A, a protein required for S-phase transit, is cell cycle regulated and is restricted to proliferating cells. To further explore transcriptional regulation linked to cell division cycle control, a genomic clone containing 5' flanking sequences of the murine cyclin A gene was isolated. When it was fused to a luciferase reporter gene, it was shown to function as a proliferation-regulated promoter in NIH 3T3 cells. Transcription of the mouse cyclin A gene is negatively regulated by arrest of cell proliferation. A mutation of a GC-rich sequence conserved between mice and humans is sufficient to relieve transcriptional repression, resulting in a promoter with constitutively high activity. In agreement with this result, in vivo footprinting reveals a protection of the cell cycle-responsive element in G0/early G1 cells which is not observed at later stages of the cell cycle. Moreover, the footprint is present in dimethyl sulfoxide-induced differentiating and not in proliferating Friend erythroleukemia cells. Conversely, two other sites, which in vitro bind ATF-1 and NF-Y, respectively, are constitutively occupied throughout cell cycle progression. PMID:8668196

  13. Exfoliation Propensity of Oxide Scale in Heat Exchangers Used for Supercritical CO2 Power Cycles

    SciTech Connect

    Sabau, Adrian S; Shingledecker, John P.; Kung, Steve; Wright, Ian G.; Nash, Jim

    2016-01-01

    Supercritical CO2 (sCO2) Brayton cycle systems offer the possibility of improved efficiency in future fossil energy power generation plants operating at temperatures of 650 C and above. As there are few data on the oxidation/corrosion behavior of structural alloys in sCO2 at these temperatures, modeling to predict the propensity for oxide exfoliation is not well developed, thus hindering materials selection for these novel cycles. The ultimate goal of this effort is to provide needed data on scale exfoliation behavior in sCO2 for confident alloy selection. To date, a model developed by ORNL and EPRI for the exfoliation of oxide scales formed on boiler tubes in high-temperature, high-pressure steam has proven useful for managing exfoliation in conventional steam plants. A major input provided by the model is the ability to predict the likelihood of scale failure and loss based on understanding of the evolution of the oxide morphologies and the conditions that result in susceptibility to exfoliation. This paper describes initial steps taken to extend the existing model for exfoliation of steam-side oxide scales to sCO2 conditions. The main differences between high-temperature, high-pressure steam and sCO2 that impact the model involve (i) significant geometrical differences in the heat exchangers, ranging from standard pressurized tubes seen typically in steam-producing boilers to designs for sCO2 that employ variously-curved thin walls to create shaped flow paths for extended heat transfer area and small channel cross-sections to promote thermal convection and support pressure loads; (ii) changed operating characteristics with sCO2 due to the differences in physical and thermal properties compared to steam; and (iii) possible modification of the scale morphologies, hence properties that influence exfoliation behavior, due to reaction with carbon species from sCO2. The numerical simulations conducted were based on an assumed sCO2 operating schedule and several

  14. Polo kinase links the stress pathway to cell cycle control and tip growth in fission yeast.

    PubMed

    Petersen, Janni; Hagan, Iain M

    2005-05-26

    Stress-activated mitogen-activated protein kinase cascades instigate a range of changes to enable eukaryotic cells to cope with particular insults. In Schizosaccharomyces pombe these responses include the transcription of specific gene sets and inhibition of entry into mitosis. The S. pombe stress response pathway (SRP) also promotes commitment to mitosis in unperturbed cell cycles to allow cells to match their rate of division with nutrient availability. The nature of this SRP function in cell cycle control is unknown. Entry into mitosis is controlled by mitosis-promoting factor (MPF; Cdc2/cyclin B) activity. Inhibitory phosphorylation of Cdc2 by Wee1 kinase inactivates MPF until Cdc25 removes this phosphate to promote mitosis. The balance between Wee1 and Cdc25 activities is influenced by the recruitment of polo kinase (Plo1) to the spindle pole body (SPB). The SPB component Cut12 mediates this recruitment. Hyper-activating mutations in either cut12 or plo1 enable Cdc25-defective cells to enter mitosis. The hyperactive cut12.s11 mutation suppresses cdc25.22, as it promotes recruitment of active Plo1 to interphase SPBs. Here we show that the SRP promotes phosphorylation of Plo1 on Ser 402. In unperturbed cell cycles, SRP-mediated phosphorylation of Ser 402 promotes Plo1 recruitment to SPBs and thus commitment to mitosis. Ser 402 phosphorylation also ensures efficient reinitiation of cell tip growth and cell division during recovery from particular stresses. Thus, phosphorylation of Plo1 Ser 402 not only enables SRP signalling to modulate the timing of mitotic commitment in response to nutrient status in unperturbed cycles, but also promotes the return to normal cell cycle control after stress.

  15. Intelligent approach for parallel HEV control strategy based on driving cycles

    NASA Astrophysics Data System (ADS)

    Montazeri-Gh, M.; Asadi, M.

    2011-02-01

    This article describes a methodological approach for the intelligent control of parallel hybrid electric vehicle (HEV) by the inclusion of the concept of driving cycles. In this approach, a fuzzy logic controller is designed to manage the internal combustion engine to work in the vicinity of its optimal condition instantaneously. In addition, based on the definition of microtrip, several driving patterns are classified that represent the congested to highway traffic conditions. The driving cycle and traffic conditions are then incorporated in an optimisation process to tune the fuzzy membership function parameters. In this study, the optimisation process is formulated to minimise the HEV fuel consumption (FC) and emissions as well as the satisfaction of the driving performance constraints. Finally, optimisation results are provided for three different driving cycles including ECE-EUDC, FTP and TEH-CAR. TEH-CAR is a driving cycle that is developed based on the experimental data collected from the real traffic condition in the city of Tehran. The results from the computer simulation show the effectiveness of the approach and reduction in FC and emissions while ensuring that the vehicle performance is not sacrificed.

  16. Avulsion cycles and their stratigraphic signature on an experimental backwater-controlled delta

    NASA Astrophysics Data System (ADS)

    Ganti, Vamsi; Chadwick, Austin J.; Hassenruck-Gudipati, Hima J.; Lamb, Michael P.

    2016-09-01

    River deltas grow in large part through repeated cycles of lobe construction and channel avulsion. Understanding avulsion cycles is important for coastal restoration and ecology, land management, and flood hazard mitigation. Emerging theories suggest that river avulsions on lowland deltas are controlled by backwater hydrodynamics; however, our knowledge of backwater-controlled avulsion cycles is limited. Here we present results from an experimental delta that evolved under persistent backwater hydrodynamics achieved through variable flood discharges, shallow bed slopes, and subcritical flows. The experimental avulsion cycles consisted of an initial phase of avulsion setup, an avulsion trigger, selection of a new flow path, and abandonment of the parent channel. Avulsions were triggered during the largest floods (78% of avulsions) after the channel was filled by a fraction (0.3 ± 0.13) of its characteristic flow depth at the avulsion site, which occurred in the upstream part of the backwater zone. The new flow path following avulsion was consistently one of the shortest paths to the shoreline, and channel abandonment occurred through temporal decline in water flow and sediment delivery to the parent channel. Experimental synthetic stratigraphy indicates that bed thicknesses were maximum at the avulsion sites, consistent with our morphologic measurements of avulsion setup and the idea that there is a record of avulsion locations and thresholds in sedimentary rocks. Finally, we discuss the implications of our findings within the context of sustainable management of deltas, their stratigraphic record, and predicting avulsions on deltas.

  17. Mycorrhizal Controls on Nitrogen Uptake Drive Carbon Cycling at the Global Scale

    NASA Astrophysics Data System (ADS)

    Shi, M.; Fisher, J. B.; Brzostek, E. R.; Phillips, R.

    2015-12-01

    Nearly all plants form symbiotic relationships with one of two types of mycorrhizal fungi—arbuscular mycorrhizae (AM) and ectomycorrhizal (ECM) fungi, which are essential to global biogeochemical cycling of nutrient elements. In soils with higher rates of nitrogen and phosphorus mineralization from organic matter, AM-associated plants can be better adapted than ECM-associated plants. Importantly, the photosynthate costs of nutrient uptake for AM-associated plants are usually lower than that for ECM-associated plants. Thus, the global carbon cycle is closely coupled with mycorrhizal controls on N uptake. To investigate the potential climate dependence of terrestrial environments from AM- and ECM-associated plants, this study uses the Community Atmosphere Model (CAM) with a plant productivity-optimized N acquisition model—the Fixation and Uptake of Nitrogen (FUN) model—integrated into its land model—the Community Land Model (CLM). This latest version of CLM coupled with FUN allows for the assessment of mycorrhizal controls on global biogeochemical cycling. Here, we show how the historical evolution of AM- and ECM-associations altered regional and global biogeochemical cycling and climate, and future projections over the next century.

  18. Hit the right spots: cell cycle control by phosphorylated guanosines in alphaproteobacteria.

    PubMed

    Hallez, Régis; Delaby, Marie; Sanselicio, Stefano; Viollier, Patrick H

    2017-03-01

    The class Alphaproteobacteria includes Gram-negative free-living, symbiotic and obligate intracellular bacteria, as well as important plant, animal and human pathogens. Recent work has established the key antagonistic roles that phosphorylated guanosines, cyclic-di-GMP (c-di-GMP) and the alarmones guanosine tetraphosphate and guanosine pentaphosphate (collectively referred to as (p)ppGpp), have in the regulation of the cell cycle in these bacteria. In this Review, we discuss the insights that have been gained into the regulation of the initiation of DNA replication and cytokinesis by these second messengers, with a particular focus on the cell cycle of Caulobacter crescentus. We explore how the fluctuating levels of c-di-GMP and (p)ppGpp during the progression of the cell cycle and under conditions of stress control the synthesis and proteolysis of key regulators of the cell cycle. As these signals also promote bacterial interactions with host cells, the enzymes that control (p)ppGpp and c-di-GMP are attractive antibacterial targets.

  19. Genes involved in cell cycle G1 checkpoint control are frequently mutated in human melanoma metastases.

    PubMed Central

    Platz, A.; Sevigny, P.; Norberg, T.; Ring, P.; Lagerlöf, B.; Ringborg, U.

    1996-01-01

    A common characteristic of cancer cells is unrestrained cell division. This may be caused by mutational changes in genes coding for components of cell cycle-controlling networks. Alterations in genes involved in G1 checkpoint control have been registered in many human tumours, and investigations from several laboratories show that such alterations, taken together, are the most frequent changes detected in cancer cells. The present paper describes mutational analysis by polymerase chain reaction-single-strand conformation polymorphism (PCR/SSCP) and nucleotide sequence analysis of the genes coding for the p15, p53 and N-ras proteins in 26 metastases from 25 melanoma patients. The registered mutation frequencies add together with previously registered mutations in p16 in the same patient samples to a substantial total frequency of 44% of patients with mutation in at least one of the investigated genes. These results show the occurrence of heterogeneous defects among components of the cell cycle controlling machinery in a human melanoma tumour sample collection and demonstrate that the total frequency of detected alterations increases with the number of cell cycle controlling genes included in the screening panel. Images Figure 1 PMID:8826861

  20. Controls on aquatic carbon cycling in a carbonate dominated groundwater catchment using dissolved oxygen dynamics

    NASA Astrophysics Data System (ADS)

    Butler, A. P.; Parker, S. J.

    2015-12-01

    Carbon cycling in aquatic systems is increasingly seen as playing an important role in global carbon budgets and hence on potential impacts and controls on global warming. However, determining the partitioning within and transfer between different carbon stores is a major challenge, particularly where there are multiple sources and controls on carbon utilisation. Dissolved oxygen, DO, provides a proxy for investigating the dynamics of carbon utilisation in aquatic systems. High temporal resolution monitoring of DO at multiple site on the Hampshire Avon, a chalk dominated permeable catchment in southern England, UK, has been investigated using a dynamic DO model in order to investigate the biochemical cycling of carbon. Gross primary production, governed by photosynthetically active radiation, is determined through inverse modelling. Model simplification though parameter reduction is achieved through investigating controls on aeration (the transfer of oxygen across the atmosphere-river interface) and respiration. Seasonal changes in biomass affect long term oxygen dynamics, which are compounded by episodic hydrological events that control the partitioning of surface water and groundwater in the stream channel and consequently the sources of carbon and DO in the river channel. Using variations in surface geology across the catchment the impacts of varying baseflow characteristics on carbon cycling within the catchment is demonstrated.

  1. A pH-regulated quality control cycle for surveillance of secretory protein assembly.

    PubMed

    Vavassori, Stefano; Cortini, Margherita; Masui, Shoji; Sannino, Sara; Anelli, Tiziana; Caserta, Imma R; Fagioli, Claudio; Mossuto, Maria F; Fornili, Arianna; van Anken, Eelco; Degano, Massimo; Inaba, Kenji; Sitia, Roberto

    2013-06-27

    To warrant the quality of the secretory proteome, stringent control systems operate at the endoplasmic reticulum (ER)-Golgi interface, preventing the release of nonnative products. Incompletely assembled oligomeric proteins that are deemed correctly folded must rely on additional quality control mechanisms dedicated to proper assembly. Here we unveil how ERp44 cycles between cisGolgi and ER in a pH-regulated manner, patrolling assembly of disulfide-linked oligomers such as IgM and adiponectin. At neutral, ER-equivalent pH, the ERp44 carboxy-terminal tail occludes the substrate-binding site. At the lower pH of the cisGolgi, conformational rearrangements of this peptide, likely involving protonation of ERp44's active cysteine, simultaneously unmask the substrate binding site and -RDEL motif, allowing capture of orphan secretory protein subunits and ER retrieval via KDEL receptors. The ERp44 assembly control cycle couples secretion fidelity and efficiency downstream of the calnexin/calreticulin and BiP-dependent quality control cycles.

  2. A pH-Regulated Quality Control Cycle for Surveillance of Secretory Protein Assembly

    PubMed Central

    Vavassori, Stefano; Cortini, Margherita; Masui, Shoji; Sannino, Sara; Anelli, Tiziana; Caserta, Imma R.; Fagioli, Claudio; Mossuto, Maria F.; Fornili, Arianna; van Anken, Eelco; Degano, Massimo; Inaba, Kenji; Sitia, Roberto

    2013-01-01

    Summary To warrant the quality of the secretory proteome, stringent control systems operate at the endoplasmic reticulum (ER)-Golgi interface, preventing the release of nonnative products. Incompletely assembled oligomeric proteins that are deemed correctly folded must rely on additional quality control mechanisms dedicated to proper assembly. Here we unveil how ERp44 cycles between cisGolgi and ER in a pH-regulated manner, patrolling assembly of disulfide-linked oligomers such as IgM and adiponectin. At neutral, ER-equivalent pH, the ERp44 carboxy-terminal tail occludes the substrate-binding site. At the lower pH of the cisGolgi, conformational rearrangements of this peptide, likely involving protonation of ERp44’s active cysteine, simultaneously unmask the substrate binding site and −RDEL motif, allowing capture of orphan secretory protein subunits and ER retrieval via KDEL receptors. The ERp44 assembly control cycle couples secretion fidelity and efficiency downstream of the calnexin/calreticulin and BiP-dependent quality control cycles. PMID:23685074

  3. Method for controlling start-up and steady state performance of a closed split flow recompression brayton cycle

    DOEpatents

    Pasch, James Jay

    2017-02-07

    A method of resolving a balanced condition that generates control parameters for start-up and steady state operating points and various component and cycle performances for a closed split flow recompression cycle system. The method provides for improved control of a Brayton cycle thermal to electrical power conversion system. The method may also be used for system design, operational simulation and/or parameter prediction.

  4. Reference H Cycle 3 Stability, Control, and Flying Qualities Batch Assessments

    NASA Technical Reports Server (NTRS)

    Henderson, Dennis K.

    1999-01-01

    This work is an update of the assessment completed in February of 1996, when a preliminary assessment report was issued for the Cycle 2B simulation model. The primary purpose of the final assessment was to re-evaluate each assessment against the flight control system (FCS) requirements document using the updated model. Only a limited number of final assessments were completed due to the close proximity of the release of the Langley model and the assessment deliverable date. The assessment used the nonlinear Cycle 3 simulation model because it combines nonlinear aeroelastic (quasi-static) aerodynamic with hinge moment and rate limited control surface deflections. Both Configuration Aerodynamics (Task 32) and Flight Controls (Task 36) were funded in 1996 to conduct the final stability and control assessments of the unaugmented Reference H configuration in FY96. Because the two tasks had similar output requirements, the work was divided such that Flight Controls would be responsible for the implementation and checkout of the simulation model and Configuration Aerodynamics for writing Madab "script' files, conducting the batch assessments and writing the assessment report. Additionally, Flight Controls was to investigate control surface allocations schemes different from the baseline Reference H in an effort to fulfill flying qualities criteria.

  5. Reference H Cycle 3 Stability, Control, and Flying Qualities Batch Assessments

    NASA Technical Reports Server (NTRS)

    Henderson, Dennis K.

    1999-01-01

    This work is an update of the assessment completed in February of 1996, when a preliminary assessment report was issued for the Cycle 2B simulation model. The primary purpose of the final assessment was to re-evaluate each assessment against the flight control system (FCS) requirements document using the updated model. Only a limited number of final assessments were completed due to the close proximity of the release of the Langley model and the assessment deliverable date. The assessment used the nonlinear Cycle 3 simulation model because it combines nonlinear aeroelastic (quasi-static) aerodynamic with hinge moment and rate limited control surface deflections. Both Configuration Aerodynamics (Task 32) and Flight Controls (Task 36) were funded in 1996 to conduct the final stability and control assessments of the unaugmented Reference H configuration in FY96. Because the two tasks had similar output requirements, the work was divided such that Flight Controls would be responsible for the implementation and checkout of the simulation model and Configuration Aerodynamics for writing Madab "script' files, conducting the batch assessments and writing the assessment report. Additionally, Flight Controls was to investigate control surface allocations schemes different from the baseline Reference H in an effort to fulfill flying qualities criteria.

  6. Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2013-01-01

    A dual flow-path inlet for a turbine based combined cycle (TBCC) propulsion system is to be tested in order to evaluate methodologies for performing a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms which are designed to maintain shock position during inlet disturbances. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the development of a mode transition schedule for the HiTECC simulation that is analogous to the development of inlet performance maps. Inlet performance maps, derived through experimental means, describe the performance and operability of the inlet as the splitter closes, switching power production from the turbine engine to the Dual Mode Scram Jet. With knowledge of the operability and performance tradeoffs, a closed loop system can be designed to optimize the performance of the inlet. This paper demonstrates the design of the closed loop control system and benefit with the implementation of a Proportional-Integral controller, an H-Infinity based controller, and a disturbance observer based controller; all of which avoid inlet unstart during a mode transition with a simulated disturbance that would lead to inlet unstart without closed loop control.

  7. Regulation of the Calvin cycle for CO2 fixation as an example for general control mechanisms in metabolic cycles.

    PubMed

    Fridlyand, L E; Scheibe, R

    1999-08-01

    The theory of a metabolic cycle with the main portion of its intermediates remaining inside the cycle during one turnover has been developed. On this basis, the regulation of the Calvin cycle is analyzed. It is demonstrated that not only the reactions of non-equilibrium enzymes, as the carboxylation of ribulose 1,5-bisphosphate, but reactions that operate close to a thermodynamic equilibrium, especially the reduction of 3-phosphoglycerate and the transketolase reaction can significantly influence the total turnover period in the Calvin cycle. The role of compensating mechanisms in the maintenance of the photosynthesis rate upon changes of environmental conditions and of enzyme contents is analyzed for the Calvin cycle. It is shown that the change of the total quantity of the metabolites is one of the main self-regulated mechanisms in the Calvin cycle. A change of the ATP/ADP ratio can be used by the cell to maintain the CO2 assimilation rate, when the total quantity of the metabolites is changed. The developed analysis permits to explain some experimental data obtained with transgenic plants with restricted efflux of carbon from the chloroplasts.

  8. Refrigerator with variable capacity compressor and cycle priming action through capacity control and associated methods

    DOEpatents

    Gomes, Alberto Regio; Litch, Andrew D.; Wu, Guolian

    2016-03-15

    A refrigerator appliance (and associated method) that includes a condenser, evaporator and a multi-capacity compressor. The appliance also includes a pressure reducing device arranged within an evaporator-condenser refrigerant circuit, and a valve system for directing or restricting refrigerant flow through the device. The appliance further includes a controller for operating the compressor upon the initiation of a compressor ON-cycle at a priming capacity above a nominal capacity for a predetermined or calculated duration.

  9. Passive Control of Limit Cycle Oscillations in a Thermoacoustic System using Asymmetry

    DTIC Science & Technology

    2006-09-05

    Passive Control of Limit Cycle Oscillations in a Thermoacoustic System using Asymmetry Bryan Eisenhower ∗ Gregory Hagen † Andrzej Banaszuk ‡ Igor...Mezić § September 5, 2006 Abstract In this paper we investigate oscillations of a dynamical system containing passive dynamics driven by a positive...motivation of this problem is thermoacoustic dynamics in a gas turbine combustor. The spatial domain is periodic (pas- sive annular acoustics) which are

  10. The use of prostaglandins in controlling estrous cycle of the ewe: a review.

    PubMed

    Fierro, Sergio; Gil, Jorge; Viñoles, Carolina; Olivera-Muzante, Julio

    2013-02-01

    This review considers the use of prostaglandin F(2α) and its synthetic analogues (PG) for controlling the estrous cycle of the ewe. Aspects such as phase of the estrus cycle, PG analogues, PG doses, ovarian follicle development pattern, CL formation, progesterone synthesis, ovulation rate, sperm transport, embryo quality, and fertility rates after PG administration are reviewed. Furthermore, protocols for estrus synchronization and their success in timed AI programs are discussed. Based on available information, the ovine CL is refractory to PG treatment for up to 2 days after ovulation. All PG analogues are effective when an appropriate dose is given; in that regard, there is a positive association between the dose administered and the proportion of ewes detected in estrus. Follicular response after PG is dependent on the phase of the estrous cycle at treatment. Altered sperm transport and low pregnancy rates are generally reported. However, reports on alteration of the steroidogenic capacity of preovulatory follicles, ovulation rate, embryo quality, recovery rates, and prolificacy, are controversial. Although various PG-based protocols can be used for estrus synchronization, a second PG injection improves estrus response when the stage of the estrous cycle at the first injection is unknown. The estrus cycle after PG administration has a normal length. Prostaglandin-based protocols for timed AI achieved poor reproductive outcomes, but increasing the interval between PG injections might increase pregnancy rates. Attempts to improve reproductive outcomes have been directed to provide a synchronized LH surge: use of different routes of AI (cervical or intrauterine), different PG doses, and increased intervals between PG injections. Finally we present our point of view regarding future perspectives on the use of PG in programs of controlled sheep reproduction. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Multi-scale controls on spatial variability in river biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jennifer; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

    2016-04-01

    Excessive nutrient concentrations are common in surface waters and groundwaters in agricultural catchments worldwide. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical cycling rates can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are largely unknown. Here, we aimed to assess: 1) how differences in river geomorphological heterogeneity control solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small scale targeted management interventions to alter geomorphic heterogeneity may be effective in creating hotspots of river biogeochemical cycling and nutrient load

  12. The role of perceived control over anxiety in prospective symptom reports across the menstrual cycle.

    PubMed

    Mahon, Jennifer N; Rohan, Kelly J; Nillni, Yael I; Zvolensky, Michael J

    2015-04-01

    The present investigation tested the role of psychological vulnerabilities to anxiety in reported menstrual symptom severity. Specifically, the current study tested the incremental validity of perceived control over anxiety-related events in predicting menstrual symptom severity, controlling for the effect of anxiety sensitivity, a documented contributor to menstrual distress. It was expected that women with lower perceived control over anxiety-related events would report greater menstrual symptom severity, particularly in the premenstrual phase. A sample of 49 normally menstruating women, aged 18-47 years, each prospectively tracked their menstrual symptoms for one cycle and completed the Anxiety Control Questionnaire (Rapee, Craske, Brown, & Barlow Behav Ther 27:279-293. doi: 10.1016/S0005-7894(96)80018-9 , 1996) in their follicular and premenstrual phases. A mixed model analysis revealed perceived control over anxiety-related events was a more prominent predictor of menstrual symptom severity than anxiety sensitivity, regardless of the current cycle phase. This finding provides preliminary evidence that perceived control over anxiety-related events is associated with the perceived intensity of menstrual symptoms. This finding highlights the role of psychological vulnerabilities in menstrual distress. Future research should examine whether psychological interventions that target cognitive vulnerabilities to anxiety may help reduce severe menstrual distress.

  13. Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle.

    PubMed

    Catta-Preta, Carolina M C; Brum, Felipe L; da Silva, Camila C; Zuma, Aline A; Elias, Maria C; de Souza, Wanderley; Schenkman, Sergio; Motta, Maria Cristina M

    2015-01-01

    Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number.

  14. A model for the central control of airflow patterns within the human nasal cycle.

    PubMed

    Williams, M; Eccles, R

    2016-01-01

    The nasal cycle exhibits mainly reciprocal changes in nasal airflow that may be controlled from centres in the hypothalamus and brainstem. This study aims to gather new knowledge about the nasal cycle to help develop a control model. Right and left nasal airflow was measured in healthy human subjects by rhinomanometry. This was performed over 7-hour periods on 2 study days separated by approximately 1 week. The correlation coefficient for nasal airflow was calculated for day 1 and day 2. Thirty subjects (mean age, 22.7 years) completed the study. The correlation coefficient for nasal airflow varied between r = 0.97 with in-phase changes in airflow and r = -0.89 with reciprocal changes in airflow. The majority of r values were negative, indicating reciprocal changes in airflow (50 out of 60). There was a tendency for r values to become more negative between day 1 and day 2 (p < 0.001). A control model involving a hypothalamic centre and two brainstem half centres is proposed to explain both the in-phase and reciprocal changes in airflow associated with the nasal cycle.

  15. Variations upon a theme: Australian lizards provide insights into the endocrine control of vertebrate reproductive cycles.

    PubMed

    Jones, Susan M

    2017-04-01

    Australian lizards exhibit a broad array of different reproductive strategies and provide an extraordinary diversity and range of models with which to address fundamental problems in reproductive biology. Studies on lizards have frequently led to new insights into hormonal regulatory pathways or mechanisms of control, but we have detailed knowledge of the reproductive cycle in only a small percentage of known species. This review provides an overview and synthesis of current knowledge of the hormonal control of reproductive cycles in Australian lizards. Agamid lizards have provided useful models with which to test hypotheses about the hormonal regulation of the expression of reproductive behaviors, while research on viviparous skinks is providing insights into the evolution of the endocrine control of gestation. However, in order to better understand the potential risks that environmental factors such as climate change and endocrine disrupting chemicals pose to our fauna, better knowledge is required of the fundamental characteristics of the reproductive cycle in a broader range of lizard species. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Deceleration of Fusion–Fission Cycles Improves Mitochondrial Quality Control during Aging

    PubMed Central

    Meyer-Hermann, Michael; Osiewacz, Heinz D.

    2012-01-01

    Mitochondrial dynamics and mitophagy play a key role in ensuring mitochondrial quality control. Impairment thereof was proposed to be causative to neurodegenerative diseases, diabetes, and cancer. Accumulation of mitochondrial dysfunction was further linked to aging. Here we applied a probabilistic modeling approach integrating our current knowledge on mitochondrial biology allowing us to simulate mitochondrial function and quality control during aging in silico. We demonstrate that cycles of fusion and fission and mitophagy indeed are essential for ensuring a high average quality of mitochondria, even under conditions in which random molecular damage is present. Prompted by earlier observations that mitochondrial fission itself can cause a partial drop in mitochondrial membrane potential, we tested the consequences of mitochondrial dynamics being harmful on its own. Next to directly impairing mitochondrial function, pre-existing molecular damage may be propagated and enhanced across the mitochondrial population by content mixing. In this situation, such an infection-like phenomenon impairs mitochondrial quality control progressively. However, when imposing an age-dependent deceleration of cycles of fusion and fission, we observe a delay in the loss of average quality of mitochondria. This provides a rational why fusion and fission rates are reduced during aging and why loss of a mitochondrial fission factor can extend life span in fungi. We propose the ‘mitochondrial infectious damage adaptation’ (MIDA) model according to which a deceleration of fusion–fission cycles reflects a systemic adaptation increasing life span. PMID:22761564

  17. Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle

    PubMed Central

    Catta-Preta, Carolina M. C.; Brum, Felipe L.; da Silva, Camila C.; Zuma, Aline A.; Elias, Maria C.; de Souza, Wanderley; Schenkman, Sergio; Motta, Maria Cristina M.

    2015-01-01

    Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number. PMID:26082757

  18. Modulation of the control of muscle sympathetic nerve activity during incremental leg cycling

    PubMed Central

    Ichinose, Masashi; Saito, Mitsuru; Fujii, Naoto; Ogawa, Takeshi; Hayashi, Keiji; Kondo, Narihiko; Nishiyasu, Takeshi

    2008-01-01

    We tested the hypotheses that arterial baroreflex (ABR) control over muscle sympathetic nerve activity (MSNA) in humans does not remain constant throughout a bout of leg cycling ranging in intensity from very mild to exhausting. ABR control over MSNA (burst incidence, burst strength and total MSNA) was evaluated by analysing the relationship between beat-to-beat spontaneous variations in diastolic arterial pressure (DAP) and MSNA in 15 healthy subjects at rest and during leg cycling in a seated position at five workloads: very mild (10 W), mild (82 ± 5.0 W), moderate (126 ± 10.2 W), heavy (156 ± 14.3 W), and exhausting (190 ± 21.2 W). The workload was incremented every 6 min. The linear relationships between DAP and MSNA variables were significantly shifted downward during very mild exercise, but then shifted progressively upward as exercise intensity increased. During heavy and exhausting exercise, moreover, the DAP–MSNA relationships were also significantly shifted rightward from the resting relationship. The sensitivity of ABR control over burst incidence and total MSNA was significantly lower during very mild exercise than during rest, and the sensitivity of the burst incidence control remained lower than the resting level at all higher exercise intensities. By contrast, the sensitivity of the total MSNA control recovered to the resting level during mild and moderate exercise, and was significantly increased during heavy and exhausting exercise (versus rest). We conclude that, in humans, ABR control over MSNA is not uniform throughout a leg cycling exercise protocol in which intensity was varied from very mild to exhausting. We suggest that this non-uniformity of ABR function is one of the mechanisms by which sympathetic and cardiovascular responses are matched to the exercise intensity. PMID:18403425

  19. Concepts for Life Cycle Cost Control Required to Achieve Space Transportation Affordability and Sustainability

    NASA Technical Reports Server (NTRS)

    Rhodes, Russel E.; Zapata, Edgar; Levack, Daniel J. H.; Robinson, John W.; Donahue, Benjamin B.

    2009-01-01

    Cost control must be implemented through the establishment of requirements and controlled continually by managing to these requirements. Cost control of the non-recurring side of life cycle cost has traditionally been implemented in both commercial and government programs. The government uses the budget process to implement this control. The commercial approach is to use a similar process of allocating the non-recurring cost to major elements of the program. This type of control generally manages through a work breakdown structure (WBS) by defining the major elements of the program. If the cost control is to be applied across the entire program life cycle cost (LCC), the approach must be addressed very differently. A functional breakdown structure (FBS) is defined and recommended. Use of a FBS provides the visibifity to allow the choice of an integrated solution reducing the cost of providing many different elements of like function. The different functional solutions that drive the hardware logistics, quantity of documentation, operational labor, reliability and maintainability balance, and total integration of the entire system from DDT&E through the life of the program must be fully defined, compared, and final decisions made among these competing solutions. The major drivers of recurring cost have been identified and are presented and discussed. The LCC requirements must be established and flowed down to provide control of LCC. This LCC control will require a structured rigid process similar to the one traditionally used to control weight/performance for space transportation systems throughout the entire program. It has been demonstrated over the last 30 years that without a firm requirement and methodically structured cost control, it is unlikely that affordable and sustainable space transportation system LCC will be achieved.

  20. Analysis of a Temperature-Controlled Exhaust Thermoelectric Generator During a Driving Cycle

    NASA Astrophysics Data System (ADS)

    Brito, F. P.; Alves, A.; Pires, J. M.; Martins, L. B.; Martins, J.; Oliveira, J.; Teixeira, J.; Goncalves, L. M.; Hall, M. J.

    2016-03-01

    Thermoelectric generators can be used in automotive exhaust energy recovery. As car engines operate under wide variable loads, it is a challenge to design a system for operating efficiently under these variable conditions. This means being able to avoid excessive thermal dilution under low engine loads and being able to operate under high load, high temperature events without the need to deflect the exhaust gases with bypass systems. The authors have previously proposed a thermoelectric generator (TEG) concept with temperature control based on the operating principle of the variable conductance heat pipe/thermosiphon. This strategy allows the TEG modules’ hot face to work under constant, optimized temperature. The variable engine load will only affect the number of modules exposed to the heat source, not the heat transfer temperature. This prevents module overheating under high engine loads and avoids thermal dilution under low engine loads. The present work assesses the merit of the aforementioned approach by analysing the generator output during driving cycles simulated with an energy model of a light vehicle. For the baseline evaporator and condenser configuration, the driving cycle averaged electrical power outputs were approximately 320 W and 550 W for the type-approval Worldwide harmonized light vehicles test procedure Class 3 driving cycle and for a real-world highway driving cycle, respectively.

  1. Control of cell-cycle-associated tetrahydrobiopterin synthesis in rat thymocytes.

    PubMed

    Schott, K; Brand, K; Hatakeyama, K; Kagamiyama, H; Maier, J; Werner, T; Ziegler, I

    1992-05-01

    The cell-cycle progression of rat thymocytes from G0 through G1 to DNA synthesis is associated with a transient synthesis of H4biopterin, the concentration of which reaches a maximum at the time of S-phase entry and then decreases. This synthesis of H4biopterin is controlled by the specific activity of GTP cyclohydrolase I, which peaks in G1/S cells. In contrast, the catalytic activity of sepiapterin reductase remains constant throughout the cell-cycle. At G0 the steady state mRNA levels specific for GTP cyclohydrolase I and sepiapterin reductase, respectively, are below the limits of detection. Both accumulate as the thymocytes progress through the cell-cycle but lack cyclic down regulation. The data indicate that the variations in H4biopterin synthesis during the cell-cycle are caused by growth regulated increase in GTP cyclohydrolase I mRNA expression, with subsequent post-translational inactivation. This latter is likely due to the degree of enzyme phosphorylation.

  2. Melatonin in the control of the estrous cycle of the Indian desert gerbil (Meriones hurrianae: Jerdon).

    PubMed

    Joshi, B N; Manepalli, S K; Saibaba, P

    1994-01-01

    Daily administration of melatonin for 8 weeks, either in the morning (9 a.m.) or late in the afternoon (5 p.m.), resulted in significant prolongation of the estrous cycle in the Indian desert gerbil Meriones hurrianae. The gonadosomatic index increased significantly (p < 0.01) in the melatonin-treated gerbils compared to the control animals. Histological study of the ovaries revealed enlargement of follicles and corpora lutea with hypertrophied granulosa cells in the melatonin-treated gerbils in comparison to their controls. The data suggest that the mechanism involved in the gonadal response to melatonin may not be the same in the temperate and tropical species.

  3. Rapid alterations of cell cycle control proteins in human T lymphocytes in microgravity

    PubMed Central

    2012-01-01

    In our study we aimed to identify rapidly reacting gravity-responsive mechanisms in mammalian cells in order to understand if and how altered gravity is translated into a cellular response. In a combination of experiments using "functional weightlessness" provided by 2D-clinostats and real microgravity provided by several parabolic flight campaigns and compared to in-flight-1g-controls, we identified rapid gravity-responsive reactions inside the cell cycle regulatory machinery of human T lymphocytes. In response to 2D clinorotation, we detected an enhanced expression of p21 Waf1/Cip1 protein within minutes, less cdc25C protein expression and enhanced Ser147-phosphorylation of cyclinB1 after CD3/CD28 stimulation. Additionally, during 2D clinorotation, Tyr-15-phosphorylation occurred later and was shorter than in the 1 g controls. In CD3/CD28-stimulated primary human T cells, mRNA expression of the cell cycle arrest protein p21 increased 4.1-fold after 20s real microgravity in primary CD4+ T cells and 2.9-fold in Jurkat T cells, compared to 1 g in-flight controls after CD3/CD28 stimulation. The histone acetyltransferase (HAT) inhibitor curcumin was able to abrogate microgravity-induced p21 mRNA expression, whereas expression was enhanced by a histone deacetylase (HDAC) inhibitor. Therefore, we suppose that cell cycle progression in human T lymphocytes requires Earth gravity and that the disturbed expression of cell cycle regulatory proteins could contribute to the breakdown of the human immune system in space. PMID:22273506

  4. Ecological controls on water-cycle response to climate variability in deserts

    PubMed Central

    Scanlon, B. R.; Levitt, D. G.; Reedy, R. C.; Keese, K. E.; Sully, M. J.

    2005-01-01

    The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Niño southern oscillation in the Mojave Desert. Extreme El Niño winter precipitation (2.3-2.5 times normal) typical of the U.S. Southwest would be expected to increase groundwater recharge, which is critical for water resources in semiarid and arid regions. However, lysimeter data indicate that rapid increases in vegetation productivity in response to elevated winter precipitation reduced soil water storage to half of that in a nonvegetated lysimeter, thereby precluding deep drainage below the root zone that would otherwise result in groundwater recharge. Vegetation dynamics have been controlling the water cycle in interdrainage desert areas throughout the U.S. Southwest, maintaining dry soil conditions and upward soil water flow since the last glacial period (10,000-15,000 yr ago), as shown by soil water chloride accumulations. Although measurements are specific to the U.S. Southwest, correlations between satellite-based vegetation productivity and elevated precipitation related to El Niño southern oscillation indicate this model may be applicable to desert basins globally. Understanding the two-way coupling between vegetation dynamics and the water cycle is critical for predicting how climate variability influences hydrology and water resources in water-limited landscapes. PMID:15837922

  5. Computational analysis of mammalian cell division gated by a circadian clock: quantized cell cycles and cell size control.

    PubMed

    Zámborszky, Judit; Hong, Christian I; Csikász Nagy, Attila

    2007-12-01

    Cell cycle and circadian rhythms are conserved from cyanobacteria to humans with robust cyclic features. Recently, molecular links between these two cyclic processes have been discovered. Core clock transcription factors, Bmal1 and Clock (Clk), directly regulate Wee1 kinase, which inhibits entry into the mitosis. We investigate the effect of this connection on the timing of mammalian cell cycle processes with computational modeling tools. We connect a minimal model of circadian rhythms, which consists of transcription-translation feedback loops, with a modified mammalian cell cycle model from Novak and Tyson (2004). As we vary the mass doubling time (MDT) of the cell cycle, stochastic simulations reveal quantized cell cycles when the activity of Wee1 is influenced by clock components. The quantized cell cycles disappear in the absence of coupling or when the strength of this link is reduced. More intriguingly, our simulations indicate that the circadian clock triggers critical size control in the mammalian cell cycle. A periodic brake on the cell cycle progress via Wee1 enforces size control when the MDT is quite different from the circadian period. No size control is observed in the absence of coupling. The issue of size control in the mammalian system is debatable, whereas it is well established in yeast. It is possible that the size control is more readily observed in cell lines that contain circadian rhythms, since not all cell types have a circadian clock. This would be analogous to an ultradian clock intertwined with quantized cell cycles (and possibly cell size control) in yeast. We present the first coupled model between the mammalian cell cycle and circadian rhythms that reveals quantized cell cycles and cell size control influenced by the clock.

  6. The primary cilium coordinates signaling pathways in cell cycle control and migration during development and tissue repair.

    PubMed

    Christensen, Søren T; Pedersen, Stine F; Satir, Peter; Veland, Iben R; Schneider, Linda

    2008-01-01

    Cell cycle control and migration are critical processes during development and maintenance of tissue functions. Recently, primary cilia were shown to take part in coordination of the signaling pathways that control these cellular processes in human health and disease. In this review, we present an overview of the function of primary cilia and the centrosome in the signaling pathways that regulate cell cycle control and migration with focus on ciliary signaling via platelet-derived growth factor receptor alpha (PDGFRalpha). We also consider how the primary cilium and the centrosome interact with the extracellular matrix, coordinate Wnt signaling, and modulate cytoskeletal changes that impinge on both cell cycle control and cell migration.

  7. Sub-cycle optical phase control of nanotunnelling in the single-electron regime

    NASA Astrophysics Data System (ADS)

    Rybka, Tobias; Ludwig, Markus; Schmalz, Michael F.; Knittel, Vanessa; Brida, Daniele; Leitenstorfer, Alfred

    2016-10-01

    The high peak electric fields provided by single-cycle light pulses can be harnessed to manipulate and control charge motion in solid-state systems, resulting in electron emission out of metals and semiconductors or high harmonics generation in dielectrics. These processes are of a non-perturbative character and require precise reproducibility of the electric-field profile. Here, we vary the carrier-envelope phase of 6-fs-long near-infrared pulses with pJ-level energy to control electronic transport in a laterally confined nanoantenna with an 8 nm gap. Peak current densities of 50 MA cm-2 are achieved, corresponding to the transfer of individual electrons in a half-cycle period of 2 fs. The observed behaviours are made possible by the strong distortion of the effective tunnelling barrier due to the extreme electric fields that the nanostructure provides and sustains under sub-cycle optical biasing. Operating at room temperature and in a standard atmosphere, the performed experiments demonstrate a robust class of nanoelectronic switches gated by phase-locked optical transients of minute energy content.

  8. Transcriptional Control of Cell-Cycle Quiescence During C. elegans Development

    PubMed Central

    Clayton, Joseph E.; van den Heuvel, Sander J.L.; Saito, R. Mako

    2008-01-01

    During the development of the C. elegans reproductive system, cells that give rise to the vulva, the vulval precursor cells (VPCs), remain quiescent for two larval stages before resuming cell division in the third larval stage. We have identified several transcriptional regulators that contribute to this temporary cell-cycle arrest. Mutation of lin-1 or lin-31, two downstream targets of the Receptor Tyrosine kinase (RTK)/Ras/MAP kinase cascade that controls VPC cell fate, disrupts the temporary VPC quiescence. We found that the LIN-1/Ets and LIN-31/FoxB transcription factors promote expression of CKI-1, a member of the p27 family of cyclin-dependent kinase inhibitors (CKIs). LIN-1 and LIN-31 promote cki-1/Kip-1 transcription prior to their inhibition through RTK/Ras/MAPK activation. Another mutation identified in the screen defined the mdt-13 TRAP240 Mediator subunit. Further analysis of the multisubunit Mediator complex revealed that a specific subset of its components act in VPC quiescence. These components substantially overlap with the CDK-8 module implicated in transcriptional repression. Taken together, strict control of cell-cycle quiescence during VPC development involves transcriptional induction of CKI-1 and transcriptional regulation through the Mediator complex. These transcriptional regulators represent potential molecular connections between development and the basic cell-cycle machinery. PMID:18082681

  9. p53 controls CDC7 levels to reinforce G1 cell cycle arrest upon genotoxic stress

    PubMed Central

    Tudzarova, Slavica; Dey, Ayona; Stoeber, Kai; Okorokov, Andrei L.; Williams, Gareth H.

    2016-01-01

    ABSTRACT DNA replication initiation is a key event in the cell cycle, which is dependent on 2 kinases - CDK2 and CDC7. Here we report a novel mechanism in which p53 induces G1 checkpoint and cell cycle arrest by downregulating CDC7 kinase in response to genotoxic stress. We demonstrate that p53 controls CDC7 stability post-transcriptionally via miR-192/215 and post-translationally via Fbxw7β E3 ubiquitin ligase. The p53-dependent pathway of CDC7 downregulation is interlinked with the p53-p21-CDK2 pathway, as p21-mediated inhibition of CDK2-dependent phosphorylation of CDC7 on Thr376 is required for GSK3ß-phosphorylation and Fbxw7ß-dependent degradation of CDC7. Notably, sustained oncogenic high levels of active CDC7 exert a negative feedback onto p53, leading to unrestrained S-phase progression and accumulation of DNA damage. Thus, p53-dependent control of CDC7 levels is essential for blocking G1/S cell-cycle transition upon genotoxic stress, thereby safeguarding the genome from instability and thus representing a novel general stress response. PMID:27611229

  10. Gait Cycle Driven Transmission Power Control Scheme for Wireless Body Area Network.

    PubMed

    Zang, Weilin; Li, Ye

    2017-03-28

    In wireless body area network (WBAN), walking movements can result in rapid channel fluctuations, which severely degrade the performance of transmission power control (TPC) schemes. On the other hand, these channel fluctuations are often periodic and are time-synchronized with the user's gait cycle, since they are all driven from the walking movements. In this paper, we propose a novel gait cycle driven transmission power control (G-TPC) for WBAN. The proposed G-TPC scheme reinforces the existing TPC scheme by exploiting the periodic channel fluctuation in the walking scenario. In the proposed scheme, the user's gait cycle information acquired by an accelerometer is used as beacons for arranging the transmissions at the time points with the ideal channel state. The specific transmission power is then determined by using received signal strength indication (RSSI). An experiment was conducted to evaluate the energy efficiency and reliability of the proposed G-TPC based on a CC2420 platform. The results reveal that compared to the original RL-TPC, G-TPC reduces energy consumption by 25% on the sensor node and reduce packet loss rate by 65%.

  11. Fiber-optic, anti-cycling, high pressure sodium street light control. Final technical progress report

    SciTech Connect

    1995-05-01

    This is the Final Technical Progress Report on a project to develop and market a Fiber-Optic Anti-Cycling High Pressure Sodium Street Light Control. The field test units are now being made with a single vertical PC board design and contains a computer-on-a-chip or PROM IC to take the place of the majority of the components previously contained on the upper logic board. This will reduce the final costs of the unit when it is in production and increase the control`s flexibility. The authors have finished the soft tooling and have made the 400 plastic cases for the field test units. The new configuration of the cases entails a simplified design of the control shell which will have the lenses cast in place. The shell and base plastics are now finished and in final assembly awaiting the completion of the PC boards.

  12. Controlling the duty cycle of the eigenstates in laser with multiple optical feedback.

    PubMed

    Zeng, Zhaoli; Zhang, Shulian; Tan, Yidong; Liu, Weixin

    2013-08-26

    The polarization dynamics of a quasi-isotropic single-mode laser subjected to multiple optical feedback is presented. The variable duty cycle of two eigenstates is observed in high-frequency optical fringes. The high-frequency optical fringes are induced by the multiple reflections in the asymmetry feedback cavity. The duty cycle of two eigenstates can be controlled easily by adjusting the position of polarization flipping due to the residual stress of laser mirror. Particularly, when the frequency difference results from residual stress is reduced to 1.5MHz, the position of polarization flipping moves to the edge of each fringe which can be used to measure small displacement with direction sensitivity and high resolution.

  13. Controlling the Motion of Electronic Wavepackets Using Cycle-Sculpted Two-Color Laser Fields

    NASA Astrophysics Data System (ADS)

    Kitzler, M.; Xie, X.; Roither, S.; Kartashov, D.; Baltuška, A.

    We use cycle-sculpted two-color waveforms to drive electronic wavepackets generated by strong-field ionization from helium, neon, and argon gas atoms and analyze their momentum spectra measured by electron-ion coincidence momentum spectroscopy. Varying the relative phase of the two colors allows to sculpt the ionizing field and hence to control the emission times and motion of the wavepackets on an attosecond timescale. Using semiclassical calculations, we investigate the influence of the ionic Coulomb field onto the motion of emitted electronic wavepackets. We further show that the measured electron momentum spectra contain interference patterns created by pairs of electron wavepackets that are released within a single laser-field cycle. We experimentally distinguish these subcycle interference structures from above-threshold ionization (ATI) peaks and argue that they can be used to extract the subcycle phase evolution of the laser-driven complex bound-state wavefunction.

  14. Cyclic fatigue analysis of rocket thrust chambers. Volume 2: Attitude control thruster high cycle fatigue

    NASA Technical Reports Server (NTRS)

    Miller, R. W.

    1974-01-01

    A finite element stress analysis was performed for the film cooled throat section of an attitude control thruster. The anlaysis employed the RETSCP finite element computer program. The analysis included thermal and pressure loads, and the effects of temperature dependent material properties, to determine the strain range corresponding to the thruster operating cycle. The configuration and operating conditions considered, correspond to a flightweight integrated thruster assembly which was thrust pulse tested. The computed strain range was used in conjuction with Haynes 188 Universal Slopes minimum life data to predict throat section fatigue life. The computed number of cycles to failure was greater than the number of pulses to which the thruster was experimentally subjected without failure.

  15. Is there a stratospheric pacemaker controlling the daily cycle of tropical rainfall?

    NASA Astrophysics Data System (ADS)

    Sakazaki, T.; Hamilton, K.; Zhang, C.; Wang, Y.

    2017-02-01

    Rainfall in the tropics exhibits a large, 12 h Sun-synchronous variation with coherent phase around the globe. A long-standing, but unproved, hypothesis for this phenomenon is excitation by the prominent 12 h atmospheric tide, which itself is significantly forced remotely by solar heating of the stratospheric ozone layer. We investigated the relative roles of large-scale tidal forcing and more local effects in accounting for the 12 h variation of tropical rainfall. A model of the atmosphere run with the diurnal cycle of solar heating artificially suppressed below the stratosphere still simulated a strong coherent 12 h rainfall variation ( 50% of control run), demonstrating that stratospherically forced atmospheric tide propagates downward to the troposphere and contributes to the organization of large-scale convection. The results have implications for theories of excitation of tropical atmospheric waves by moist convection, for the evaluation of climate models, and for explaining the recently discovered lunar tidal rainfall cycle.

  16. Phosphorylation of NDRG1 is temporally and spatially controlled during the cell cycle.

    PubMed

    McCaig, Catherine; Potter, Louisa; Abramczyk, Olga; Murray, James T

    2011-07-29

    The tumour metastasis suppressor, N-myc Downstream Regulated Gene (NDRG) 1, is a by the protein kinases SGK1 and GSK3β, but the relevance of its phosphorylation remains unclear. Analysis of HCT116 cells, either proficient or deficient for p53 revealed NDRG1 protein expression and phosphorylation by SGK1 was increased basally in p53-deficient cells. Treatment with the cell cycle inhibitors, aphidicolin or nocodazole also revealed increased NDRG1 phosphorylation in p53-deficient cells. Finally, phosphorylated NDRG1 was found to co-localise with γ-tubulin on centromeres and also to the cleavage furrow during cytokinesis. Taken together, this work demonstrates that NDRG1 phosphorylation, by the protein kinase SGK1, is temporally and spatially controlled during the cell cycle, suggesting a role for NDRG1 in successful mitosis.

  17. STK16 regulates actin dynamics to control Golgi organization and cell cycle

    PubMed Central

    Liu, Juanjuan; Yang, Xingxing; Li, Binhua; Wang, Junjun; Wang, Wenchao; Liu, Jing; Liu, Qingsong; Zhang, Xin

    2017-01-01

    STK16 is a ubiquitously expressed, myristoylated, and palmitoylated serine/threonine protein kinase with underexplored functions. Recently, it was shown to be involved in cell division but the mechanism remains unclear. Here we found that human STK16 localizes to the Golgi complex throughout the cell cycle and plays important roles in Golgi structure regulation. STK16 knockdown or kinase inhibition disrupts actin polymers and causes fragmented Golgi in cells. In vitro assays show that STK16 directly binds to actin and regulates actin dynamics in a concentration- and kinase activity-dependent way. In addition, STK16 knockdown or kinase inhibition not only delays mitotic entry and prolongs mitosis, but also causes prometaphase and cytokinesis arrest. Therefore, we revealed STK16 as a novel actin binding protein that resides in the Golgi, which regulates actin dynamics to control Golgi structure and participate in cell cycle progression. PMID:28294156

  18. Dissecting the fission yeast regulatory network reveals phase-specific control elements of its cell cycle.

    PubMed

    Bushel, Pierre R; Heard, Nicholas A; Gutman, Roee; Liu, Liwen; Peddada, Shyamal D; Pyne, Saumyadipta

    2009-09-16

    Fission yeast Schizosaccharomyces pombe and budding yeast Saccharomyces cerevisiae are among the original model organisms in the study of the cell-division cycle. Unlike budding yeast, no large-scale regulatory network has been constructed for fission yeast. It has only been partially characterized. As a result, important regulatory cascades in budding yeast have no known or complete counterpart in fission yeast. By integrating genome-wide data from multiple time course cell cycle microarray experiments we reconstructed a gene regulatory network. Based on the network, we discovered in addition to previously known regulatory hubs in M phase, a new putative regulatory hub in the form of the HMG box transcription factor SPBC19G7.04. Further, we inferred periodic activities of several less known transcription factors over the course of the cell cycle, identified over 500 putative regulatory targets and detected many new phase-specific and conserved cis-regulatory motifs. In particular, we show that SPBC19G7.04 has highly significant periodic activity that peaks in early M phase, which is coordinated with the late G2 activity of the forkhead transcription factor fkh2. Finally, using an enhanced Bayesian algorithm to co-cluster the expression data, we obtained 31 clusters of co-regulated genes 1) which constitute regulatory modules from different phases of the cell cycle, 2) whose phase order is coherent across the 10 time course experiments, and 3) which lead to identification of phase-specific control elements at both the transcriptional and post-transcriptional levels in S. pombe. In particular, the ribosome biogenesis clusters expressed in G2 phase reveal new, highly conserved RNA motifs. Using a systems-level analysis of the phase-specific nature of the S. pombe cell cycle gene regulation, we have provided new testable evidence for post-transcriptional regulation in the G2 phase of the fission yeast cell cycle. Based on this comprehensive gene regulatory network, we

  19. Cell Cycle Control by the Master Regulator CtrA in Sinorhizobium meliloti.

    PubMed

    Pini, Francesco; De Nisco, Nicole J; Ferri, Lorenzo; Penterman, Jon; Fioravanti, Antonella; Brilli, Matteo; Mengoni, Alessio; Bazzicalupo, Marco; Viollier, Patrick H; Walker, Graham C; Biondi, Emanuele G

    2015-05-01

    In all domains of life, proper regulation of the cell cycle is critical to coordinate genome replication, segregation and cell division. In some groups of bacteria, e.g. Alphaproteobacteria, tight regulation of the cell cycle is also necessary for the morphological and functional differentiation of cells. Sinorhizobium meliloti is an alphaproteobacterium that forms an economically and ecologically important nitrogen-fixing symbiosis with specific legume hosts. During this symbiosis S. meliloti undergoes an elaborate cellular differentiation within host root cells. The differentiation of S. meliloti results in massive amplification of the genome, cell branching and/or elongation, and loss of reproductive capacity. In Caulobacter crescentus, cellular differentiation is tightly linked to the cell cycle via the activity of the master regulator CtrA, and recent research in S. meliloti suggests that CtrA might also be key to cellular differentiation during symbiosis. However, the regulatory circuit driving cell cycle progression in S. meliloti is not well characterized in both the free-living and symbiotic state. Here, we investigated the regulation and function of CtrA in S. meliloti. We demonstrated that depletion of CtrA cause cell elongation, branching and genome amplification, similar to that observed in nitrogen-fixing bacteroids. We also showed that the cell cycle regulated proteolytic degradation of CtrA is essential in S. meliloti, suggesting a possible mechanism of CtrA depletion in differentiated bacteroids. Using a combination of ChIP-Seq and gene expression microarray analysis we found that although S. meliloti CtrA regulates similar processes as C. crescentus CtrA, it does so through different target genes. For example, our data suggest that CtrA does not control the expression of the Fts complex to control the timing of cell division during the cell cycle, but instead it negatively regulates the septum-inhibiting Min system. Our findings provide valuable

  20. From biological to lithological control of the B geochemical cycle in a forest watershed (Strengbach, Vosges)

    NASA Astrophysics Data System (ADS)

    Cividini, D.; Lemarchand, D.; Chabaux, F.; Boutin, R.; Pierret, M.-C.

    2010-06-01

    There is a fast growing interest in understanding the coupling between mineralogical and biological processes responsible for the migration of elements through continental ecosystems. This issue has fundamental impacts at the soil/plant scale because it can explain the tight links between soil and plant development and at the watershed scale because it gives a direct access to the water quality. In the present study, we performed an extended investigation of the bio-geochemical cycle of boron, which is an element known to be suitable for investigating water/rock interactions and vegetation cycling. New B data are provided along the hydro-bio-geochemical continuum in a forest ecosystem (Strengbach basin, Vosges, France), from rainwaters down to the outlet of the basin including systematic analyses of throughfalls, soil solutions, springs and brooks scattered in the watershed. At the watershed scale, we evidence a relationship between the B isotopic composition of river waters and the weathering regime outlining a predominant control of the parent rock mineralogy on the B geochemical behavior. At the soil/plant scale, it appears that the B geochemical cycle is controlled by the vegetation cycling, which is characterized by an uncommon, easy to distinguish, B isotopic composition (δ 11B ranging from about +30‰ to +45‰). Each year the amount of B being involved in the vegetation cycle is about four times greater than that of B being exported out of the watershed. At 10 cm depth in soil, where the plant roots are expected to be the most active, we observe a marked seasonal oscillation of the B isotopic values, which is interpreted as resulting from the vegetation activity. A mass balance calculation based on the assumption that that 10B is preferentially accumulated in the biomass tends to indicate that the soil/plant system does not behave at steady state with respect to B. Because of the very distinct B isotopic signature of vegetation and minerals in soil, box

  1. Controls of nitrogen cycling evaluated along a well-characterized climate gradient.

    PubMed

    von Sperber, Christian; Chadwick, Oliver A; Casciotti, Karen L; Peay, Kabir G; Francis, Christopher A; Kim, Amy E; Vitousek, Peter M

    2017-04-01

    The supply of nitrogen (N) constrains primary productivity in many ecosystems, raising the question "what controls the availability and cycling of N"? As a step toward answering this question, we evaluated N cycling processes and aspects of their regulation on a climate gradient on Kohala Volcano, Hawaii, USA. The gradient extends from sites receiving <300 mm/yr of rain to those receiving >3,000 mm/yr, and the pedology and dynamics of rock-derived nutrients in soils on the gradient are well understood. In particular, there is a soil process domain at intermediate rainfall within which ongoing weathering and biological uplift have enriched total and available pools of rock-derived nutrients substantially; sites at higher rainfall than this domain are acid and infertile as a consequence of depletion of rock-derived nutrients, while sites at lower rainfall are unproductive and subject to wind erosion. We found elevated rates of potential net N mineralization in the domain where rock-derived nutrients are enriched. Higher-rainfall sites have low rates of potential net N mineralization and high rates of microbial N immobilization, despite relatively high rates of gross N mineralization. Lower-rainfall sites have moderately low potential net N mineralization, relatively low rates of gross N mineralization, and rates of microbial N immobilization sufficient to sequester almost all the mineral N produced. Bulk soil δ(15) N also varied along the gradient, from +4‰ at high rainfall sites to +14‰ at low rainfall sites, indicating differences in the sources and dynamics of soil N. Our analysis shows that there is a strong association between N cycling and soil process domains that are defined using soil characteristics independent of N along this gradient, and that short-term controls of N cycling can be understood in terms of the supply of and demand for N.

  2. Oocyte maturation and cell cycle control: a farewell symposium for Pr Marcel Dorée.

    PubMed

    Prigent, Claude; Hunt, Tim

    2004-04-01

    Oocyte maturation and early development have been intensively studied for well over 100 years. The earliest theory proposed that after fertilisation and during cell division determinants were unequally distributed to control cell fate; experimental proof came from using frog eggs (Roux, 1888). After understanding the contribution of the nucleus and the chromosomes into cell cycle progression using sea urchin eggs (Boveri, 1902), it was the discovery of the cytoplasm contribution to the G2/M transition that led the cell cycle community in search of the "mitosis-inducing factor", MPF. Yoshio Masui was the first to experimentally demonstrate that few nanoliters of cytoplasm taken from a metaphase-arrested oocyte and microinjected in a G2-arrested oocyte was able to trigger the G2 to metaphase transition (Masui and Markert, 1971). Although the way to identify the mitotic factor seemed obvious, it proved very hard and was not purified until 1988 (Lohka et al, 1988), then work from a variety of organisms including Xenopus, starfish, clams, sea urchins and yeast converged on the identification of MPF as a complex of cdc2 and cyclin B (Dunphy et al, 1988; Gautier et al., 1988; Draetta et al., 1889; Meijer et al., 1989; Labbé et al., 1989; Gautier et al., 1990). Since then, the oocyte and egg extracts developed by Lohka and Masui have often been used to study cell cycle events such as nuclear envelop formation, chromatin condensation, DNA replication, repair, and recombination, Golgi formation, microtubule dynamics, spindle assembly, chromosome segregation as well as cell cycle controls.

  3. Geomorphic and substrate controls on spatial variability in river solute transport and biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jen; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

    2016-04-01

    Nutrient concentrations in surface waters and groundwaters are increasing in many agricultural catchments worldwide as a result of anthropogenic activities. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical transformation rates (e.g. denitrification) can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are not well understood. Here, we aimed to assess: 1) how differences in geomorphological heterogeneity control river solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive 'smart' tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small-scale targeted management interventions to alter geomorphic heterogeneity may be

  4. Effectiveness of Active Cycling in Subacute Stroke Rehabilitation: A Randomized Controlled Trial.

    PubMed

    Vanroy, Christel; Feys, Hilde; Swinnen, Anke; Vanlandewijck, Yves; Truijen, Steven; Vissers, Dirk; Michielsen, Marc; Wouters, Kristien; Cras, Patrick

    2017-08-01

    To examine the effects of 3 months of aerobic training (AT) followed by coaching on aerobic capacity, strength, and gait speed after subacute stroke. Randomized controlled trial. Inpatient rehabilitation center. Patients (N=59; mean age ± SD, 65.4±10.3y; 21 women (36%); Barthel Index ≤50 in 64% of patients) with first stroke and able to cycle at 50 revolutions/min were enrolled in the study 3 to 10 weeks after stroke onset. Patients were randomly allocated to a 3-month active cycling group (ACG, n=33) and education, or to a control group (CG, n=26). Afterward, patients in the ACG were randomly assigned either to a coaching (n=15) or to a noncoaching group (n=16) for 9 months. Aerobic capacity, isometric knee extension strength, and gait ability and speed were measured before and after intervention and during follow-up at 6 and 12 months. A nonsignificant difference was found in workload (Wattpeak) (P=.078) between ACG and CG after 3 months. Furthermore, after 3 months of cycling and after 9 months of coaching, all groups showed significant changes over time (P≤.027) in peak oxygen consumption, Wattpeak, leg strength, and gait speed. Also, significant changes over time (P<.001) were found in the ACG and the CG in patients with walking inability at baseline. No significant differences between training groups were found over time. Although our study did not have objective exercise data from the training device during follow-up, the 3-month active cycling (AC) program combined with education sessions seemed an applicable method in subacute stroke rehabilitation. New long-term AT interventions should focus on coaching approaches to facilitate training after a supervised AC program. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  5. Control Activity in Support of NASA Turbine Based Combined Cycle (TBCC) Research

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J.; Vrnak, Daniel R.; Le, Dzu K.; Ouzts, Peter J.

    2010-01-01

    Control research for a Turbine Based Combined Cycle (TBCC) propulsion system is the current focus of the Hypersonic Guidance, Navigation, and Control (GN&C) discipline team. The ongoing work at the NASA Glenn Research Center (GRC) supports the Hypersonic GN&C effort in developing tools to aid the design of control algorithms to manage a TBCC airbreathing propulsion system during a critical operating period. The critical operating period being addressed in this paper is the span when the propulsion system transitions from one cycle to another, referred to as mode transition. One such tool, that is a basic need for control system design activities, is computational models (hereto forth referred to as models) of the propulsion system. The models of interest for designing and testing controllers are Control Development Models (CDMs) and Control Validation Models (CVMs). CDMs and CVMs are needed for each of the following propulsion system elements: inlet, turbine engine, ram/scram dual-mode combustor, and nozzle. This paper presents an overall architecture for a TBCC propulsion system model that includes all of the propulsion system elements. Efforts are under way, focusing on one of the propulsion system elements, to develop CDMs and CVMs for a TBCC propulsion system inlet. The TBCC inlet aerodynamic design being modeled is that of the Combined-Cycle Engine (CCE) Testbed. The CCE Testbed is a large-scale model of an aerodynamic design that was verified in a small-scale screening experiment. The modeling approach includes employing existing state-of-the-art simulation codes, developing new dynamic simulations, and performing system identification experiments on the hardware in the NASA GRC 10 by10-Foot Supersonic Wind Tunnel. The developed CDMs and CVMs will be available for control studies prior to hardware buildup. The system identification experiments on the CCE Testbed will characterize the necessary dynamics to be represented in CDMs for control design. These

  6. Characterization and quenching of friction-induced limit cycles of electro-hydraulic servovalve control systems with transport delay.

    PubMed

    Wang, Yuan-Jay

    2010-10-01

    This paper develops a systematic and straightforward methodology to characterize and quench the friction-induced limit cycle conditions in electro-hydraulic servovalve control systems with transport delay in the transmission line. The nonlinear friction characteristic is linearized by using its corresponding describing function. The delay time in the transmission line, which could accelerate the generation of limit cycles is particularly considered. The stability equation method together with parameter plane method provides a useful tool for the establishment of necessary conditions to sustain a limit cycle directly in the constructed controller coefficient plane. Also, the stable region, the unstable region, and the limit cycle region are identified in the parameter plane. The parameter plane characterizes a clear relationship between limit cycle amplitude, frequency, transport delay, and the controller coefficients to be designed. The stability of the predicted limit cycle is checked by plotting stability curves. The stability of the system is examined when the viscous gain changes with respect to the temperature of the working fluid. A feasible stable region is characterized in the parameter plane to allow a flexible choice of controller gains. The robust prevention of limit cycle is achieved by selecting controller gains from the asymptotic stability region. The predicted results are verified by simulations. It is seen that the friction-induced limit cycles can be effectively predicted, removed, and quenched via the design of the compensator even in the case of viscous gain and delay time variations unconditionally.

  7. Rankine cycle condenser pressure control using an energy conversion device bypass valve

    DOEpatents

    Ernst, Timothy C; Nelson, Christopher R; Zigan, James A

    2014-04-01

    The disclosure provides a waste heat recovery system and method in which pressure in a Rankine cycle (RC) system of the WHR system is regulated by diverting working fluid from entering an inlet of an energy conversion device of the RC system. In the system, an inlet of a controllable bypass valve is fluidly coupled to a working fluid path upstream of an energy conversion device of the RC system, and an outlet of the bypass valve is fluidly coupled to the working fluid path upstream of the condenser of the RC system such that working fluid passing through the bypass valve bypasses the energy conversion device and increases the pressure in a condenser. A controller determines the temperature and pressure of the working fluid and controls the bypass valve to regulate pressure in the condenser.

  8. Analysis of Factors Controlling Cell Cycle that Can Be Synchronized Nondestructively During Root Cap Development

    SciTech Connect

    Hawes, Martha

    2011-02-04

    Publications and presentations during the final funding period, including progress in defining the substrate specificity, the primary goal of the project, are listed below. Both short-term and long-term responses mediated by PsUGT1 have been characterized in transgenic or mutant pea, alfalfa, and Arabidopsis with altered expression of PsUGT1. Additional progress includes evaluation of the relationship between control of the cell cycle by PsUGT1 and other glycosyltransferase and glycosidase enzymes that are co-regulated in the legume root cap during the onset of mitosis and differentiation. Transcriptional profiling and multidimensional protein identification technology ('MudPIT') have been used to establish the broader molecular context for the mechanism by which PsUGT1 controls cell cycle in response to environmental signals. A collaborative study with the Norwegian Forest Research Institute (who provided $10,000.00 in supplies and travel funds for collaborator Dr. Toril Eldhuset to travel to Arizona and Dr. H. H. Woo to travel to Norway) made it possible to establish that the inducible root cap system for studying carbohydrate synthesis and solubilization is expressed in gymnosperm as well as angiosperm species. This discovery provides an important tool to amplify the potential applications of the research in defining conserved cell cycle machinery across a very broad range of plant species and habitats. The final work, published during 2009, revealed an additional surprising parallel with mammalian immune responses: The cells whose production is controlled by PsUGT1 appear to function in a manner which is analogous to that of white blood cells, by trapping and killing in an extracellular manner. This may explain why mutation within the coding region of PsUGT1 and its homolog in humans (UGT1) is lethal to plants and animals. The work has been the subject of invited reviews. A postdoctoral fellow, eight undergraduate students, four M.S. students and three Ph

  9. Genetic variants in cell cycle control pathway confer susceptibility to aggressive prostate carcinoma.

    PubMed

    Kibel, Adam S; Ahn, Jiyoung; Isikbay, Masis; Klim, Aleksandra; Wu, William S; Hayes, Richard B; Isaacs, William B; Daw, E Warwick

    2016-04-01

    Because a significant number of patients with prostate cancer (PCa) are diagnosed with disease unlikely to cause harm, genetic markers associated with clinically aggressive PCa have potential clinical utility. Since cell cycle checkpoint dysregulation is crucial for the development and progression of cancer, we tested the hypothesis that common germ-line variants within cell cycle genes were associated with aggressive PCa. Via a two-stage design, 364 common sequence variants in 88 genes were tested. The initial stage consisted of 258 aggressive PCa patients and 442 controls, and the second stage added 384 aggressive PCa Patients and 463 controls. European-American and African-American samples were analyzed separately. In the first stage, SNPs were typed by Illumina Goldengate assay while in the second stage SNPs were typed by Pyrosequencing assays. Genotype frequencies between cases and controls were compared using logistical regression analysis with additive, dominant and recessive models. Eleven variants within 10 genes (CCNC, CCND3, CCNG1, CCNT2, CDK6, MDM2, SKP2, WEE1, YWHAB, YWHAH) in the European-American population and nine variants in 7 genes (CCNG1, CDK2, CDK5, MDM2, RB1, SMAD3, TERF2) in the African-American population were found to be associated with aggressive PCa using at least one model. Of particular interest, CCNC (rs3380812) was associated with risk in European-American cohorts from both institutions. CDK2 (rs1045435) and CDK5 (rs2069459) were associated with risk in the African-American cohorts from both institutions. Lastly, variants within MDM2 and CCNG1 were protective for aggressive PCa in both ethnic groups. This study confirms that polymorphisms within cell cycle genes are associated with clinically aggressive PCa. Validation of these markers in additional populations is necessary, but these markers may help identify patients at risk for potentially lethal carcinoma. © 2015 Wiley Periodicals, Inc.

  10. Menstrual Cycle Control in Female Astronauts and the Associated Risk of Venous Thromboembolism

    NASA Technical Reports Server (NTRS)

    Jain, Varsha; Wotring, Virginia

    2015-01-01

    Venous thromboembolism (VTE) is a common and serious condition affecting approximately 1-2 per 1000 people in the USA every year. There have been no documented case reports of VTE in female astronauts during spaceflight in the published literature. Some female astronauts use hormonal contraception to control their menstrual cycles and it is currently unknown how this affects their risk of VTE. Current terrestrial risk prediction models do not account for the spaceflight environment and the physiological changes associated with it. We therefore aim to estimate a specific risk score for female astronauts who are taking hormonal contraception for menstrual cycle control, to deduce whether they are at an elevated risk of VTE. A systematic review of the literature was conducted in order to identify and quantify known terrestrial risk factors for VTE. Studies involving analogues for the female astronaut population were also reviewed, for example, military personnel who use the oral contraceptive pill for menstrual suppression. Well known terrestrial risk factors, for example, obesity or smoking would not be applicable to our study population as these candidates would have been excluded during astronaut selection processes. Other risk factors for VTE include hormonal therapy, lower limb paralysis, physical inactivity, hyperhomocysteinemia, low methylfolate levels and minor injuries, all of which potentially apply to crew members LSAH data will be assessed to identify which of these risk factors are applicable to our astronaut population. Using known terrestrial risk data, an overall estimated risk of VTE for female astronauts using menstrual cycle control methods will therefore be calculated. We predict this will be higher than the general population but not significantly higher requiring thromboprophylaxis. This study attempts to delineate what is assumed to be true of our astronaut population, for example, they are known to be a healthy fit cohort of individuals, and

  11. Thermal Cycling of Thermal Control Paints on Carbon-Carbon and Carbon-Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.

    2006-01-01

    Carbon-carbon composites and carbon-polyimide composites are being considered for space radiator applications owing to their light weight and high thermal conductivity. For those radiator applications where sunlight will impinge on the surface, it will be necessary to apply a white thermal control paint to minimize solar absorptance and enhance infrared emittance. Several currently available white thermal control paints were applied to candidate carbon-carbon and carbon-polyimide composites and were subjected to vacuum thermal cycling in the range of -100 C to +277 C. The optical properties of solar absorptance and infrared emittance were evaluated before and after thermal cycling. In addition, adhesion of the paints was evaluated utilizing a tape test. The test matrix included three composites: resin-derived carbon-carbon and vapor infiltrated carbon-carbon, both reinforced with pitch-based P-120 graphite fibers, and a polyimide composite reinforced with T-650 carbon fibers, and three commercially available white thermal control paints: AZ-93, Z-93-C55, and YB-71P.

  12. Hypocretin/Orexin neuropeptides: participation in the control of sleep-wakefulness cycle and energy homeostasis.

    PubMed

    Nuñez, A; Rodrigo-Angulo, M L; Andrés, I De; Garzón, M

    2009-03-01

    Hypocretins or orexins (Hcrt/Orx) are hypothalamic neuropeptides that are synthesized by neurons located mainly in the perifornical area of the posterolateral hypothalamus. These hypothalamic neurons are the origin of an extensive and divergent projection system innervating numerous structures of the central nervous system. In recent years it has become clear that these neuropeptides are involved in the regulation of many organic functions, such as feeding, thermoregulation and neuroendocrine and cardiovascular control, as well as in the control of the sleep-wakefulness cycle. In this respect, Hcrt/Orx activate two subtypes of G protein-coupled receptors (Hcrt/Orx1R and Hcrt/Orx2R) that show a partly segregated and prominent distribution in neural structures involved in sleep-wakefulness regulation. Wakefulness-enhancing and/or sleep-suppressing actions of Hcrt/Orx have been reported in specific areas of the brainstem. Moreover, presently there are animal models of human narcolepsy consisting in modifications of Hcrt/Orx receptors or absence of these peptides. This strongly suggests that narcolepsy is the direct consequence of a hypofunction of the Hcrt/Orx system, which is most likely due to Hcrt/Orx neurons degeneration.The main focus of this review is to update and illustrate the available data on the actions of Hcrt/Orx neuropeptides with special interest in their participation in the control of the sleep-wakefulness cycle and the regulation of energy homeostasis. Current pharmacological treatment of narcolepsy is also discussed.

  13. Functional differentiation of SWI/SNF remodelers in transcription and cell cycle control.

    PubMed

    Moshkin, Yuri M; Mohrmann, Lisette; van Ijcken, Wilfred F J; Verrijzer, C Peter

    2007-01-01

    Drosophila BAP and PBAP represent two evolutionarily conserved subclasses of SWI/SNF chromatin remodelers. The two complexes share the same core subunits, including the BRM ATPase, but differ in a few signature subunits: OSA defines BAP, whereas Polybromo (PB) and BAP170 specify PBAP. Here, we present a comprehensive structure-function analysis of BAP and PBAP. An RNA interference knockdown survey revealed that the core subunits BRM and MOR are critical for the structural integrity of both complexes. Whole-genome expression profiling suggested that the SWI/SNF core complex is largely dysfunctional in cells. Regulation of the majority of target genes required the signature subunit OSA, PB, or BAP170, suggesting that SWI/SNF remodelers function mostly as holoenzymes. BAP and PBAP execute similar, independent, or antagonistic functions in transcription control and appear to direct mostly distinct biological processes. BAP, but not PBAP, is required for cell cycle progression through mitosis. Because in yeast the PBAP-homologous complex, RSC, controls cell cycle progression, our finding reveals a functional switch during evolution. BAP mediates G(2)/M transition through direct regulation of string/cdc25. Its signature subunit, OSA, is required for directing BAP to the string/cdc25 promoter. Our results suggest that the core subunits play architectural and enzymatic roles but that the signature subunits determine most of the functional specificity of SWI/SNF holoenzymes in general gene control.

  14. Water loss control using pressure management: life-cycle energy and air emission effects.

    PubMed

    Stokes, Jennifer R; Horvath, Arpad; Sturm, Reinhard

    2013-10-01

    Pressure management is one cost-effective and efficient strategy for controlling water distribution losses. This paper evaluates the life-cycle energy use and emissions for pressure management zones in Philadelphia, Pennsylvania, and Halifax, Nova Scotia. It compares water savings using fixed-outlet and flow-modulated pressure control to performance without pressure control, considering the embedded electricity and chemical consumption in the lost water, manufacture of pipe and fittings to repair breaks caused by excess pressure, and pressure management. The resulting energy and emissions savings are significant. The Philadelphia and Halifax utilities both avoid approximately 130 million liters in water losses annually using flow-modulated pressure management. The conserved energy was 780 GJ and 1900 GJ while avoided greenhouse gas emissions were 50 Mg and 170 Mg a year by Philadelphia and Halifax, respectively. The life-cycle financial and environmental performance of pressure management systems compares favorably to the traditional demand management strategy of installing low-flow toilets. The energy savings may also translate to cost-effective greenhouse gas emission reductions depending on the energy mix used, an important advantage in areas where water and energy are constrained and/or expensive and greenhouse gas emissions are regulated as in California, for example.

  15. Glucose-ABL1-TOR Signaling Modulates Cell Cycle Tuning to Control Terminal Appressorial Cell Differentiation.

    PubMed

    Marroquin-Guzman, Margarita; Sun, Guangchao; Wilson, Richard A

    2017-01-01

    The conserved target of rapamycin (TOR) pathway integrates growth and development with available nutrients, but how cellular glucose controls TOR function and signaling is poorly understood. Here, we provide functional evidence from the devastating rice blast fungus Magnaporthe oryzae that glucose can mediate TOR activity via the product of a novel carbon-responsive gene, ABL1, in order to tune cell cycle progression during infection-related development. Under nutrient-free conditions, wild type (WT) M. oryzae strains form terminal plant-infecting cells (appressoria) at the tips of germ tubes emerging from three-celled spores (conidia). WT appressorial development is accompanied by one round of mitosis followed by autophagic cell death of the conidium. In contrast, Δabl1 mutant strains undergo multiple rounds of accelerated mitosis in elongated germ tubes, produce few appressoria, and are abolished for autophagy. Treating WT spores with glucose or 2-deoxyglucose phenocopied Δabl1. Inactivating TOR in Δabl1 mutants or glucose-treated WT strains restored appressorium formation by promoting mitotic arrest at G1/G0 via an appressorium- and autophagy-inducing cell cycle delay at G2/M. Collectively, this work uncovers a novel glucose-ABL1-TOR signaling axis and shows it engages two metabolic checkpoints in order to modulate cell cycle tuning and mediate terminal appressorial cell differentiation. We thus provide new molecular insights into TOR regulation and cell development in response to glucose.

  16. Glucose-ABL1-TOR Signaling Modulates Cell Cycle Tuning to Control Terminal Appressorial Cell Differentiation

    PubMed Central

    2017-01-01

    The conserved target of rapamycin (TOR) pathway integrates growth and development with available nutrients, but how cellular glucose controls TOR function and signaling is poorly understood. Here, we provide functional evidence from the devastating rice blast fungus Magnaporthe oryzae that glucose can mediate TOR activity via the product of a novel carbon-responsive gene, ABL1, in order to tune cell cycle progression during infection-related development. Under nutrient-free conditions, wild type (WT) M. oryzae strains form terminal plant-infecting cells (appressoria) at the tips of germ tubes emerging from three-celled spores (conidia). WT appressorial development is accompanied by one round of mitosis followed by autophagic cell death of the conidium. In contrast, Δabl1 mutant strains undergo multiple rounds of accelerated mitosis in elongated germ tubes, produce few appressoria, and are abolished for autophagy. Treating WT spores with glucose or 2-deoxyglucose phenocopied Δabl1. Inactivating TOR in Δabl1 mutants or glucose-treated WT strains restored appressorium formation by promoting mitotic arrest at G1/G0 via an appressorium- and autophagy-inducing cell cycle delay at G2/M. Collectively, this work uncovers a novel glucose-ABL1-TOR signaling axis and shows it engages two metabolic checkpoints in order to modulate cell cycle tuning and mediate terminal appressorial cell differentiation. We thus provide new molecular insights into TOR regulation and cell development in response to glucose. PMID:28072818

  17. Neutron Production from Feedback Controlled Thermal Cycling of a Pyroelectric Crystal Stack

    SciTech Connect

    Tang, V; Meyer, G; Schmid, G; Spadaccini, C; Kerr, P; Rusnak, B; Sampayan, S; Naranjo, B; Putterman, S

    2007-08-09

    The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of {approx}10 nA and neutron output of 1.9 ({+-}0.3) x 10{sup 5} per thermal cycle using a crystal heating rate of 0.2 C/s from 10 C to 110 C. A 3 cm diameter by 1 cm thick LiTaO{sub 3} crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D-D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.

  18. Pleiotropy in the wild: the dormancy gene DOG1 exerts cascading control on life cycles.

    PubMed

    Chiang, George C K; Barua, Deepak; Dittmar, Emily; Kramer, Elena M; de Casas, Rafael Rubio; Donohue, Kathleen

    2013-03-01

    In the wild, organismal life cycles occur within seasonal cycles, so shifts in the timing of developmental transitions can alter the seasonal environment experienced subsequently. Effects of genes that control the timing of prior developmental events can therefore be magnified in the wild because they determine seasonal conditions experienced by subsequent life stages, which can influence subsequent phenotypic expression. We examined such environmentally induced pleiotropy of developmental-timing genes in a field experiment with Arabidopsis thaliana. When studied in the field under natural seasonal variation, an A. thaliana seed-dormancy gene, Delay Of Germination 1 (DOG1), was found to influence not only germination, but also flowering time, overall life history, and fitness. Flowering time of the previous generation, in turn, imposed maternal effects that altered germination, the effects of DOG1 alleles, and the direction of natural selection on these alleles. Thus under natural conditions, germination genes act as flowering genes and potentially vice versa. These results illustrate how seasonal environmental variation can alter pleiotropic effects of developmental-timing genes, such that effects of genes that regulate prior life stages ramify to influence subsequent life stages. In this case, one gene acting at the seed stage impacted the entire life cycle.

  19. Neutron production from feedback controlled thermal cycling of a pyroelectric crystal

    SciTech Connect

    Tang, V.; Meyer, G.; Morse, J.; Schmid, G.; Spadaccini, C.; Kerr, P.; Rusnak, B.; Sampayan, S.; Naranjo, B.; Putterman, S.

    2007-12-15

    The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of {approx}10 nA and neutron output of 1.9({+-}0.3)x10{sup 5} per thermal cycle using a crystal heating rate of 0.2 deg. C/s from 10 to 110 deg. C. A 3 cm diameter by 1 cm thick LiTaO{sub 3} crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D-D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.

  20. Neutron production from feedback controlled thermal cycling of a pyroelectric crystal.

    PubMed

    Tang, V; Meyer, G; Morse, J; Schmid, G; Spadaccini, C; Kerr, P; Rusnak, B; Sampayan, S; Naranjo, B; Putterman, S

    2007-12-01

    The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of approximately 10 nA and neutron output of 1.9(+/-0.3)x10(5) per thermal cycle using a crystal heating rate of 0.2 degrees C/s from 10 to 110 degrees C. A 3 cm diameter by 1 cm thick LiTaO(3) crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D-D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.

  1. The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control

    SciTech Connect

    Yang, Yunfeng; McCue, Lee Ann; Parsons, Andrea; Feng, Sheng; Zhou, Jizhong

    2010-01-01

    Background: It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. It is unclear in the g-proteobacterium S. oneidensis whether TCA is also regulated by Fur and RyhB. Results: In the present study, we showed that a fur deletion mutant of S. oneidensis could utilize TCA compounds. Consistently, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and experimentally demonstrated the gene expression. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB. Conclusions: These cumulative results delineate an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other g-proteobacteria. This work represents a step forward for understanding the unique regulation in S. oneidensis.

  2. The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control

    SciTech Connect

    Yang, Yunfeng; McCue, Lee Ann; Parsons, Andrea B.; Feng, Sheng; Zhou, Jizhong

    2010-10-26

    It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. In this study, we showed that a fur deletion mutant of the γ-proteobacterium S. oneidensis could utilize TCA compounds. In addition, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and demonstrated its expression experimentally. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB. This work delineates an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other γ-proteobacteria.

  3. Demand Controlled Economizer Cycles: A Direct Digital Control Scheme for Heating, Ventilating, and Air Conditioning Systems,

    DTIC Science & Technology

    1984-05-01

    includes a heating coil and thermostatic control to maintain the air in this path at an elevated temperature, typically around 80 degrees Farenheit (80 F...1238 Aug 1 1236 1237 52 1074 1126 50 1033 1083 Sep 8 8 5W 862 7T 600 678 75 603 7r Oct 51 400 451 119 204 323 115 207 322 ov 64 123 287 187 71 258

  4. Classical linear-control analysis applied to business-cycle dynamics and stability

    NASA Technical Reports Server (NTRS)

    Wingrove, R. C.

    1983-01-01

    Linear control analysis is applied as an aid in understanding the fluctuations of business cycles in the past, and to examine monetary policies that might improve stabilization. The analysis shows how different policies change the frequency and damping of the economic system dynamics, and how they modify the amplitude of the fluctuations that are caused by random disturbances. Examples are used to show how policy feedbacks and policy lags can be incorporated, and how different monetary strategies for stabilization can be analytically compared. Representative numerical results are used to illustrate the main points.

  5. Global control of cell growth in fission yeast and its coordination with the cell cycle.

    PubMed

    Navarro, Francisco J; Weston, Louise; Nurse, Paul

    2012-12-01

    Cell growth is a fundamental process for every cell but its pleiotropic complexity makes it difficult to comprehend. Global aspects of cellular growth, like the overall determinants of growth rate are not well understood. Here we examine the cell growth pattern of the fission yeast Schizosaccharomyces pombe during the mitotic and meiotic cell cycles. We also explore recent findings illuminating aspects of cell size homeostasis and cell growth regulation, and propose that there are global controls over growth acting at the level of the cell. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. Spermatogenic Cycle and Steroidogenic Control of Spermatogenesis in Mytilus galloprovincialis Collected in the Bay of Naples.

    PubMed

    Prisco, Marina; Agnese, Marisa; De Marino, Adriano; Andreuccetti, Piero; Rosati, Luigi

    2017-10-01

    The aim of the present article was to study the spermatogenic cycle of Mytilus galloprovincialis collected in the Bay of Naples during a whole year and to acquire new insights into the mechanism of control. Knowledge of the Mytilus cycle in this geographic area is of particular interest as, to the best of our knowledge, the male gonad cycle has been hitherto unexplored. Testis organization was evaluated together with the localization of the enzymes 3β-HSD, 17β-HSD, and P450-aromatase, which are strictly connected to the synthesis of two key hormones involved in the testis activity: testosterone and 17β-estradiol. It was demonstrated that: (1) the spermatogenic cycle starts in late Summer-early Fall and continues until early Winter, when the first spawning occurs; after rapid gonad restoration, several spawning events take place until June, when the testis becomes non-active again; (2) in the testis, true Leydig and Sertoli cells are present; (3) during the reproductive period, Sertoli, Leydig, germ, and adipogranular cells (ADGs) are positive to 3β-HSD and 17β-HSD, while only germ cells are positive to P450 aromatase; by contrast, during the resting period, only ADGs are positive to 3β-HSD and 17β-HSD, and P450-aromatase is no longer recognizable. The presence of a hermaphrodite sample is also described. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1881-1894, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  7. Live birth rates after combined adjuvant therapy in IVF-ICSI cycles: a matched case-control study.

    PubMed

    Motteram, C; Vollenhoven, B; Hope, N; Osianlis, T; Rombauts, L J

    2015-04-01

    The effectiveness of combined co-treatment with aspirin, doxycycline, prednisolone, with or without oestradiol patches, was investigated on live birth (LBR) rates after fresh and frozen embryo transfers (FET) in IVF and intracytoplasmic sperm injection cycles. Cases (n = 485) and controls (n = 485) were extensively matched in a one-to-one ratio on nine physical and clinical parameters: maternal age, body mass index, smoking status, stimulation cycle number, cumulative dose of FSH, stimulation protocol, insemination method, day of embryo transfer and number of embryos transferred. No significant differences were found in fresh cycles between cases and controls for the pregnancy outcomes analysed, but fewer surplus embryos were available for freezing in the combined adjuvant group. In FET cycles, LBR was lower in the treatment group (OR: 0.49, 95% CI 0.25 to 0.95). The lower LBR in FET cycles seemed to be clustered in patients receiving combined adjuvant treatment without luteal oestradiol (OR 0.37, 95% CI 0.17 to 0.80). No difference was found in LBR between cases and controls when stratified according to the number of previous cycles (<3 or ≥3). There is no benefit of this combined adjuvant strategy in fresh IVF cycles, and possible harm when used in frozen cycles.

  8. Abiotic versus biotic controls on soil nitrogen cycling in drylands along a 3200 km transect

    NASA Astrophysics Data System (ADS)

    Liu, Dongwei; Zhu, Weixing; Wang, Xiaobo; Pan, Yuepeng; Wang, Chao; Xi, Dan; Bai, Edith; Wang, Yuesi; Han, Xingguo; Fang, Yunting

    2017-03-01

    Nitrogen (N) cycling in drylands under changing climate is not well understood. Our understanding of N cycling over larger scales to date relies heavily on the measurement of bulk soil N, and the information about internal soil N transformations remains limited. The 15N natural abundance (δ15N) of ammonium and nitrate can serve as a proxy record for the N processes in soils. To better understand the patterns and mechanisms of N cycling in drylands, we collected soils along a 3200 km transect at about 100 km intervals in northern China, with mean annual precipitation (MAP) ranging from 36 to 436 mm. We analyzed N pools and δ15N of ammonium, dual isotopes (15N and 18O) of nitrate, and the microbial gene abundance associated with soil N transformations. We found that N status and its driving factors were different above and below a MAP threshold of 100 mm. In the arid zone with MAP below 100 mm, soil inorganic N accumulated, with a large fraction being of atmospheric origin, and ammonia volatilization was strong in soils with high pH. In addition, the abundance of microbial genes associated with soil N transformations was low. In the semiarid zone with MAP above 100 mm, soil inorganic N concentrations were low and were controlled mainly by biological processes (e.g., plant uptake and denitrification). The preference for soil ammonium over nitrate by the dominant plant species may enhance the possibility of soil nitrate losses via denitrification. Overall, our study suggests that a shift from abiotic to biotic controls on soil N biogeochemistry under global climate changes would greatly affect N losses, soil N availability, and other N transformation processes in these drylands in China.

  9. Diurnal cycles control the fate of contaminants at an Andean river confluence impacted by legacy mining

    NASA Astrophysics Data System (ADS)

    Pasten, P.; Guerra, P. A.; Simonson, K.; Bonilla, C.; Pizarro, G. E.; Escauriaza, C. R.; González, C.

    2014-12-01

    The importance of hydrologic-geochemical interactions in arid environments is a controlling factor in quality and quantity of water available for human consumption and agriculture. When acid drainage affects these watersheds, water quality is gravely degraded. Despite its effect on watersheds, the relationship between time changes in hydrological variables and water quality in arid regions has not been studied thoroughly. Temporal variations in acid drainage can control when the transport of toxic elements is increased. We performed field work at the Azufre River (pH 2, E.C~10.9 mS/cm) and Caracarani River (pH 8.7, E.C~1.2 mS/cm) confluence, located in the Northern Chilean Altiplano (at 4000 m asl). We registered stream flowrates (total flowrate~430 L/s), temperature and electric conductivity (E.C) hourly using in-stream data loggers during one year. We also measured turbidity and pH during one field survey at different distances from the junction, as a proxy of the formation of iron-aluminum particles that cycle trace elements in these environments. We found turbidity-pH diurnal cycles were caused by upstream hourly changes in upstream flowrate: when the Caracarani River flowrate reached its daily peak, particle formation occurred, while the dissolution of particles occurred when the Azufre River reached its maximum value. This last process occurred due to upstream freeze-thaw cycles. This study shows how the dynamics of natural confluences determines chemical transport. The formation of particles enriched in toxic elements can promote settling as a natural attenuation process, while their dissolution will produce their release and transport long distances downstream. It is important to consider time as an important variable in water quality monitoring and in water management infrastructure where pulses of contamination can have potentially negative effects in its use. Acknowledgements: Funding was provided by "Proyecto Fondecyt 1130936" and "CONICYT

  10. Molecular mechanisms of cell cycle control in the mouse Y1 adrenal cell line.

    PubMed

    Costa, Erico T; Forti, Fábio L; Rocha, Kátia M; Moraes, Miriam S; Armelin, Hugo A

    2004-11-01

    Y1 adrenocortical tumor cells possess amplified and overexpressed c-Ki-ras proto-oncogene, displaying chronic high levels of the c-Ki-Ras-GTP protein. Despite this oncogenic lesion, we previously reported that Y1 cells retain tight regulatory mechanisms of cell cycle control typified by the mitogenic response triggered by FGF2 in G0/G1-arrested cells. ACTH, on the other hand, elicits cAMP/PKA-mediated antimitogenic mechanisms involving Akt/PKB dephosphorylation/deactivation and c-Myc protein degradation, blocking G1 phase progression stimulated by FGF2. In this paper we report that ACTH does not directly antagonize any of the early or late sequential steps comprising the mitogenic response triggered by FGF2. In effect, ACTH targets deactivation of constitutively phosphorylated-Akt, restraining the potential of c-Ki-Ras-GTP to subvert Y1 cell cycle control. Thus, we can consider ACTH a tumor suppressor rather than an antimitogenic hormone. In addition, we present initial results showing that high constitutive levels of c-Ki-Ras-GTP render Y1 cells susceptible to dye upon FGF2 treatment. This surprising FGF2 death-effect, that is independent of the well known FGF2-mitogenic activity, might involve a natural unsuspected mechanism for restraining oncogene-induced proliferation.

  11. The plant cell cycle: Pre-Replication complex formation and controls.

    PubMed

    Brasil, Juliana Nogueira; Costa, Carinne N Monteiro; Cabral, Luiz Mors; Ferreira, Paulo C G; Hemerly, Adriana S

    2017-03-16

    The multiplication of cells in all living organisms requires a tight regulation of DNA replication. Several mechanisms take place to ensure that the DNA is replicated faithfully and just once per cell cycle in order to originate through mitoses two new daughter cells that contain exactly the same information from the previous one. A key control mechanism that occurs before cells enter S phase is the formation of a pre-replication complex (pre-RC) that is assembled at replication origins by the sequential association of the origin recognition complex, followed by Cdt1, Cdc6 and finally MCMs, licensing DNA to start replication. The identification of pre-RC members in all animal and plant species shows that this complex is conserved in eukaryotes and, more importantly, the differences between kingdoms might reflect their divergence in strategies on cell cycle regulation, as it must be integrated and adapted to the niche, ecosystem, and the organism peculiarities. Here, we provide an overview of the knowledge generated so far on the formation and the developmental controls of the pre-RC mechanism in plants, analyzing some particular aspects in comparison to other eukaryotes.

  12. The plant cell cycle: Pre-Replication complex formation and controls

    PubMed Central

    Brasil, Juliana Nogueira; Costa, Carinne N. Monteiro; Cabral, Luiz Mors; Ferreira, Paulo C. G.; Hemerly, Adriana S.

    2017-01-01

    Abstract The multiplication of cells in all living organisms requires a tight regulation of DNA replication. Several mechanisms take place to ensure that the DNA is replicated faithfully and just once per cell cycle in order to originate through mitoses two new daughter cells that contain exactly the same information from the previous one. A key control mechanism that occurs before cells enter S phase is the formation of a pre-replication complex (pre-RC) that is assembled at replication origins by the sequential association of the origin recognition complex, followed by Cdt1, Cdc6 and finally MCMs, licensing DNA to start replication. The identification of pre-RC members in all animal and plant species shows that this complex is conserved in eukaryotes and, more importantly, the differences between kingdoms might reflect their divergence in strategies on cell cycle regulation, as it must be integrated and adapted to the niche, ecosystem, and the organism peculiarities. Here, we provide an overview of the knowledge generated so far on the formation and the developmental controls of the pre-RC mechanism in plants, analyzing some particular aspects in comparison to other eukaryotes. PMID:28304073

  13. The Homeodomain Iroquois Proteins Control Cell Cycle Progression and Regulate the Size of Developmental Fields.

    PubMed

    Barrios, Natalia; González-Pérez, Esther; Hernández, Rosario; Campuzano, Sonsoles

    2015-08-01

    During development, proper differentiation and final organ size rely on the control of territorial specification and cell proliferation. Although many regulators of these processes have been identified, how both are coordinated remains largely unknown. The homeodomain Iroquois/Irx proteins play a key, evolutionarily conserved, role in territorial specification. Here we show that in the imaginal discs, reduced function of Iroquois genes promotes cell proliferation by accelerating the G1 to S transition. Conversely, their increased expression causes cell-cycle arrest, down-regulating the activity of the Cyclin E/Cdk2 complex. We demonstrate that physical interaction of the Iroquois protein Caupolican with Cyclin E-containing protein complexes, through its IRO box and Cyclin-binding domains, underlies its activity in cell-cycle control. Thus, Drosophila Iroquois proteins are able to regulate cell-autonomously the growth of the territories they specify. Moreover, our results provide a molecular mechanism for a role of Iroquois/Irx genes as tumour suppressors.

  14. Study of Room Temperature and Humidity Control Method on Dehumidification System Reheated by Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroo; Funakoshi, Sunao; Yokoyama, Hidenori; Morimoto, Motoo; Saito, Kiyoshi

    The new ways to control the humidity and the temperature of the room accurately during the dehumidification operation reheated by refrigeration cycle on room air conditioners using R 410A was investigated. The indoor heat exchanger is divided into a condensing part and an evaporating part by a dehumidification valve which is located between these two heat exchangers. The indoor air cooled and dehumidified by the evaporating part is heated by the condensing part. The dehumidification capacity increased according to increasing the compressor rotational speed. And the reheating capacity increased according to decreasing the outdoor fan rotational speed. So the humidity and the temperature of the room was controlled to the setting values exactly by regulating the compressor rotational speed and the outdoor fan rotational speed alternately.

  15. p53 functions as a cell cycle control protein in osteosarcomas.

    PubMed Central

    Diller, L; Kassel, J; Nelson, C E; Gryka, M A; Litwak, G; Gebhardt, M; Bressac, B; Ozturk, M; Baker, S J; Vogelstein, B

    1990-01-01

    Mutations in the p53 gene have been associated with a wide range of human tumors, including osteosarcomas. Although it has been shown that wild-type p53 can block the ability of E1a and ras to cotransform primary rodent cells, it is poorly understood why inactivation of the p53 gene is important for tumor formation. We show that overexpression of the gene encoding wild-type p53 blocks the growth of osteosarcoma cells. The growth arrest was determined to be due to an inability of the transfected cells to progress into S phase. This suggests that the role of the p53 gene as an antioncogene may be in controlling the cell cycle in a fashion analogous to the check-point control genes in Saccharomyces cerevisiae. Images PMID:2233717

  16. p53 functions as a cell cycle control protein in osteosarcomas.

    PubMed

    Diller, L; Kassel, J; Nelson, C E; Gryka, M A; Litwak, G; Gebhardt, M; Bressac, B; Ozturk, M; Baker, S J; Vogelstein, B

    1990-11-01

    Mutations in the p53 gene have been associated with a wide range of human tumors, including osteosarcomas. Although it has been shown that wild-type p53 can block the ability of E1a and ras to cotransform primary rodent cells, it is poorly understood why inactivation of the p53 gene is important for tumor formation. We show that overexpression of the gene encoding wild-type p53 blocks the growth of osteosarcoma cells. The growth arrest was determined to be due to an inability of the transfected cells to progress into S phase. This suggests that the role of the p53 gene as an antioncogene may be in controlling the cell cycle in a fashion analogous to the check-point control genes in Saccharomyces cerevisiae.

  17. Adaptive Control of Fast-Scale Bifurcation in Peak Current Controlled Buck-Boost Inverter via One-Cycle Compensation

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Dong, Shuai; Guan, Weimin; Yi, Chuanzhi; He, Bo

    In this paper, one-cycle compensation (OCC) method is proposed to realize adaptive control of fast-scale bifurcation in the peak current controlled buck-boost inverter because the proposed control method can adjust the slope of the integrator’s output voltage automatically through extracting a sinusoidal signal from the absolute value of the reference voltage. In order to reveal their underlying mechanisms of fast-scale bifurcations, a modified averaged model which can capture the sample-and-hold effect is derived in detail to describe the fast-scale dynamics of the buck-boost inverter. Based on the proposed model, a theoretical analysis is performed to identify both the fast-scale period-doubling bifurcation and the fast-scale Hopf one by judging in what way the poles loci move. It has been shown that the OCC method can be used not only to discover the unknown dynamical behaviors (i.e. fast-scale Hopf bifurcation), but also to enlarge the stable region in peak current controlled buck-boost inverter. In addition, the critical bifurcation angles and the parameter behavior boundary are given to verify the effectiveness of the adaptive bifurcation control method. Finally, PSpice circuit experiments are performed to verify the above theoretical and numerical results.

  18. Rates and environmental controls of sediment N and S cycles in diverse aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Gu, C.; Pallud, C. E.

    2010-12-01

    Chuanhui Gu and Celine Pallud Recent studies of coupled NO3- driven SO42- production found chemolithoautotrophic bacterial metabolism may remove NO3- by coupling its reduction with the oxidation of reduced S to SO42-. The objectives of this study were to investigate the magnitude and interaction of NO3- and SO42- metabolic rates (e.g. nitrate reduction rate, ammonium production rate, sulfate production rate, and sulfate reduction rate, etc) across diverse freshwater, saline, and hypersaline water systems. Metabolic rates of major N and S cycles were measured on intact sediment cores using flow through reactors. Single TEA (i.e.NO3- or SO42-) addition and simultaneous TEAs addition caused a variety of responses in the N and S metabolic rates. We used a multivariate statistics tool, redundancy analysis, to access how environmental factors might control the variability of these metabolic rates. Our analysis showed pH, overlying water SO42- concentration, and salinity were three dominant environmental factors that control the N and S metabolic rates. The three factors combined explained 62% of variance of the metabolic rates. When NO3- and SO42- were both present, however, sediment As content, grain size, and N content determined the variability of the metabolic rates. These three factors together accounted for 58% of total variance of the metabolic rates. The different sets of environmental controls over the N and S metabolic rates under single TEA vs. two TEA conditions indicate the interior coupling between N and S cycles. These results showed there is no single set of environmental variables that can be used to predict the spatial variability of N and S metabolic rates, and controls on N processing in landscape subject to S and N pollution are more complex than previously appreciated.

  19. Endogenous and exogenous control of ecosystem function: N cycling in headwater streams.

    PubMed

    Valett, H M; Thomas, S A; Mulholland, P J; Webster, J R; Dahm, C N; Fellows, C S; Crenshaw, C L; Peterson, C G

    2008-12-01

    Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of 15N as nitrate in six streams differing in riparian-stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in 15N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; microg N x m(-2) x s(-1)) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (v(f); mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.

  20. Lithium isotopes in speleothems: Temperature-controlled variation in silicate weathering during glacial cycles

    NASA Astrophysics Data System (ADS)

    Pogge von Strandmann, Philip A. E.; Vaks, Anton; Bar-Matthews, Miryam; Ayalon, Avner; Jacob, Ezekiel; Henderson, Gideon M.

    2017-07-01

    Terrestrial chemical weathering of silicate minerals is a fundamental component of the global cycle of carbon and other elements. Past changes in temperature, rainfall, ice cover, sea-level and physical erosion are thought to affect weathering but the relative impact of these controls through time remains poorly constrained. This problem could be addressed if the nature of past weathering could be constrained at individual sites. In this study, we investigate the use of speleothems as local recorders of the silicate weathering proxy, Li isotopes. We analysed δ7 Li and [Li] in speleothems that formed during the past 200 ka in two well-studied Israeli caves (Soreq and Tzavoa), as well as in the overlying soils and rocks. Leaching and mass balance of these soils and rocks show that Li is dominantly sourced from weathering of the overlying aeolian silicate soils. Speleothem δ7 Li values are ubiquitously higher during glacials (∼23‰) than during interglacials (∼10‰), implying more congruent silicate weathering during interglacials (where ;congruent; means a high ratio of primary mineral dissolution to secondary mineral formation). These records provide information on the processes controlling weathering in Israel. Consideration of possible processes causing this change of weathering congruency indicates a primary role for temperature, with higher temperatures causing more congruent weathering (lower δ7Lispeleo). The strong relationship observed between speleothem δ7 Li and climate at these locations suggests that Li isotopes may be a powerful tool with which to understand the local controls on weathering at other sites, and could be used to assess the distribution of weathering changes accompanying climate change, such as that of Pleistocene glacial cycles.

  1. Control of Tobacco mosaic virus movement protein fate by CELL-DIVISION-CYCLE protein48.

    PubMed

    Niehl, Annette; Amari, Khalid; Gereige, Dalya; Brandner, Katrin; Mély, Yves; Heinlein, Manfred

    2012-12-01

    Like many other viruses, Tobacco mosaic virus replicates in association with the endoplasmic reticulum (ER) and exploits this membrane network for intercellular spread through plasmodesmata (PD), a process depending on virus-encoded movement protein (MP). The movement process involves interactions of MP with the ER and the cytoskeleton as well as its targeting to PD. Later in the infection cycle, the MP further accumulates and localizes to ER-associated inclusions, the viral factories, and along microtubules before it is finally degraded. Although these patterns of MP accumulation have been described in great detail, the underlying mechanisms that control MP fate and function during infection are not known. Here, we identify CELL-DIVISION-CYCLE protein48 (CDC48), a conserved chaperone controlling protein fate in yeast (Saccharomyces cerevisiae) and animal cells by extracting protein substrates from membranes or complexes, as a cellular factor regulating MP accumulation patterns in plant cells. We demonstrate that Arabidopsis (Arabidopsis thaliana) CDC48 is induced upon infection, interacts with MP in ER inclusions dependent on the MP N terminus, and promotes degradation of the protein. We further provide evidence that CDC48 extracts MP from ER inclusions to the cytosol, where it subsequently accumulates on and stabilizes microtubules. We show that virus movement is impaired upon overexpression of CDC48, suggesting that CDC48 further functions in controlling virus movement by removal of MP from the ER transport pathway and by promoting interference of MP with microtubule dynamics. CDC48 acts also in response to other proteins expressed in the ER, thus suggesting a general role of CDC48 in ER membrane maintenance upon ER stress.

  2. Endogenous and exogenous control of ecosystem function: N cycling in headwater streams

    SciTech Connect

    Mulholland, Patrick J; Valett, H. Maurice; Thomas, Steve; Webster, Jackson; Dahm, Cliff; Fellows, Christine; Crenshaw, Chelsea; Peterson, Chris G.

    2008-01-01

    Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of {sup 15}N as nitrate in six streams differing in riparian-stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in {sup 15}N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; {micro}g N {center_dot} m{sup -2} {center_dot} s{sup -1}) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (v{sub f}; mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.

  3. Designing responsive pattern generators: stable heteroclinic channel cycles for modeling and control.

    PubMed

    Horchler, Andrew D; Daltorio, Kathryn A; Chiel, Hillel J; Quinn, Roger D

    2015-02-25

    A striking feature of biological pattern generators is their ability to respond immediately to multisensory perturbations by modulating the dwell time at a particular phase of oscillation, which can vary force output, range of motion, or other characteristics of a physical system. Stable heteroclinic channels (SHCs) are a dynamical architecture that can provide such responsiveness to artificial devices such as robots. SHCs are composed of sequences of saddle equilibrium points, which yields exquisite sensitivity. The strength of the vector fields in the neighborhood of these equilibria determines the responsiveness to perturbations and how long trajectories dwell in the vicinity of a saddle. For SHC cycles, the addition of stochastic noise results in oscillation with a regular mean period. In this paper, we parameterize noise-driven Lotka-Volterra SHC cycles such that each saddle can be independently designed to have a desired mean sub-period. The first step in the design process is an analytic approximation, which results in mean sub-periods that are within 2% of the specified sub-period for a typical parameter set. Further, after measuring the resultant sub-periods over sufficient numbers of cycles, the magnitude of the noise can be adjusted to control the mean period with accuracy close to that of the integration step size. With these relationships, SHCs can be more easily employed in engineering and modeling applications. For applications that require smooth state transitions, this parameterization permits each state's distribution of periods to be independently specified. Moreover, for modeling context-dependent behaviors, continuously varying inputs in each state dimension can rapidly precipitate transitions to alter frequency and phase.

  4. Formation of 10-100 nm size-controlled emulsions through a sub-PIT cycle.

    PubMed

    Roger, Kevin; Cabane, Bernard; Olsson, Ulf

    2010-03-16

    We have re-examined the phase inversion temperature (PIT) emulsification process. This is a low-energy method that uses a physicochemical drive to produce very fine oil/water emulsions in the absence of high shear flows. We used the polyoxyethylene 8 cetyl ether (C(16)E(8))/hexadecane/water system, which has a PIT of 76.2 degrees C. We find that successful emulsification depends on two conditions. First, the mixture must be stirred at low speed throughout the whole process: this makes it possible to produce emulsions at surfactant concentrations that are too low to form an equilibrium microemulsion. Second, the stirred mixtures must be heated above a threshold called the clearing boundary (CB) and then quenched to lower temperatures. The clearing boundary is determined experimentally by a minimum in the turbidity of the stirred mixture, which results from solubilization of all the oil into swollen micelles. This matches the emulsification failure boundary, and it is expressed mathematically by the condition R*C(0) = 1, where R* is the radius that results from the oil/surfactant composition for monodisperse spheres and C(0) is the spontaneous spherical curvature of the surfactant. Thus, we show that such cycles do not need to cross the PIT. In fact, sub-PIT cycles and cross-PIT cycles give exactly the same result. These conditions lead to emulsions that have a narrow size distribution and a mean diameter controlled by the oil/surfactant ratio. The typical range of those diameters is 20-100 nm. Moreover, these emulsions have an excellent metastability, in contrast with emulsions made with shorter oil and surfactant molecules.

  5. Effects of Excess Succinate and Retrograde Control of Metabolite Accumulation in Yeast Tricarboxylic Cycle Mutants*

    PubMed Central

    Lin, An-Ping; Anderson, Sondra L.; Minard, Karyl I.; McAlister-Henn, Lee

    2011-01-01

    Cellular and mitochondrial metabolite levels were measured in yeast TCA cycle mutants (sdh2Δ or fum1Δ) lacking succinate dehydrogenase or fumarase activities. Cellular levels of succinate relative to parental strain levels were found to be elevated ∼8-fold in the sdh2Δ mutant and ∼4-fold in the fum1Δ mutant, and there was a preferential increase in mitochondrial levels in these mutant strains. The sdh2Δ and fum1Δ strains also exhibited 3–4-fold increases in expression of Cit2, the cytosolic form of citrate synthase that functions in the glyoxylate pathway. Co-disruption of the SFC1 gene encoding the mitochondrial succinate/fumarate transporter resulted in higher relative mitochondrial levels of succinate and in substantial reductions of Cit2 expression in sdh2Δsfc1Δ and fum1Δsfc1Δ strains as compared with sdh2Δ and fum1Δ strains, suggesting that aberrant transport of succinate out of mitochondria mediated by Sfc1 is related to the increased expression of Cit2 in sdh2Δ and fum1Δ strains. A defect (rtg1Δ) in the yeast retrograde response pathway, which controls expression of several mitochondrial proteins and Cit2, eliminated expression of Cit2 and reduced expression of NAD-specific isocitrate dehydrogenase (Idh) and aconitase (Aco1) in parental, sdh2Δ, and fum1Δ strains. Concomitantly, co-disruption of the RTG1 gene reduced the cellular levels of succinate in the sdh2Δ and fum1Δ strains, of fumarate in the fum1Δ strain, and citrate in an idhΔ strain. Thus, the retrograde response is necessary for maintenance of normal flux through the TCA and glyoxylate cycles in the parental strain and for metabolite accumulation in TCA cycle mutants. PMID:21841001

  6. Antecedent acute cycling exercise affects attention control: an ERP study using attention network test.

    PubMed

    Chang, Yu-Kai; Pesce, Caterina; Chiang, Yi-Te; Kuo, Cheng-Yuh; Fong, Dong-Yang

    2015-01-01

    The purpose of this study was to investigate the after-effects of an acute bout of moderate intensity aerobic cycling exercise on neuroelectric and behavioral indices of efficiency of three attentional networks: alerting, orienting, and executive (conflict) control. Thirty young, highly fit amateur basketball players performed a multifunctional attentional reaction time task, the attention network test (ANT), with a two-group randomized experimental design after an acute bout of moderate intensity spinning wheel exercise or without antecedent exercise. The ANT combined warning signals prior to targets, spatial cueing of potential target locations and target stimuli surrounded by congruent or incongruent flankers, which were provided to assess three attentional networks. Event-related brain potentials and task performance were measured during the ANT. Exercise resulted in a larger P3 amplitude in the alerting and executive control subtasks across frontal, central and parietal midline sites that was paralleled by an enhanced reaction speed only on trials with incongruent flankers of the executive control network. The P3 latency and response accuracy were not affected by exercise. These findings suggest that after spinning, more resources are allocated to task-relevant stimuli in tasks that rely on the alerting and executive control networks. However, the improvement in performance was observed in only the executively challenging conflict condition, suggesting that whether the brain resources that are rendered available immediately after acute exercise translate into better attention performance depends on the cognitive task complexity.

  7. Southern Ocean coccolithophore biogeography - controlling factors and implications for global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Nissen, Cara; Vogt, Meike; Münnich, Matthias; Gruber, Nicolas

    2017-04-01

    Southern Ocean phytoplankton biogeography is important for the biogeochemical cycling of carbon, silicate, and the transport of macronutrients to lower latitudes. With the discovery of the "Great Calcite Belt" (GBC), revealing an unexpectedly high prevalence of calcifying phytoplankton in the subtropical frontal region between 40-55°S, the relative importance of Southern Ocean coccolithophores for phytoplankton biomass, net primary productivity and the carbon cycle need to be revisited. Using a regional high-resolution model with an embedded ecosystem module (ROMS-BEC) for the Southern Ocean (24-78°S) that has been extended to include an explicit representation of coccolithophores, we assess the environmental drivers of Southern Ocean coccolithophore biogeography over the course of the growing season. We thereby focus on biotic interactions and the relative importance of top-down (grazing) versus bottom-up factors (light, nutrient, temperature) controlling growth and abundance. In our simulation, coccolithophores are an important member of the Southern Ocean phytoplankton community, contributing 13% to annually integrated net primary productivity south of 30°S. We estimate the integrated annual calcification rate to account for 40% of the satellite derived global estimate. Modeled coccolithophore biomass is highest in February and March in a latitudinal band between 40-55°S, when diatoms become heavily silicate limited. This region is characterized by a number of divergent fronts with a low Si:Fe ratio of waters supplied to the mixed layer, supporting an increased growth of coccolithophores at the expense of diatoms. We find top down controls to be the major control on the relative abundance of diatoms and coccolithophores in the Southern Ocean. We perform iron and silicate fertilization experiments to assess the effects of changed nutrient availability on coccolithophore abundance in the GCB. We find that changes in nutrient stoichiometry significantly alter

  8. Hydrologic control of carbon cycling and aged carbon discharge in the Congo River basin

    NASA Astrophysics Data System (ADS)

    Schefuß, Enno; Eglinton, Timothy I.; Spencer-Jones, Charlotte L.; Rullkötter, Jürgen; de Pol-Holz, Ricardo; Talbot, Helen M.; Grootes, Pieter M.; Schneider, Ralph R.

    2016-09-01

    The age of organic material discharged by rivers provides information about its sources and carbon cycling processes within watersheds. Although elevated ages in fluvially transported organic matter are usually explained by erosion of soils and sedimentary deposits, it is commonly assumed that mainly young organic material is discharged from flat tropical watersheds due to their extensive plant cover and rapid carbon turnover. Here we present compound-specific radiocarbon data of terrigenous organic fractions from a sedimentary archive offshore the Congo River, in conjunction with molecular markers for methane-producing land cover reflecting wetland extent. We find that the Congo River has been discharging aged organic matter for several thousand years, with apparently increasing ages from the mid- to the Late Holocene. This suggests that aged organic matter in modern samples is concealed by radiocarbon from atmospheric nuclear weapons testing. By comparison to indicators for past rainfall changes we detect a systematic control of organic matter sequestration and release by continental hydrology, mediating temporary carbon storage in wetlands. As aridification also leads to exposure and rapid remineralization of large amounts of previously stored labile organic matter, we infer that this process may cause a profound direct climate feedback that is at present underestimated in carbon cycle assessments.

  9. Controlling the duty cycle of holographic crossed gratings by in situ endpoint detection during development.

    PubMed

    Wang, Shiwei; Zeng, Lijiang

    2016-04-01

    A method of in situ development endpoint detection is proposed to control the duty cycle of holographic crossed gratings. Based on the observation that after the developer first touches the substrate surface the topography of the crossed grating undergoes an evolution process from a hole array of increasing diameter to a pillar array of decreasing diameter, we set up a development model. In this model, the shapes of both holes and pillars are assumed to have square in-plane cross sections, rotated 45° with respect to the main periodic directions, and straight side walls perpendicular to the grating plane. Thus, the main development process, including the transition from a hole array to a pillar array, can be characterized by a single parameter continuously, and the change of diffraction efficiency during the process can be theoretically calculated. Two different in situ development monitoring conditions were simulated and tested experimentally. Using this method, crossed gratings with various duty cycles were fabricated under different incident and monitoring conditions.

  10. Seasonal patterns of photosynthetic capacity: photoperiodic control and its carbon cycling implications

    NASA Astrophysics Data System (ADS)

    Bauerle, W.; Oren, R.; Way, D.; Qian, S.; Stoy, P. C.; Thornton, P. E.; Bowden, J.; Hoffman, F. M.; Reynolds, R.

    2012-12-01

    While temperature is an important driver of seasonal changes in photosynthetic physiology, photoperiod also regulates leaf activity. Climate change will extend growing seasons if temperature cues predominate, but photoperiod-controlled species will show limited responsiveness to warming. We show that photoperiod explains more seasonal variation in photosynthetic activity across 23 tree species than temperature. Although leaves remain green, photosynthetic capacity peaks just after summer solstice and declines with decreasing photoperiod, before air temperatures peak. In support of these findings, saplings grown at constant temperature, but exposed to an extended photoperiod maintained high photosynthetic capacity, while photosynthetic activity declined in saplings experiencing a naturally shortening photoperiod; leaves remained equally green in both treatments. Incorporating a photoperiodic correction of photosynthetic physiology into a global-scale terrestrial carbon cycle model significantly improves predictions of seasonal atmospheric CO2 cycling, demonstrating the benefit of such a function in coupled climate system models. Accounting for photoperiod-induced seasonality in photosynthetic parameters reduces modeled global gross primary production ~4 PgC y-1, resulting in a ~2 PgC y-1 decrease of net primary production. Such a correction is also needed in models estimating current carbon uptake based on remotely-sensed greenness. Photoperiod-associated declines in photosynthetic capacity could limit autumn carbon gain in forests, even if warming delays leaf senescence. Assessments of late season carbon sequestration under a changing climate should focus on potential adverse impacts of warming via increased ecosystem respiration.

  11. Load and Pi control flux through the branched kinetic cycle of myosin V.

    PubMed

    Kad, Neil M; Trybus, Kathleen M; Warshaw, David M

    2008-06-20

    Myosin V is a processive actin-based motor protein that takes multiple 36-nm steps to deliver intracellular cargo to its destination. In the laser trap, applied load slows myosin V heavy meromyosin stepping and increases the probability of backsteps. In the presence of 40 mm phosphate (P(i)), both forward and backward steps become less load-dependent. From these data, we infer that P(i) release commits myosin V to undergo a highly load-dependent transition from a state in which ADP is bound to both heads and its lead head trapped in a pre-powerstroke conformation. Increasing the residence time in this state by applying load increases the probability of backstepping or detachment. The kinetics of detachment indicate that myosin V can detach from actin at two distinct points in the cycle, one of which is turned off by the presence of P(i). We propose a branched kinetic model to explain these data. Our model includes P(i) release prior to the most load-dependent step in the cycle, implying that P(i) release and load both act as checkpoints that control the flux through two parallel pathways.

  12. Sand dune patterns on Titan controlled by long-term climate cycles

    NASA Astrophysics Data System (ADS)

    Ewing, Ryan C.; Hayes, Alex G.; Lucas, Antoine

    2015-01-01

    Linear sand dunes cover the equatorial latitudes of Saturn's moon Titan and are shaped by global wind patterns. These dunes are thought to reflect present-day diurnal, tidal and seasonal winds, but climate models have failed to reproduce observed dune morphologies with these wind patterns. Dunes diagnostic of a specific wind or formative timescale have remained elusive. Here we analyse radar imagery from NASA's Cassini spacecraft and identify barchan, star and reoriented dunes in sediment-limited regions of Titan's equatorial dune fields that diverge by 23° on average from the orientation of linear dunes. These morphologies imply shifts in wind direction and sediment availability. Using a numerical model, we estimate that the observed reorientation of dune crests to a change in wind direction would have taken around 3,000 Saturn years (1 Saturn year ~ 29.4 Earth years) or longer--a timescale that exceeds diurnal, seasonal or tidal cycles. We propose that shifts in winds and sediment availability are the product of long-term climate cycles associated with variations in Saturn's orbit. Orbitally controlled landscape evolution--also proposed to explain the distribution of Titan's polar lakes--implies a dune-forming climate on equatorial Titan that is analogous to Earth.

  13. Hypothalamic neural systems controlling the female reproductive life cycle: Gonadotropin-releasing hormone, glutamate, and GABA

    PubMed Central

    Maffucci, Jacqueline A.; Gore, Andrea C.

    2009-01-01

    The hypothalamic-pituitary-gonadal (HPG) axis undergoes a number of changes throughout the reproductive life cycle that are responsible for the development, puberty, adulthood, and senescence of reproductive systems. This natural progression is dictated by the neural network controlling the hypothalamus including the cells that synthesize and release gonadotropin-releasing hormone (GnRH) and their regulatory neurotransmitters. Glutamate and GABA are the primary excitatory and inhibitory neurotransmitters in the central nervous system, and as such contribute a great deal to modulating this axis throughout the lifetime via their actions on receptors in the hypothalamus, both directly on GnRH neurons as well as indirectly though other hypothalamic neural networks. Interactions among GnRH neurons, glutamate, and GABA, including the regulation of GnRH gene and protein expression, hormone release, and modulation by estrogen, are critical to age-appropriate changes in reproductive function. Here, we present evidence for the modulation of GnRH neurosecretory cells by the balance of glutamate and GABA in the hypothalamus, and the functional consequences of these interactions on reproductive physiology across the life cycle. PMID:19349036

  14. Deep crustal fracture zones control fluid escape and the seismic cycle in the Cascadia subduction zone

    NASA Astrophysics Data System (ADS)

    Tauzin, Benoît; Reynard, Bruno; Perrillat, Jean-Philippe; Debayle, Eric; Bodin, Thomas

    2017-02-01

    Seismic activity and non-volcanic tremors are often associated with fluid circulation resulting from the dehydration of subducting plates. Tremors in the overriding continental crust of several subduction zones suggest fluid circulation at shallower depths, but potential fluid pathways are still poorly documented. Using receiver function analysis in the Cascadia subduction zone, we provide evidence for a seismic discontinuity near 15 km depth in the crust of the overriding North American plate. This interface is segmented, and its interruptions are spatially correlated with conductive regions of the forearc and shallow swarms of seismicity and non-volcanic tremors. These observations suggest that fluid circulation in the overriding plate is controlled by fault zones separating blocks of accreted terranes. These zones constitute fluid escape routes that may influence the seismic cycle by releasing fluid pressure from the megathrust.

  15. High-precision atom localization via controllable spontaneous emission in a cycle-configuration atomic system.

    PubMed

    Ding, Chunling; Li, Jiahua; Yu, Rong; Hao, Xiangying; Wu, Ying

    2012-03-26

    A scheme for realizing two-dimensional (2D) atom localization is proposed based on controllable spontaneous emission in a coherently driven cycle-configuration atomic system. As the spatial-position-dependent atom-field interaction, the frequency of the spontaneously emitted photon carries the information about the position of the atom. Therefore, by detecting the emitted photon one could obtain the position information available, and then we demonstrate high-precision and high-resolution 2D atom localization induced by the quantum interference between the multiple spontaneous decay channels. Moreover, we can achieve 100% probability of finding the atom at an expected position by choosing appropriate system parameters under certain conditions.

  16. The feedback control cycle as regulator of past and future mineral supply

    NASA Astrophysics Data System (ADS)

    Wellmer, Friedrich-W.; Dalheimer, Manfred

    2012-10-01

    Mineral supply is controlled by a feedback mechanism. When there is a shortage of a commodity in a market economy, prices will rise, triggering this mechanism. The expectation of high financial returns will encourage inventiveness and creativity in the quest for new solutions. On the supply side, for primary resources, the appropriate response is to cut losses in the mining process, to lower the cut-off grade, to improve recoveries in the beneficiation and smelting processes, to expand existing production facilities, and to discover and bring into production new deposits. For secondary resources, the key to increasing the supply lies in improving recycling rates by better technology, reprocessing lower-grade scrap which becomes economic because of increased prices, and reducing downgrading to optimize the usefulness of secondary materials. On the demand side, implementation of new and more efficient processes, development of substitution technologies, material savings, and the invention of entirely new technologies that fulfill the same function without the need of using the scarce and suddenly more expensive material are effective reactions to a price rise. The effectiveness of this self-regulating mechanism can be shown by examples of historical price peaks of metals, such as Mo, Co, and Ta, and the current rare earth elements peak. Concerning supply from secondary resources, a model is developed in order to determine how far the supply from this resource domain can be achieved and how the recycling rate is influenced by growth rate and lifetime. The feedback control cycle of mineral supply is influenced on the demand side by ever shorter life cycles, by products getting more complex with ever more elements involved in their production, and by an increase in element dispersion. All these factors have an immediate effect on the feasibility of sourcing raw materials from the technosphere. The supply side of primary materials is influenced by increasing lead times

  17. Technological and life cycle assessment of organics processing odour control technologies.

    PubMed

    Bindra, Navin; Dubey, Brajesh; Dutta, Animesh

    2015-09-15

    As more municipalities and communities across developed world look towards implementing organic waste management programmes or upgrading existing ones, composting facilities are emerging as a popular choice. However, odour from these facilities continues to be one of the most important concerns in terms of cost & effective mitigation. This paper provides a technological and life cycle assessment of some of the different odour control technologies and treatment methods that can be implemented in organics processing facilities. The technological assessment compared biofilters, packed tower wet scrubbers, fine mist wet scrubbers, activated carbon adsorption, thermal oxidization, oxidization chemicals and masking agents. The technologies/treatment methods were evaluated and compared based on a variety of operational, usage and cost parameters. Based on the technological assessment it was found that, biofilters and packed bed wet scrubbers are the most applicable odour control technologies for use in organics processing faculties. A life cycle assessment was then done to compare the environmental impacts of the packed-bed wet scrubber system, organic (wood-chip media) bio-filter and inorganic (synthetic media) bio-filter systems. Twelve impact categories were assessed; cumulative energy demand (CED), climate change, human toxicity, photochemical oxidant formation, metal depletion, fossil depletion, terrestrial acidification, freshwater eutrophication, marine eutrophication, terrestrial eco-toxicity, freshwater eco-toxicity and marine eco-toxicity. The results showed that for all impact categories the synthetic media biofilter had the highest environmental impact, followed by the wood chip media bio-filter system. The packed-bed system had the lowest environmental impact for all categories.

  18. Human beta-defensin-2 controls cell cycle in malignant epithelial cells: in vitro study.

    PubMed

    Zhuravel, E; Shestakova, T; Efanova, O; Yusefovich, Yu; Lytvin, D; Soldatkina, M; Pogrebnoy, P

    2011-09-01

    In the present research we analyze the mechanism of human beta-defensin-2 (hBD-2) influence on cultured malignant epithelial cell growth. The analysis of a concentration-dependent effect of recombinant hBD-2 (rec-hBD-2) on cell growth patterns and cell cycle distribution has been performed in vitro with 2 cell lines (human lung adenocarcinoma A549 cells and human epidermoid carcinoma A431 cells) using MTT test, flow cytometry and direct cell counting. To study intracellular localization of hBD-2 immunocytofluorescent and immunocytochemical analyses were applied, and effect of hBD-2 on signal cascades involved in cell cycle regulation has been studied by Western blotting. According to our data, rec-hBD-2 exerts a concentration-dependent effect on the viability of cultured A549 and A431 cells. It causes proproliferative effect at concentrations below 1 nM, significant suppression of cell proliferation at concentration range from 10 nM to 1 μM (p<0.05), and cell death at higher concentrations. Using flow cytometry we have demonstrated that hBD-2 dependent growth suppression is realized via cell cycle arrest at G1/S phase (p<0.05). Also, we have registered significant activation of pRB and decreased expression of Cyclin D1 in cells treated with the defensin compared to untreated control cells, while the expression of p53 remains unaffected. The study of intracellular localization of hBD-2 in these cells has revealed that exogeneously added defensin molecules enter the cells, are distributed throughout the cytoplasm and could be detected in cell nuclei. The model study using A549 cells treated with 1,25-(OH)(2)D(3) has shown similar cell growth suppression effect of native endogenously produced hBD-2. The results of our study suggest that in malignant epithelial cells hBD-2 may control cell growth via arrest of G1/S transition and activation of pRB.

  19. Rapid Quench Cold-Seal Apparatus with Computer-Controlled Pressure and Temperature Cycling

    NASA Astrophysics Data System (ADS)

    Johnston, A.; Senkovich, D.

    2007-12-01

    We have constructed two computer-controlled, rapid quench, hydrothermal apparatuses that are ideal for experimentation on volcanological, geothermal, and ore deposit research problems. The devices can achieve maximum pressures of about 2 kbar and temperatures to 1100C, have the ability for experiments to be quenched very rapidly in a water-cooled environment, and are interfaced with computers which can control any regimen of pressure and/or temperature cycling that may be desired, accomplished via Lab-View software and data acquisition and motion control boards from National Instruments. The rapid quench aspects of the design were developed originally by Dr. Phil Ihinger and have subsequently been adopted by many labs around the world; a good summary description of these aspects of the equipment, and the use of filler-rods for controlling redox conditions in such equipment, are provided by Matthews et al. (2004, Am. Mineral., 88: 701-707). Our design has fixed Rene 41 pressure vessels, furnaces that are raised and lowered by computer controlled pneumatic cylinders and water cooling systems that are controlled by computer operated solenoid valves. The novel feature of our design is the pressure generation and control systems. We coupled the seal-ends of commercially available (HIP) pressure generators to shop-built linear actuators consisting of nearly frictionless ball lead screws within thick walled stainless steel housings. These in turn are driven by NEMA size 23 stepper motors coupled to 100:1 gear reduction units. The actuators require 21 revolutions to achieve their full stroke of 12.7 cm which displaces about 10 cc of fluid. Operating the motors at the relatively low resolution of 800 steps per revolution leads to about 132,000 steps per cm of travel of the pressure-generating piston, providing exceptionally high precision and excellent pressure control. Instantaneous decompression can be achieved by simply opening a valve while motor-controlled

  20. Hormonal, follicular and endometrial dynamics in letrozole-treated versus natural cycles in patients undergoing controlled ovarian stimulation.

    PubMed

    Bedaiwy, Mohamed A; Abdelaleem, Mahmoud A; Hussein, Mostafa; Mousa, Noha; Brunengraber, Lisa N; Casper, Robert F

    2011-06-21

    The objective of this study was to compare letrozole-stimulated cycles to natural cycles in 208 patients undergoing intrauterine insemination (IUI) between July of 2004 and January of 2007. Group I (n = 47) received cycle monitoring only (natural group), Group II (n = 125) received letrozole 2.5 mg/day on cycle days three to seven, and Group III (n = 36) received letrozole 5 mg/day on cycle days three to seven. There were no differences between the groups in endometrial thickness or P₄ on the day of hCG. Estradiol levels had higher variation in the second half of the follicular phase in both letrozole-treated groups compared to the control group. Estradiol per preovulatory follicle was similar in both letrozole cycles to that observed in the natural cycles. LH was lower on the day of hCG administration in the letrozole 2.5 mg/day group vs. the natural group. In summary, letrozole results in some minor changes in follicular, hormonal and endometrial dynamics compared to natural cycles. Increased folliculogenesis and pregnancy rates were observed in the letrozole-treated groups compared to the natural group. These findings need to be confirmed in larger, prospective studies.

  1. Length of Menstrual Cycle and Risk of Endometriosis: A Meta-Analysis of 11 Case-Control Studies.

    PubMed

    Wei, Ming; Cheng, Yanfei; Bu, Huaien; Zhao, Ye; Zhao, Wenli

    2016-03-01

    Endometriosis is a complex disease that affects a large number of women worldwide and may cause pain and infertility. To systematically review published studies evaluating the relationship between menstrual cycle length and risk of endometriosis. We searched the Cochrane Library, PubMed, Web of Science, and EMBASE in databases in July 2014 using the keywords "case-control studies," "epidemiologic determinants," "risk factors," "menstrual cycle," "menstrual length," "menstrual character," and "endometriosis." We included case-control studies published in English that investigated cases of surgically confirmed endometriosis and examined the relationship between endometriosis risk and menstrual cycle. Eleven articles that met the inclusion criteria included data of 3392 women with endometriosis and 5006 controls. Fixed-effects and random-effects models were used for the evaluation. For the association of risk of endometriosis and menstrual cycle length shorter than or equal to 27 days (SEQ27) or length longer than or equal to 29 days (LEQ29), the odds ratio was 1.22 (95% confidence interval [CI]: 1.05-1.43) and 0.68 (95% CI: 0.48-0.96), respectively. In conclusion, this meta-analysis suggests that menstrual cycle length SEQ27 increase the risk of endometriosis and cycle length LEQ29 decrease the risk.

  2. Controls on the diurnal streamflow cycles in two subbasins of an alpine headwater catchment

    NASA Astrophysics Data System (ADS)

    Mutzner, Raphael; Weijs, Steven V.; Tarolli, Paolo; Calaf, Marc; Oldroyd, Holly J.; Parlange, Marc B.

    2015-05-01

    In high-altitude alpine catchments, diurnal streamflow cycles are typically dominated by snowmelt or ice melt. Evapotranspiration-induced diurnal streamflow cycles are less observed in these catchments but might happen simultaneously. During a field campaign in the summer 2012 in an alpine catchment in the Swiss Alps (Val Ferret catchment, 20.4 km2, glaciarized area: 2%), we observed a transition in the early season from a snowmelt to an evapotranspiration-induced diurnal streamflow cycle in one of two monitored subbasins. The two different cycles were of comparable amplitudes and the transition happened within a time span of several days. In the second monitored subbasin, we observed an ice melt-dominated diurnal cycle during the entire season due to the presence of a small glacier. Comparisons between ice melt and evapotranspiration cycles showed that the two processes were happening at the same times of day but with a different sign and a different shape. The amplitude of the ice melt cycle decreased exponentially during the season and was larger than the amplitude of the evapotranspiration cycle which was relatively constant during the season. Our study suggests that an evapotranspiration-dominated diurnal streamflow cycle could damp the ice melt-dominated diurnal streamflow cycle. The two types of diurnal streamflow cycles were separated using a method based on the identification of the active riparian area and measurement of evapotranspiration.

  3. Ammonia control and neurocognitive outcome among urea cycle disorder patients treated with glycerol phenylbutyrate.

    PubMed

    Diaz, George A; Krivitzky, Lauren S; Mokhtarani, Masoud; Rhead, William; Bartley, James; Feigenbaum, Annette; Longo, Nicola; Berquist, William; Berry, Susan A; Gallagher, Renata; Lichter-Konecki, Uta; Bartholomew, Dennis; Harding, Cary O; Cederbaum, Stephen; McCandless, Shawn E; Smith, Wendy; Vockley, Gerald; Bart, Stephen A; Korson, Mark S; Kronn, David; Zori, Roberto; Merritt, J Lawrence; C S Nagamani, Sandesh; Mauney, Joseph; Lemons, Cynthia; Dickinson, Klara; Moors, Tristen L; Coakley, Dion F; Scharschmidt, Bruce F; Lee, Brendan

    2013-06-01

    Glycerol phenylbutyrate is under development for treatment of urea cycle disorders (UCDs), rare inherited metabolic disorders manifested by hyperammonemia and neurological impairment. We report the results of a pivotal Phase 3, randomized, double-blind, crossover trial comparing ammonia control, assessed as 24-hour area under the curve (NH3 -AUC0-24hr ), and pharmacokinetics during treatment with glycerol phenylbutyrate versus sodium phenylbutyrate (NaPBA) in adult UCD patients and the combined results of four studies involving short- and long-term glycerol phenylbutyrate treatment of UCD patients ages 6 and above. Glycerol phenylbutyrate was noninferior to NaPBA with respect to ammonia control in the pivotal study, with mean (standard deviation, SD) NH3 -AUC0-24hr of 866 (661) versus 977 (865) μmol·h/L for glycerol phenylbutyrate and NaPBA, respectively. Among 65 adult and pediatric patients completing three similarly designed short-term comparisons of glycerol phenylbutyrate versus NaPBA, NH3 -AUC0-24hr was directionally lower on glycerol phenylbutyrate in each study, similar among all subgroups, and significantly lower (P < 0.05) in the pooled analysis, as was plasma glutamine. The 24-hour ammonia profiles were consistent with the slow-release behavior of glycerol phenylbutyrate and better overnight ammonia control. During 12 months of open-label glycerol phenylbutyrate treatment, average ammonia was normal in adult and pediatric patients and executive function among pediatric patients, including behavioral regulation, goal setting, planning, and self-monitoring, was significantly improved. Glycerol phenylbutyrate exhibits favorable pharmacokinetics and ammonia control relative to NaPBA in UCD patients, and long-term glycerol phenylbutyrate treatment in pediatric UCD patients was associated with improved executive function (ClinicalTrials.gov NCT00551200, NCT00947544, NCT00992459, NCT00947297). (HEPATOLOGY 2012). Copyright © 2012 American Association for the

  4. Biophysical Controls on Carbon Cycling in Restored and Unrestored Urban Streams

    NASA Astrophysics Data System (ADS)

    Larsen, L. G.; Harvey, J. W.; Singh, J. D.; Sinclair, G. A.; Langston, T.; Maglio, M. M.

    2012-12-01

    Stream restoration is a multibillion dollar industry, yet how restoration impacts the ecological functioning of streams remains poorly understood. Because stream restoration may alter numerous biophysical controls, including light availability (through tree removal during bank regrading), hydraulics, sediment characteristics, and/or nutrient concentrations, it can be challenging to achieve a general understanding of how different aspects of stream restoration design influence ecosystem function (e.g., carbon cycling). In this study we combined strategies of continuously monitoring hydrology, turbidity, and dissolved oxygen at a station with spatially distributed but temporally sparse synoptic sampling to understand how restoration and land-use impact carbon fixation and respiration in urban streams. The study was performed over three years in three adjacent 3rd-4th order stream reaches in the urban Chesapeake Bay watershed, one of which was restored in 2002 using the ubiquitous Natural Channel Design method. By parsing the dissolved oxygen time series into contributions from respiration and gross primary production, we found the unrestored urban reach to be the most heterotrophic. It removed two times more carbon from the stream to the atmosphere than an unrestored suburban stream that was nutrient impacted and five times more carbon than the restored urban stream. The synoptic sampling revealed that nutrients, light, and hydrodynamic disturbance were the primary controls on carbon fixation and respiration, with fine sediment also exhibiting importance, likely as a vehicle for nutrient transport. Low rates of net carbon removal in the restored stream arose from high light availability resulting in high primary production, combined with low fine sediment availability restricting respiration. Thus, while restoration may have been effective for stream stabilization, it has decreased the functionality of the stream for net carbon removal to the atmosphere. Surprisingly

  5. The silica dynamics of deforestation: new evidence for a biologically controlled Si cycle

    NASA Astrophysics Data System (ADS)

    Struyf, Eric; Smis, Adriaan; Clymans, Wim; Govers, Gerard; van Wesemael, Bas; Frot, Elisabeth; Batelaan, Okke; Goos, Peter; van Damme, Stefan; Meire, Patrick

    2010-05-01

    Amorphous, biogenic Si (ASi) is stored in large amounts in terrestrial ecosystems. The study of this terrestrial ASi pool and its influence on watershed scale silica fluxes, remains in an absolute pioneer research stage. These Si budget studies have not included the biogenic amorphous Si stock and related fluxes. This hampers our ability to accurately quantify terrestrial cycling of Si, which is -through ocean carbon burial and CO2 uptake during terrestrial Si weathering- intricately linked to global carbon budgets. We have studied detailed year-round concentration and flux patterns of dissolved (DSi) and amorphous Si in 60 small watersheds in the Scheldt river basin. Results show that transport of Si through the catchments is controlled by a complex set of terrestrial and aquatic processes, with land use and prominence of ecosystem types an important controlling factor. Based on high frequency discharge measurements and concurrent analysis of ASi and DSi concentrations during intense precipitation events, we were able to attribute a percentage of yearly ASi and DSi fluxes to both base flow and precipitation event related surface run-off. Our results show ASi and DSi concentrations in upstream river basins are intricately linked to each other and to discharge, and ASi transport constitutes an important part of the total transport of Si. The ASi mainly originates from agricultural cropland soils. We have also developed a new concept accounting for changes in silica fluxes after deforestation on different time-scales. Our concept is supported by previously collected datasets, and our new comprehensive dataset in the Scheldt River basin. The combined results indicate that immediately after deforestation, silica fluxes increase as a result of a recycling pulse of DSi from forest soil ASi, as well as increased ASi efflux. When the soil ASi pool is depleted, a new equilibrium is reached, where DSi fluxes are low compared to the pristine forest equilibrium phase. The

  6. The chemopreventive activity of apple against carcinogenesis: antioxidant activity and cell cycle control.

    PubMed

    Ribeiro, Flávia A P; Gomes de Moura, Carolina F; Aguiar, Odair; de Oliveira, Flavia; Spadari, Regina C; Oliveira, Nara R C; Oshima, Celina T F; Ribeiro, Daniel A

    2014-09-01

    Apples and their derivatives are rich in phytochemicals, including flavonoids (catechins, flavonols, quercetin) and phenolic acids (quercetin glycosides, catechin, epicatechin, procyanidins), vitamins, and fibers, that confer an important antioxidant property. Chemoprevention is defined by the use of natural or synthetic agents to interfere with the progression, reverse, or inhibit carcinogenesis, thereby reducing the risk of developing clinically invasive disease. The aim of this article is to present data generated from the use of apples as a chemopreventive agent in carcinogenesis using in-vivo and in-vitro test systems. Apple and its bioactive compounds can exert chemopreventive properties as a result of antioxidant activity and cell cycle control. However, future focus of research on apple such as identifying the specific phytochemical responsible for the anticarcinogenic effect, timing of consumption, and adequate amount of apples to achieve the best preventive effect using human large randomized-controlled trials is needed. Furthermore, animal studies are also relevant for better understanding the role of this fruit in human health as well as modulation of degenerative diseases such as cancer. Therefore, this area warrants further investigation as a new way of thinking, which would apply not only to apples but also to other fruit used as promising therapeutic agents against human diseases.

  7. Immunological control of cell cycle aberrations for the avoidance of oncogenesis: the case of tetraploidy.

    PubMed

    Senovilla, Laura; Galluzzi, Lorenzo; Castedo, Maria; Kroemer, Guido

    2013-05-01

    Tetraploid cells--cells that contain twice the normal amount of DNA--are more prone to neoplastic transformation than their normal, diploid counterparts since they are genomically unstable and frequently undergo asymmetric, multipolar cell divisions. Similar to many other genomic aberrations, tetraploidization is normally avoided by multiple, nonredundant cell-intrinsic mechanisms that are tied to cell cycle checkpoints. Unexpectedly, tetraploidization is also under the control of a cell-extrinsic mechanism determined by the immune system. Indeed, oncogene- or carcinogen-induced cancers developing in immunodeficient mice contain cells with a higher DNA content than similar tumors growing in immunocompetent hosts. Moreover, cancer cell lines that have been rendered tetraploid in vitro grow normally in immunodeficient mice, yet almost fail to generate tumors in immunocompetent animals. One of the mechanisms whereby the immune system recognizes tetraploid cells originates from tetraploidy causing an endoplasmic reticulum (ER) stress response that culminates in the exposure of the ER protein calreticulin on the cell surface. Hence, tetraploidy exemplifies a potentially oncogenic alteration that is repressed by a combination of cell-autonomous mechanisms and immunosurveillance. Oncogenesis and tumor progression require the simultaneous failure of both such control systems.

  8. Spatial variability in mercury cycling and relevant biogeochemical controls in the Florida Everglades.

    PubMed

    Liu, Guangliang; Cai, Yong; Mao, Yuxiang; Scheidt, Daniel; Kalla, Peter; Richards, Jennifer; Scinto, Leonard J; Tachiev, Georgio; Roelant, David; Appleby, Charlie

    2009-06-15

    Spatial patterns in mercury cycling and bioaccumulation at the landscape level in the Everglades were investigated by collecting and analyzing multimedia samples for mercury species and biogeochemical characteristics from 228 randomly located stations. Higher total mercury (THg) in environmental compartments (surface water, soil, flocculent detrital material (floc), and periphyton) generally occurred in the northern and central Everglades, but higher THg in water and periphyton in the Everglades National Park was an exception. Multiple biogeochemical characteristics, such as surface water dissolved organic matter (DOC(sw)), pH, chloride, and compositional properties of solid compartments (soil and floc), were identified to be important factors controlling THg distribution. Methylmercury (MeHg) was also higher in the northern Everglades for water, soil, and floc, but not for periphyton. Higher mosquitofish THg and bioaccumulation factor were observed in the central and southern Everglades, partially in accordance with periphyton MeHg distribution, but not in the "hot spot" areas of water, soil, or floc MeHg. The discrepancy in mercury bioaccumulation and mercury distribution in environmental compartments suggests that in addition to MeHg production, biogeochemical controls that make MeHg available to aquatic organisms, such as DOC(sw) and compositional properties of soil and floc, are important in mercury bioaccumulation.

  9. The potential for control of carbon dioxide emissions from integrated gasification/combined-cycle systems

    SciTech Connect

    Livengood, C.D.; Doctor, R.D.; Molburg, J.C.; Thimmapuram, P.; Berry, G.F.

    1994-06-01

    Initiatives to limit carbon dioxide (CO{sub 2}) emissions have drawn considerable interest to integrated gasification/combined-cycle (IGCC) power generation, a process that reduces CO{sub 2} production through efficient fuel used is amenable to CO{sub 2} capture. This paper presents a comparison of energy systems that encompass fuel supply, an IGCC system, CO{sub 2} recovery using commercial technologies, CO{sub 2} transport by pipeline, and land-based sequestering in geological reservoirs. The intent is to evaluate the energy-efficiency impacts of controlling CO{sub 2} in such systems and to provide the CO{sub 2} budget, or an to equivalent CO{sub 2}`` budget, associated with each of the individual energy-cycle steps. The value used for the ``equivalent CO{sub 2}`` budget is 1 kg/kWh CO{sub 2}. The base case for the comparison is a 457-MW IGCC system that uses an air-blown Kellogg-Rust-Westinghouse (KRW) agglomerating fluidized-bed gasifier, Illinois No. 6 bituminous coal, and in-bed sulfur removal. Mining, preparation, and transportation of the coal and limestone result in a net system electric power production of 454 MW with a 0.835 kg/kwh CO{sub 2} release rate. For comparison, the gasifier output is taken through a water-gas shift to convert CO to CO{sub 2} and then processed in a glycol-based absorber unit to recover CO{sub 2} Prior to the combustion turbine. A 500-km pipeline then transports the CO{sub 2} for geological sequestering. The net electric power production for the system with CO{sub 2} recovery is 381 MW with a 0.156 kg/kwh CO{sub 2} release rate.

  10. Pericyte contractility controls endothelial cell cycle progression and sprouting: insights into angiogenic switch mechanics.

    PubMed

    Durham, Jennifer T; Surks, Howard K; Dulmovits, Brian M; Herman, Ira M

    2014-11-01

    Microvascular stability and regulation of capillary tonus are regulated by pericytes and their interactions with endothelial cells (EC). While the RhoA/Rho kinase (ROCK) pathway has been implicated in modulation of pericyte contractility, in part via regulation of the myosin light chain phosphatase (MLCP), the mechanisms linking Rho GTPase activity with actomyosin-based contraction and the cytoskeleton are equivocal. Recently, the myosin phosphatase-RhoA-interacting protein (MRIP) was shown to mediate the RhoA/ROCK-directed MLCP inactivation in vascular smooth muscle. Here we report that MRIP directly interacts with the β-actin-specific capping protein βcap73. Furthermore, manipulation of MRIP expression influences pericyte contractility, with MRIP silencing inducing cytoskeletal remodeling and cellular hypertrophy. MRIP knockdown induces a repositioning of βcap73 from the leading edge to stress fibers; thus MRIP-silenced pericytes increase F-actin-driven cell spreading twofold. These hypertrophied and cytoskeleton-enriched pericytes demonstrate a 2.2-fold increase in contractility upon MRIP knockdown when cells are plated on a deformable substrate. In turn, silencing pericyte MRIP significantly affects EC cycle progression and angiogenic activation. When MRIP-silenced pericytes are cocultured with capillary EC, there is a 2.0-fold increase in EC cycle entry. Furthermore, in three-dimensional models of injury and repair, silencing pericyte MRIP results in a 1.6-fold elevation of total tube area due to EC network formation and increased angiogenic sprouting. The pivotal role of MRIP expression in governing pericyte contractile phenotype and endothelial growth should lend important new insights into how chemomechanical signaling pathways control the "angiogenic switch" and pathological angiogenic induction. Copyright © 2014 the American Physiological Society.

  11. Protein farnesyltransferase in plants: molecular characterization and involvement in cell cycle control.

    PubMed Central

    Qian, D; Zhou, D; Ju, R; Cramer, C L; Yang, Z

    1996-01-01

    Farnesylation is required for membrane targeting, protein-protein interactions, and the biological activity of key regulatory proteins, such as Ras small GTPases and protein kinases in a wide range of eukaryotes. In this report, we describe the molecular identification of a plant protein farnesyltransferase (FTase) and evidence for its role in the control of the cell cycle in plants. A pea gene encoding a homolog of the FTase beta subunit was previously cloned using a polymerase chain reaction-based strategy. A similar approach was used to clone a pea gene encoding a homolog of the FTase alpha subunit. The biochemical function of the pea FTase homologs was demonstrated by the reconstitution of FTase enzyme activity using FTase fusion proteins coexpressed in Escherichia coll. RNA gel blot analyses showed that levels of FTase mRNAs are generally higher in tissues, such as those of nodules, that are active in cell division. The relationship of FTase to cell division was further analyzed during the growth of suspension-cultured tobacco BY-2 cells. A biphasic fluctuation of FTase enzyme activity preceded corresponding changes in mitotic activity at the early log phase of cell growth. Moreover, manumycin, a specific inhibitor of FTase, was effective in inhibiting mitosis and growth in these cells. Using synchronized BY-2 cells, manumycin completely blocked mitosis when added at the early S phase but not when added at the G2 phase. These data suggest that FTase is required for the plant cell cycle, perhaps by modulating the progression through the S phase and the transition from G1 to the S phase. PMID:8989889

  12. Nutrient control of microbial carbon cycling along an ombrotrophic-minerotrophic peatland gradient

    NASA Astrophysics Data System (ADS)

    Keller, Jason K.; Bauers, Angela K.; Bridgham, Scott D.; Kellogg, Laurie E.; Iversen, Colleen M.

    2006-09-01

    Future climate change and other anthropogenic activities are likely to increase nutrient availability in many peatlands, and it is important to understand how these additional nutrients will influence peatland carbon cycling. We investigated the effects of nitrogen and phosphorus on aerobic CH4 oxidation, anaerobic carbon mineralization (as CO2 and CH4 production), and anaerobic nutrient mineralization in a bog, an intermediate fen, and a rich fen in the Upper Peninsula of Michigan. We utilized a 5-week laboratory nutrient amendment experiment in conjunction with a 6-year field nutrient fertilization experiment to consider how the relative response to nitrogen and phosphorus differed among these wetlands over the short and long term. Field fertilizations generally increased nutrient availability in the upper 15 cm of peat and resulted in shifts in the vegetation community in each peatland. High nitrogen concentrations inhibited CH4 oxidation in bog peat during short-term incubations; however, long-term fertilization with lower concentrations of nitrogen stimulated rates of CH4 oxidation in bog peat. In contrast, no nitrogen effects on CH4 oxidation were observed in the intermediate or rich fen peat. Anaerobic carbon mineralization in bog peat was consistently inhibited by increased phosphorus availability, but similar phosphorus additions had few effects in the intermediate fen and stimulated CH4 production and nutrient mineralization in the rich fen. Our results demonstrate that nitrogen and phosphorus are important controls of peatland microbial carbon cycling; however, the role of these nutrients can differ over the short and long term and is strongly mediated by peatland type.

  13. Cell Cycle Control and DNA Damage Response of Conditionally Immortalized Urothelial Cells

    PubMed Central

    Dixon, Bradley P.; Henry, Jeff; Siroky, Brian J.; Chu, Albert; Groen, Pamela A.; Bissler, John J.

    2011-01-01

    Background Children with complex urogenital anomalies often require bladder reconstruction. Gastrointestinal tissues used in bladder augmentations exhibit a greatly increased risk of malignancy, and the bladder microenvironment may play a role in this carcinogenesis. Investigating the influences of the bladder microenvironment on gastrointestinal and urothelial cell cycle checkpoint activation and DNA damage response has been limited by the lack of an appropriate well-differentiated urothelial cell line system. Methodology/Principal Findings To meet this need, we have developed a well-differentiated conditionally immortalized urothelial cell line by isolating it from the H-2Kb-tsA58 transgenic mouse. These cells express a thermosensitive SV40 large T antigen that can be deactivated by adjustment of cell culture conditions, allowing the cell line to regain normal control of the cell cycle. The isolated urothelial cell line demonstrates a polygonal, dome-shaped morphology, expresses cytokeratin 18, and exhibits well-developed tight junctions. Adaptation of the urothelial cell line to hyperosmolal culture conditions induces expression of both cytokeratin 20 and uroplakin II, markers of a superficial urothelial cell or “umbrella cell.” This cell line can be maintained indefinitely in culture under permissive conditions but when cultured under non-permissive conditions, large T antigen expression is reduced substantially, leading to increased p53 activity and reduced cellular proliferation. Conclusions/Significance This new model of urothelial cells, along with gastrointestinal cell lines previously derived from the H-2Kb-tsA58 transgenic mouse, will be useful for studying the potential mechanisms of carcinogenesis of the augmented bladder. PMID:21305048

  14. Stochastic model for tumor control probability: effects of cell cycle and (a)symmetric proliferation.

    PubMed

    Dhawan, Andrew; Kaveh, Kamran; Kohandel, Mohammad; Sivaloganathan, Sivabal

    2014-11-22

    Estimating the required dose in radiotherapy is of crucial importance since the administrated dose should be sufficient to eradicate the tumor and at the same time should inflict minimal damage on normal cells. The probability that a given dose and schedule of ionizing radiation eradicates all the tumor cells in a given tissue is called the tumor control probability (TCP), and is often used to compare various treatment strategies used in radiation therapy. In this paper, we aim to investigate the effects of including cell-cycle phase on the TCP by analyzing a stochastic model of a tumor comprised of actively dividing cells and quiescent cells with different radiation sensitivities. Moreover, we use a novel numerical approach based on the method of characteristics for partial differential equations, validated by the Gillespie algorithm, to compute the TCP as a function of time. We derive an exact phase-diagram for the steady-state TCP of the model and show that at high, clinically-relevant doses of radiation, the distinction between active and quiescent tumor cells (i.e. accounting for cell-cycle effects) becomes of negligible importance in terms of its effect on the TCP curve. However, for very low doses of radiation, these proportions become significant determinants of the TCP. We also present the results of TCP as a function of time for different values of asymmetric division factor. We observe that our results differ from the results in the literature using similar existing models, even though similar parameters values are used, and the reasons for this are discussed.

  15. Lyapunov-based control of limit cycle oscillations in uncertain aircraft systems

    NASA Astrophysics Data System (ADS)

    Bialy, Brendan

    Store-induced limit cycle oscillations (LCO) affect several fighter aircraft and is expected to remain an issue for next generation fighters. LCO arises from the interaction of aerodynamic and structural forces, however the primary contributor to the phenomenon is still unclear. The practical concerns regarding this phenomenon include whether or not ordnance can be safely released and the ability of the aircrew to perform mission-related tasks while in an LCO condition. The focus of this dissertation is the development of control strategies to suppress LCO in aircraft systems. The first contribution of this work (Chapter 2) is the development of a controller consisting of a continuous Robust Integral of the Sign of the Error (RISE) feedback term with a neural network (NN) feedforward term to suppress LCO behavior in an uncertain airfoil system. The second contribution of this work (Chapter 3) is the extension of the development in Chapter 2 to include actuator saturation. Suppression of LCO behavior is achieved through the implementation of an auxiliary error system that features hyperbolic functions and a saturated RISE feedback control structure. Due to the lack of clarity regarding the driving mechanism behind LCO, common practice in literature and in Chapters 2 and 3 is to replicate the symptoms of LCO by including nonlinearities in the wing structure, typically a nonlinear torsional stiffness. To improve the accuracy of the system model a partial differential equation (PDE) model of a flexible wing is derived (see Appendix F) using Hamilton's principle. Chapters 4 and 5 are focused on developing boundary control strategies for regulating the bending and twisting deformations of the derived model. The contribution of Chapter 4 is the construction of a backstepping-based boundary control strategy for a linear PDE model of an aircraft wing. The backstepping-based strategy transforms the original system to a exponentially stable system. A Lyapunov-based stability

  16. Dose and cycle of insecticide applications in the control of malaria

    PubMed Central

    Macdonald, G.; Davidson, G.

    1953-01-01

    The authors first review the doses and cycles of application normally recommended in different parts of the world for DDT, BHC, and dieldrin in controlling malaria, and then discuss the experimental evidence concerning their actual efficacy in the field. The irritant effect of the various insecticides is compared, DDT being found the most irritant and dieldrin the least. BHC appears to be highly irritant when solid, but not when vaporized. The problem of the application of residual insecticides to absorbent surfaces, such as mud, is considered; the wettable powders are generally accepted as the most efficient formulation for such surfaces, but even with these a marked loss in toxicity may occur, requiring higher initial doses and more frequent application than on non-absorbent surfaces. With volatile insecticides, such as BHC, some degree of absorption slows down the loss by volatilization, but at the usual field dosages of 0.1 g and 0.2 g of gamma-BHC per m2 the decline in toxicity is still rapid. Experiments have also shown that mixtures of DDT and BHC may, in some circumstances, combine the initial high kill of the latter with the persistent moderate kill of the former. Considering the insecticidal efficiency needed for the control of malaria, the authors find that most natural circumstances would be met by attaining a mortality-rate of about 65% of mosquitos entering treated shelters; 85% mortality would be suitable for the most severe conditions and 65% mortality for controlling moderate transmission by endophilic mosquitos. PMID:13141131

  17. How do changes in dissolved oxygen concentration influence microbially-controlled phosphorus cycling in stream biofilms?

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Locke, N. A.; Regan, J. M.; Carrick, H. J.; Buda, A. R.; Walter, M. T.

    2014-12-01

    Advances in molecular microbiology techniques (e.g. epi-fluorescent microscopy and PCR) are making it easier to study the influence of specific microorganisms on nutrient transport. Polyphosphate accumulating organisms (PAOs) are commonly used in wastewater treatment plants to remove excess phosphorus (P) from effluent water. PAOs have also been identified in natural settings but their ecological function is not well known. In this study, we tested the hypothesis that PAOs in natural environments would release and accumulate P during anaerobic and aerobic conditions, respectively. We placed stream biofilms in sealed, covered tubs and subjected them to alternating air (aerobic conditions) and N2 gas (anaerobic condition) bubbling for 12 hours each. Four treatments investigated the influence of changing dissolved oxygen on micribially-controlled P cycling: (1) biofilms bubbled continuously with air, (2) biofilms bubbled alternatively with air and N2, (3) biocide treated biofilms bubbled continuously with air, and (4) biocide treated biofilms bubbled alternatively with air and N2. Treatments 3 and 4 serve as abiotic controls to treatments 1 and 2. We analyzed samples every 12 hours for soluble reactive P (SRP), temperature, dissolved oxygen, and pH. We also used fluorescent microscopy (i.e. DAPI staining) and PCR to verify the presence of PAOs in the stream biofilms. SRP results over the course of the experiment support our hypothesis that anaerobic and aerobic stream conditions may impact PAO mediated P release and uptake, respectively in natural environments. The results of these experiments draw attention to the importance of microbiological controls on P mobility in freshwater ecosystems.

  18. The CHR promoter element controls cell cycle-dependent gene transcription and binds the DREAM and MMB complexes

    PubMed Central

    Müller, Gerd A.; Quaas, Marianne; Schümann, Michael; Krause, Eberhard; Padi, Megha; Fischer, Martin; Litovchick, Larisa; DeCaprio, James A.; Engeland, Kurt

    2012-01-01

    Cell cycle-dependent gene expression is often controlled on the transcriptional level. Genes like cyclin B, CDC2 and CDC25C are regulated by cell cycle-dependent element (CDE) and cell cycle genes homology region (CHR) promoter elements mainly through repression in G0/G1. It had been suggested that E2F4 binding to CDE sites is central to transcriptional regulation. However, some promoters are only controlled by a CHR. We identify the DREAM complex binding to the CHR of mouse and human cyclin B2 promoters in G0. Association of DREAM and cell cycle-dependent regulation is abrogated when the CHR is mutated. Although E2f4 is part of the complex, a CDE is not essential but can enhance binding of DREAM. We show that the CHR element is not only necessary for repression of gene transcription in G0/G1, but also for activation in S, G2 and M phases. In proliferating cells, the B-myb-containing MMB complex binds the CHR of both promoters independently of the CDE. Bioinformatic analyses identify many genes which contain conserved CHR elements in promoters binding the DREAM complex. With Ube2c as an example from that screen, we show that inverse CHR sites are functional promoter elements that can bind DREAM and MMB. Our findings indicate that the CHR is central to DREAM/MMB-dependent transcriptional control during the cell cycle. PMID:22064854

  19. The CHR promoter element controls cell cycle-dependent gene transcription and binds the DREAM and MMB complexes.

    PubMed

    Müller, Gerd A; Quaas, Marianne; Schümann, Michael; Krause, Eberhard; Padi, Megha; Fischer, Martin; Litovchick, Larisa; DeCaprio, James A; Engeland, Kurt

    2012-02-01

    Cell cycle-dependent gene expression is often controlled on the transcriptional level. Genes like cyclin B, CDC2 and CDC25C are regulated by cell cycle-dependent element (CDE) and cell cycle genes homology region (CHR) promoter elements mainly through repression in G(0)/G(1). It had been suggested that E2F4 binding to CDE sites is central to transcriptional regulation. However, some promoters are only controlled by a CHR. We identify the DREAM complex binding to the CHR of mouse and human cyclin B2 promoters in G(0). Association of DREAM and cell cycle-dependent regulation is abrogated when the CHR is mutated. Although E2f4 is part of the complex, a CDE is not essential but can enhance binding of DREAM. We show that the CHR element is not only necessary for repression of gene transcription in G(0)/G(1), but also for activation in S, G(2) and M phases. In proliferating cells, the B-myb-containing MMB complex binds the CHR of both promoters independently of the CDE. Bioinformatic analyses identify many genes which contain conserved CHR elements in promoters binding the DREAM complex. With Ube2c as an example from that screen, we show that inverse CHR sites are functional promoter elements that can bind DREAM and MMB. Our findings indicate that the CHR is central to DREAM/MMB-dependent transcriptional control during the cell cycle.

  20. Boolean genetic network model for the control of C. elegans early embryonic cell cycles

    PubMed Central

    2013-01-01

    Background In Caenorhabditis elegans early embryo, cell cycles only have two phases: DNA synthesis and mitosis, which are different from the typical 4-phase cell cycle. Modeling this cell-cycle process into network can fill up the gap in C. elegans cell-cycle study and provide a thorough understanding on the cell-cycle regulations and progressions at the network level. Methods In this paper, C. elegans early embryonic cell-cycle network has been constructed based on the knowledge of key regulators and their interactions from literature studies. A discrete dynamical Boolean model has been applied in computer simulations to study dynamical properties of this network. The cell-cycle network is compared with random networks and tested under several perturbations to analyze its robustness. To investigate whether our proposed network could explain biological experiment results, we have also compared the network simulation results with gene knock down experiment data. Results With the Boolean model, this study showed that the cell-cycle network was stable with a set of attractors (fixed points). A biological pathway was observed in the simulation, which corresponded to a whole cell-cycle progression. The C. elegans network was significantly robust when compared with random networks of the same size because there were less attractors and larger basins than random networks. Moreover, the network was also robust under perturbations with no significant change of the basin size. In addition, the smaller number of attractors and the shorter biological pathway from gene knock down network simulation interpreted the shorter cell-cycle lengths in mutant from the RNAi gene knock down experiment data. Hence, we demonstrated that the results in network simulation could be verified by the RNAi gene knock down experiment data. Conclusions A C. elegans early embryonic cell cycles network was constructed and its properties were analyzed and compared with those of random networks

  1. Controls on diurnal streamflow cycles in a high altitude catchment in the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Mutzner, R.; Weijs, S. V.; Tarolli, P.; Calaf, M.; Oldroyd, H. J.; Parlange, M. B.

    2014-12-01

    The study of streamflow diurnal cycles is of primary importance to understand hydrological processes happening at various spatial scales. In high altitude alpine catchments, streamflow diurnal cycles are typically dominated by snow or icemelt. During a field campaign in the summer 2012 in a small catchment in the Swiss Alps (Val Ferret catchment, draining area of 20.4 km2, mean altitude of 2423 m above sea level (asl), ranging from 1773 m to 3206 m asl, glaciarized area: 2%), we observed streamflow diurnal cycles throughout the season in two monitored sub-basins of the watershed. To study in detail the diurnal cycles, we make use of a wireless network of meteorological stations, time-lapse photography, a fully equipped energy-balance station and water electrical conductivity monitored at the gauging stations. In the first sub-basin, we observed a transition from a snowmelt to an evapotranspiration induced diurnal streamflow cycle. In the second sub-basin, we observed a snowmelt/icemelt dominated diurnal cycle during the entire season due to the presence of a small glacier. Comparisons between icemelt and evapotranspiration cycles showed that the two processes were happening at the same times of day but with a different sign. The amplitude of the icemelt cycle decreased exponentially during the season and was larger than of the amplitude of the evapotranspiration cycle which was relatively constant during the season. A conceptual model was applied to estimate the effect of evapotranspiration on the diurnal streamflow cycle in the icemelt dominated sub-basin. The model makes use of the latent heat measured at the energy balance station, the streamflow loss due to evapotranspiration and the computation of active evapotranspiration areas. Our study suggests that evapotranspiration from the riparian area damps the icemelt-diurnal streamflow cycle resulting in a possible underestimation of glacier mass changes.

  2. Effect of Processing Route on Strain Controlled Low Cycle Fatigue Behavior of Polycrystalline NiAl

    NASA Technical Reports Server (NTRS)

    Rao, K. Bhanu Sankara; Lerch, B. A.; Noebe, R. D.

    1995-01-01

    The present investigation examines the effects of manufacturing process on the total axial strain controlled low cycle fatigue behavior of polycrystalline NiAl at 1000 K, a temperature above the monotonic Brittle-to-Ductile Transition Temperature (BDTT). The nickel aluminide samples were produced by three different processing routes: hot isostatic pressing of pre- alloyed powders, extrusion of prealloyed powders, and extrusion of vacuum induction melted ingots. The LCF behavior of the cast plus extruded material was also determined at room temperature (below the BD77) for comparison to the high temperature data. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were influenced by the alloy preparation technique and the testing temperature. Detailed characterization of the LCF tested samples was conducted by optical and electron microscopy to determine the variations in fracture and deformation modes and to determine any microstructural changes that occurred during LCF testing. The dependence of LCF properties on processing route was rationalized on the basis of starting microstructure, brittle-to-ductile transition temperature, deformation induced changes in the basic microstructure, deformation substructure, and synergistic interaction between the damage modes.

  3. Life-cycle assessment of selected management options for air pollution control residues from waste incineration.

    PubMed

    Fruergaard, Thilde; Hyks, Jiri; Astrup, Thomas

    2010-09-15

    Based on available technology and emission data seven selected management options for air-pollution-control (APC) residues from waste incineration were evaluated by life-cycle assessment (LCA) using the EASEWASTE model. Scenarios were evaluated with respect to both non-toxicity impact categories (e.g. global warming) and toxicity related impact categories (e.g. ecotoxicity and human toxicity). The assessment addressed treatment and final placement of 1 tonne of APC residue in seven scenarios: 1) direct landfilling without treatment (baseline), 2) backfilling in salt mines, 3) neutralization of waste acid, 4) filler material in asphalt, 5) Ferrox stabilization, 6) vitrification, and 7) melting with automobile shredder residues (ASR). The management scenarios were selected as examples of the wide range of different technologies available worldwide while at the same time using realistic technology data. Results from the LCA were discussed with respect to importance of: energy consumption/substitution, material substitution, leaching, air emissions, time horizon aspects for the assessment, and transportation distances. The LCA modeling showed that thermal processes were associated with the highest loads in the non-toxicity categories (energy consumption), while differences between the remaining alternatives were small and generally considered insignificant. In the toxicity categories, all treatment/utilization options were significantly better than direct landfilling without treatment (lower leaching), although the thermal processes had somewhat higher impacts than the others options (air emissions). Transportation distances did not affect the overall ranking of the management alternatives.

  4. Msx2 plays a critical role in lens epithelium cell cycle control

    PubMed Central

    Zhao, Jiang-Yue; Zhuang, Feng-Feng; Wang, Hong-Yan; Wu, Di; Zhang, Jin-Song

    2013-01-01

    AIM To investigate the effects of Msx2 on lens epithelium cell cycle, and evaluate the changes of the proliferation, apoptosis of lens epithelium cells. METHODS Mice lens epithelium cells were cultured and transfected with pEGFP-Msx2 and control. Msx2-deficient mice (Msx2−/−) lens tissue were isolated. Lens tissue and transfected cells were prepared for mRNA extraction using Trizol reagent. CyclinD1 and Prox1 expression were evaluated by real-time RT-PCR. BrdU incorporation and apoptosis rate were investigated by immunofluorescence and flow cytometry analysis. RESULTS After transfected with pEGFP-Msx2, lens epithelium cells failed to incorporate BrdU and anti-phospho-histone-3 immunofluorescence failed to detect cell nuclei which GFP were positive. Msx2 over expression resulted in increasing apoptosis rate in lens epithelium cells. CyclinD1 and Prox1 expression increased significantly in Msx2 knockout mice by real-time RT-PCR quantization and CyclinD1 expression decreased significantly in Msx2 overexpressed cell. CONCLUSION Msx2 has the effect of inhibiting proliferation and differentiation, triggering apoptosis on mice lens epithelium cells. PMID:23826518

  5. Differences in the Tongue Features of Primary Dysmenorrhea Patients and Controls over a Normal Menstrual Cycle

    PubMed Central

    Lee, Haebeom

    2017-01-01

    Background The aims of this study were to investigate the relationships between tongue features and the existence of menstrual pain and to provide basic information regarding the changes in tongue features during a menstrual cycle. Methods This study was conducted at the Kyung Hee University Medical Center. Forty-eight eligible participants aged 20 to 29 years were enrolled and assigned to two groups according to their visual analogue scale (VAS) scores. Group A included 24 females suffering from primary dysmenorrhea (PD) caused by qi stagnation and blood stasis syndrome with VAS ≥ 4. In contrast, Group B included 24 females with few premenstrual symptoms and VAS < 4. All participants completed four visits (menses-follicular-luteal-menses phases), and the tongue images were taken by using a computerized tongue image analysis system (CTIS). Results The results revealed that the tongue coating color value and the tongue coating thickness in the PD group during the menstrual phase were significantly lower than those of the control group (P = 0.031 and P = 0.029, resp.). Conclusions These results suggest that the tongue features obtained from the CTIS may serve as a supplementary means for the differentiation of syndromes and the evaluation of therapeutic effect and prognosis in PD. Trial Registration This trial was registered with Clinical Research Information Service, registration number KCT0001604, registered on 27 August 2015. PMID:28642801

  6. Toward full life cycle control: Adding maintenance measurement to the SEL

    NASA Technical Reports Server (NTRS)

    Rombach, H. Dieter; Ulery, Bradford T.; Valett, Jon D.

    1992-01-01

    Organization-wide measurement of software products and processes is needed to establish full life cycle control over software products. The Software Engineering Laboratory (SEL)--a joint venture between NASA GSFC, the University of Maryland, and Computer Sciences Corporation--started measurement of software development more than 15 years ago. Recently, the measurement of maintenance was added to the scope of the SEL. In this article, the maintenance measurement program is presented as an addition to the already existing and well-established SEL development measurement program and evaluated in terms of its immediate benefits and long-term improvement potential. Immediate benefits of this program for the SEL include an increased understanding of the maintenance domain, the differences and commonalities between development and maintenance, and the cause-effect relationships between development and maintenance. Initial results from a sample maintenance study are presented to substantiate these benefits. The long-term potential of this program includes the use of maintenance baselines to better plan and manage future projects and to improve development and maintenance practices for future projects wherever warranted.

  7. Cyclin F suppresses B-Myb activity to promote cell cycle checkpoint control.

    PubMed

    Klein, Ditte Kjærsgaard; Hoffmann, Saskia; Ahlskog, Johanna K; O'Hanlon, Karen; Quaas, Marianne; Larsen, Brian D; Rolland, Baptiste; Rösner, Heike I; Walter, David; Kousholt, Arne Nedergaard; Menzel, Tobias; Lees, Michael; Johansen, Jens Vilstrup; Rappsilber, Juri; Engeland, Kurt; Sørensen, Claus Storgaard

    2015-01-05

    Cells respond to DNA damage by activating cell cycle checkpoints to delay proliferation and facilitate DNA repair. Here, to uncover new checkpoint regulators, we perform RNA interference screening targeting genes involved in ubiquitylation processes. We show that the F-box protein cyclin F plays an important role in checkpoint control following ionizing radiation. Cyclin F-depleted cells initiate checkpoint signalling after ionizing radiation, but fail to maintain G2 phase arrest and progress into mitosis prematurely. Importantly, cyclin F suppresses the B-Myb-driven transcriptional programme that promotes accumulation of crucial mitosis-promoting proteins. Cyclin F interacts with B-Myb via the cyclin box domain. This interaction is important to suppress cyclin A-mediated phosphorylation of B-Myb, a key step in B-Myb activation. In summary, we uncover a regulatory mechanism linking the F-box protein cyclin F with suppression of the B-Myb/cyclin A pathway to ensure a DNA damage-induced checkpoint response in G2.

  8. Control of continuous irradiation injury on potatoes with daily temperature cycling

    NASA Technical Reports Server (NTRS)

    Tibbitts, T. W.; Bennett, S. M.; Cao, W.

    1990-01-01

    Two controlled-environment experiments were conducted to determine the effects of temperature fluctuations under continuous irradiation on growth and tuberization of two potato (Solanum tuberosum L.) cultivars, Kennebec and Superior. These cultivars had exhibited chlorotic and stunted growth under continuous irradiation and constant temperatures. The plants were grown for 4 weeks in the first experiment and for 6 weeks in the second experiment. Each experiment was conducted under continuous irradiation of 400 micromoles per square meter per second of photosynthetic photon flux and included two temperature treatments: constant 18 degrees C and fluctuating 22 degrees C/14 degrees C on a 12-hour cycle. A common vapor pressure deficit of 0.62 kilopascal was maintained at all temperatures. Plants under constant 18 degrees C were stunted and had chlorotic and abscised leaves and essentially no tuber formation. Plants grown under the fluctuating temperature treatment developed normally, were developing tubers, and had a fivefold or greater total dry weight as compared with those under the constant temperature. These results suggest that a thermoperiod can allow normal plant growth and tuberization in potato cultivars that are unable to develop effectively under continuous irradiation.

  9. Clonally Diverse T Cell Homeostasis Is Maintained by a Common Program of Cell-Cycle Control

    PubMed Central

    Hogan, Thea; Shuvaev, Andrey; Commenges, Daniel; Yates, Andrew; Callard, Robin

    2013-01-01

    Lymphopenia induces T cells to undergo cell divisions as part of a homeostatic response mechanism. The clonal response to lymphopenia is extremely diverse, and it is unknown whether this heterogeneity represents distinct mechanisms of cell-cycle control or whether a common mechanism can account for the diversity. We addressed this question by combining in vivo and mathematical modeling of lymphopenia-induced proliferation (LIP) of two distinct T cell clonotypes. OT-I T cells undergo rapid LIP accompanied by differentiation that superficially resembles Ag-induced proliferation, whereas F5 T cells divide slowly and remain naive. Both F5 and OT-I LIP responses were most accurately described by a single stochastic division model where the rate of cell division was exponentially decreased with increasing cell numbers. The model successfully identified key biological parameters of the response and accurately predicted the homeostatic set point of each clone. Significantly, the model was successful in predicting interclonal competition between OT-I and F5 T cells, consistent with competition for the same resource(s) required for homeostatic proliferation. Our results show that diverse and heterogenous clonal T cell responses can be accounted for by a single common model of homeostasis. PMID:23475214

  10. Control of continuous irradiation injury on potatoes with daily temperature cycling.

    PubMed

    Tibbitts, T W; Bennett, S M; Cao, W

    1990-01-01

    Two controlled-environment experiments were conducted to determine the effects of temperature fluctuations under continuous irradiation on growth and tuberization of two potato (Solanum tuberosum L.) cultivars, Kennebec and Superior. These cultivars had exhibited chlorotic and stunted growth under continuous irradiation and constant temperatures. The plants were grown for 4 weeks in the first experiment and for 6 weeks in the second experiment. Each experiment was conducted under continuous irradiation of 400 micromoles per square meter per second of photosynthetic photon flux and included two temperature treatments: constant 18 degrees C and fluctuating 22 degrees C/14 degrees C on a 12-hour cycle. A common vapor pressure deficit of 0.62 kilopascal was maintained at all temperatures. Plants under constant 18 degrees C were stunted and had chlorotic and abscised leaves and essentially no tuber formation. Plants grown under the fluctuating temperature treatment developed normally, were developing tubers, and had a fivefold or greater total dry weight as compared with those under the constant temperature. These results suggest that a thermoperiod can allow normal plant growth and tuberization in potato cultivars that are unable to develop effectively under continuous irradiation.

  11. Control of continuous irradiation injury on potatoes with daily temperature cycling

    NASA Technical Reports Server (NTRS)

    Tibbitts, T. W.; Bennett, S. M.; Cao, W.

    1990-01-01

    Two controlled-environment experiments were conducted to determine the effects of temperature fluctuations under continuous irradiation on growth and tuberization of two potato (Solanum tuberosum L.) cultivars, Kennebec and Superior. These cultivars had exhibited chlorotic and stunted growth under continuous irradiation and constant temperatures. The plants were grown for 4 weeks in the first experiment and for 6 weeks in the second experiment. Each experiment was conducted under continuous irradiation of 400 micromoles per square meter per second of photosynthetic photon flux and included two temperature treatments: constant 18 degrees C and fluctuating 22 degrees C/14 degrees C on a 12-hour cycle. A common vapor pressure deficit of 0.62 kilopascal was maintained at all temperatures. Plants under constant 18 degrees C were stunted and had chlorotic and abscised leaves and essentially no tuber formation. Plants grown under the fluctuating temperature treatment developed normally, were developing tubers, and had a fivefold or greater total dry weight as compared with those under the constant temperature. These results suggest that a thermoperiod can allow normal plant growth and tuberization in potato cultivars that are unable to develop effectively under continuous irradiation.

  12. Control of Continuous Irradiation Injury on Potatoes with Daily Temperature Cycling 1

    PubMed Central

    Tibbitts, Theodore W.; Bennett, Susan M.; Cao, Weixing

    1990-01-01

    Two controlled-environment experiments were conducted to determine the effects of temperature fluctuations under continuous irradiation on growth and tuberization of two potato (Solanum tuberosum L.) cultivars, Kennebec and Superior. These cultivars had exhibited chlorotic and stunted growth under continuous irradiation and constant temperatures. The plants were grown for 4 weeks in the first experiment and for 6 weeks in the second experiment. Each experiment was conducted under continuous irradiation of 400 micromoles per square meter per second of photosynthetic photon flux and included two temperature treatments: constant 18°C and fluctuating 22°C/14°C on a 12-hour cycle. A common vapor pressure deficit of 0.62 kilopascal was maintained at all temperatures. Plants under constant 18°C were stunted and had chlorotic and abscised leaves and essentially no tuber formation. Plants grown under the fluctuating temperature treatment developed normally, were developing tubers, and had a fivefold or greater total dry weight as compared with those under the constant temperature. These results suggest that a thermoperiod can allow normal plant growth and tuberization in potato cultivars that are unable to develop effectively under continuous irradiation. Images Figure 1 PMID:11537703

  13. Acute physiological response to indoor cycling with and without hydration; case and self-control study.

    PubMed

    Ramos-Jiménez, A; Hernández-Torres, R P; Wall-Medrano, A; Torres-Durán, P V; Juárez-Oropeza, M A; Solis Ceballos, J A

    2013-01-01

    Oral rehydration drinks help maintain physical capacity and hydration during exercise. Evaluate, in a case and self-control study, the effectiveness of three hydration and exercise protocols on work capacity and physical and psychosomatic stress during indoor cycling (InC). 14 middle-aged eutrophic men participated in three controlled randomly and not sequentially hydration (~278 mL 6/c 15 min) and exercise (InC/90 min) protocols: No liquids, plain water, or sports drinks (SD). The response variables were: Body temperature (BT), heart rate (HR), and mean blood pressure (MBP). The covariables: Distance traveled (DT), ergometer resistance (R), body fat (BF), difference in body weight between tests (rBW), and age of the participants. The differences between protocols were evaluated using GLM Repeated Measures, the independence of associations by multiple linear regression. In non-liquids, the subjects showed higher BT, HR, and MBP than when they drank plain water or SD (p < 0.01). Work capacity was the same in the three hydration protocols. BT was the most sensitive variable detected by the hydration status of the subjects. 34%, 99%, and 21% of the associated variance to HR, MBP, and BT was explained by DT + BT, BT + BF, and ΔBW + age + R + DT + BF, respectively. Liquid intake with or without electrolytes does not affect work capacity, and they are equally effective as hydration sources during =?90 min of InC at strong and very strong intensities. Body temperature is the most sensitive variable detected by the subject's hydration status during exercise. Copyright © AULA MEDICA EDICIONES 2013. Published by AULA MEDICA. All rights reserved.

  14. Controls on the speed of spring: challenges for terrestrial carbon cycle models

    NASA Astrophysics Data System (ADS)

    Gu, L.; Fu, Y.

    2010-12-01

    Numerous studies have investigated how climate change will affect the phenology of terrestrial ecosystems, particularly the start of the growing season. However, little attention has been paid to the issue of how fast the growing season will proceed once it has started and what control this speed. Yet the speed of spring, measured by the temporal rate of recovery of plant community photosynthesis, determines annual carbon budget in a fundamental way. Using data from Fluxnet, a global network of eddy covariance flux sites, we studied the recovery rate of canopy photosynthetic capacity across vegetation types. We found that: - Air temperature is the dominant factor that controls the spring recovery (both the timing and the recovery rate) of canopy photosynthesis in northern ecosystems. - However, it is the increasing rate, rather than the absolute value, of daily mean air temperature (other than minimum, maximum air temperature or soil temperature) that determines the peak recovery rate of canopy photosynthetic capacity. - The gross ecosystem productivity in late-half year affects the peak recovery rate of canopy photosynthetic capacity in the following spring, presumably through the influence of substrate supply for metabolism to support new shoot and leaf growth. - Deciduous broad leaf forests and grasslands are more sensitive to temperature change in spring than evergreen needle leaf forests, probably due to the differences in the life history strategy between deciduous and evergreen leaves. These findings suggest new requirements for climate models and point to new processes that should be represented in terrestrial carbon cycle models to improve future predictions of land carbon sinks and sources.

  15. Including Life Cycle Assessment for decision-making in controlling wastewater nutrient removal systems.

    PubMed

    Corominas, Lluís; Larsen, Henrik F; Flores-Alsina, Xavier; Vanrolleghem, Peter A

    2013-10-15

    This paper focuses on the use of Life Cycle Assessment (LCA) to evaluate the performance of seventeen control strategies in wastewater treatment plants (WWTPs). It tackles the importance of using site-specific factors for nutrient enrichment when decision-makers have to select best operating strategies. Therefore, the LCA evaluation is repeated for three different scenarios depending on the limitation of nitrogen (N), phosphorus (P), or both, when evaluating the nutrient enrichment impact in water bodies. The LCA results indicate that for treated effluent discharged into N-deficient aquatic systems (e.g. open coastal areas) the most eco-friendly strategies differ from the ones dealing with discharging into P-deficient (e.g. lakes and rivers) and N&P-deficient systems (e.g. coastal zones). More particularly, the results suggest that strategies that promote increased nutrient removal and/or energy savings present an environmental benefit for N&P and P-deficient systems. This is not the case when addressing N-deficient systems for which the use of chemicals (even for improving N removal efficiencies) is not always beneficial for the environment. A sensitivity analysis on using weighting of the impact categories is conducted to assess how value choices (policy decisions) may affect the management of WWTPs. For the scenarios with only N-limitation, the LCA-based ranking of the control strategies is sensitive to the choice of weighting factors, whereas this is not the case for N&P or P-deficient aquatic systems.

  16. A comparison of calisthenic and cycle exercise training in chronic obstructive pulmonary disease patients: a randomized controlled trial.

    PubMed

    Duruturk, Neslihan; Arıkan, Hulya; Ulubay, Gaye; Tekindal, Mustafa Agah

    2016-01-01

    To compare the effects of calisthenic and cycle exercises with no exercise in chronic obstructive pulmonary disease patients. Forty-seven participants were allocated to either a cycle or calisthenic exercise or control group. Outcome measures, including Saint George Respiratory Questionnaire, pulmonary functions, cardiopulmonary exercise testing, Fitness Testing, and Hospital Anxiety-Depression, Modified Medical Research Council Dyspnea, Fatigue Severity, Fatigue Impact Scales, were performed before and after the intervention. The change in VE/VCO2 significantly differed (p = 0.01) between two exercise groups. Physical fitness, quality of life, anxiety-depression, dyspnea and fatigue changed significantly in exercise groups, with no between-group differences. There were no significant improvements in control group. Calisthenics are as safe and effective as cycle exercise and could be included in comprehensive treatment programs.

  17. Novel control of S-phase of the cell cycle by ubiquitin conjugating enzyme H7

    USDA-ARS?s Scientific Manuscript database

    Timely degradation of regulatory proteins by the ubiquitin proteolytic pathway (UPP) is an established paradigm of cell cycle regulation during the G2/M and G1/S transitions. Less is known about roles for the UPP during S phase. Here we present evidence that dynamic cell cycle dependent changes in l...

  18. The cycle of instability: stress release and fissure flow as controls on gully head retreat

    NASA Astrophysics Data System (ADS)

    Collison, A. J. C.

    2001-01-01

    Gully head and wall retreat has commonly been attributed to fluvial scour and head collapse as a result of soil saturation, sapping or piping. The empirical evidence to substantiate these conceptual models is sparse, however, and often contradictory. This paper explores the hydrological and mechanical controls on gully head and wall stability by modelling the hydrology, stability and elastic deformation of a marl gully complex in Granada Province, south-east Spain. The hydrological and slope-stability simulations show that saturated conditions can be reached only where preferential fissure flow channels water from tension cracks into the base of the gully head, and that vertical or subvertical heads will be stable unless saturation is achieved. Owing to the high unsaturated strengths of marl measured in this research, failure in unsaturated conditions is possible only where the gully head wall is significantly undercut. Head retreat thus requires the formation of either a tension crack or an undercut hollow. Finite-element stress analysis of eroding slopes reveals a build up of shear stress at the gully head base, and a second stress anomaly just upslope of the head wall. Although tension cracks on gully heads have often been attributed to slope unloading, this research provides strong evidence that the so called sapping hollow commonly found in the gully headwall base is also a function of stress release. Although further research is needed, it seems possible that pop out failures in river channels may be caused by the same process. The hydrological analysis shows that, once a tension crack has developed, throughflow velocity in the gully headwall will increase by an order of magnitude, promoting piping and enlargement of this weakened area. It is, therefore, possible to envisage a cycle of gully expansion in which erosion, channel incision or human action unloads the slope below a gully head, leading to stress patterns that account for the tension crack and a

  19. Drosophila neural stem cells: cell cycle control of self-renewal, differentiation, and termination in brain development.

    PubMed

    Reichert, Heinrich

    2011-01-01

    The wealth of neurons that make up the brain are generated through the proliferative activity of neural stem cells during development. This neurogenesis activity involves complex cell cycle control of proliferative self-renewal, differentiation, and termination processes in these cells. Considerable progress has been made in understanding these processes in the neural stem cell-like neuroblasts which generate the brain in the genetic model system Drosophila. Neuroblasts in the developing fly brain generate neurons through repeated series of asymmetrical cell divisions, which balance self-renewal of the neuroblast with generation of differentiated progeny through the segregation of cell fate determinants such as Numb, Prospero, and Brat to the neural progeny. A number of classical cell cycle regulators such as cdc2/CDK1, Polo, Aurora A, and cyclin E are implicated in the control of asymmetric divisions in neuroblasts linking the cell cycle to the asymmetrical division machinery. The cellular and molecular identity of the postmitotic neurons produced by proliferating neuroblasts is influenced by the timing of their exit from the cell cycle through the action of a temporal expression series of transcription factors, which include Hunchback, Kruppel, Pdm, and Castor. This temporal series is also implicated in the control of termination of neuroblast proliferation which is effected by two different cell cycle exit strategies, terminal differentiative division or programmed cell death of the neuroblast. Defects in the asymmetric division machinery which interfere with the termination of proliferation can result in uncontrolled tumorigenic overgrowth. These findings in Drosophila brain development are likely to have general relevance in neural stem cell biology and may apply to cell cycle control in mammalian brain development as well.

  20. Geomorphological control of water tables in a blanket peat landscape: implications for carbon cycling

    NASA Astrophysics Data System (ADS)

    Allott, Tim; Evans, Martin; Lindsay, John; Agnew, Clive; Freer, Jim

    2010-05-01

    Water tables are an important control on carbon cycling and rates of carbon sequestration in peatland systems, and water table depth is therefore a key parameter in carbon models for blanket peat systems. Although there is a wide literature on blanket peat hydrology, including studies which specifically evaluate water table conditions, detailed data on water table behaviour and variability at the landscape scale are sparse. In particular, many British blanket peats are affected by gully erosion and this has been generally assumed to influence water table conditions. However, there has been limited evaluation of this geomomorphological control on peatland water tables. This paper presents results from a project which evaluated water table conditions in the blanket peatlands of the Peak District National Park, UK. A key aim was to quantify the impact of gully erosion on peatland water tables. A detailed programme of water table monitoring was undertaken during 2008/09, involving regular measurements of water table depth in over 530 dipwells at 19 sites across the 47 km2 peatland landscape of the Kinder Scout / Bleaklow area. This included a campaign of regular, simultaneous water table measurements from clusters of dipwells at the main sites, supplemented by continuous (hourly) water table monitoring in selected dipwells. It also included studies to evaluate within-site variation in water table conditions and local water table drawdown effects associated with gully erosion. Results indicate that gully erosion causes water table drawdown through two distinct processes. The first is local water table drawdown immediately adjacent to erosion gullies. This effect is restricted to a zone within 2 m of gully edges, and water tables within the gully edge drawdown zone are approximately 200 mm lower than in the adjacent peatland. The second effect is a more general water table lowering at eroded sites, with median water table depths at heavily eroded sites up to 300 mm lower

  1. Autotrophic and Heterotrophic Controls over Winter Soil Carbon Cycling in a Subalpine Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Monson, R. K.; Scott-Denton, L. E.; Lipson, D. A.; Weintrub, M. N.; Rosenstiel, T. N.; Schmidt, S. K.; Williams, M. W.; Burns, S. P.; Delany, A. E.; Turnipseed, A. A.

    2005-12-01

    Studies were conducted at the Niwot Ridge Ameriflux site to understand wintertime soil carbon cycling and its control over ecosystem respiration. Wintertime respiration in this ecosystem results in the loss of 60-90% of the carbon assimilated the previous growing season. Thus, an understanding of the controls over winter carbon cycling is required to understand controls over the annual carbon budget. Trees were girdled to prevent the transport of photosynthates to the rhizosphere. In plots with non-girdled trees a large mid-winter pulse of sucrose was observed to enter the soil. In plots with girdled trees, no sucrose pulse was observed. Trees of this ecosystem are not photosynthetically active during the winter, leading us to conclude that the sucrose pulse is due to the death of fine roots that had accumulated sucrose the previous autumn. The sucrose pulse is potentially utilized by a novel winter community of microbes. Using DNA fingerprinting we discovered that the dominant isolates from the winter soils were from Jathinobacter, whereas the summer isolates were from Burkholderia. The winter community was capable of high rates of respiration and exponential growth at low temperatures, whereas the summer community was not. Our winter observations also indicated high activity of N-acetyl-C-glucosaminidase, one of the principal enzymes involved in chitin degradation. The presence of such high chitinase activities implicates decomposing fungal biomass as a principle source of CO2 beneath the snow pack. Using a novel in situ, beneath-snow CO2 measurement system, we observed unprecedented Q10 values for winter respiration, being 98 and 8.44 x 104 for the soil next to tree boles or within the open spaces between trees, respectively. These high Q10 values are likely the result of fractional changes in the availability of liquid water below 0°C and responses of microbial biomass to changes in the liquid water fraction. Using six-years of eddy covariance data, we showed

  2. Live-cell monitoring of periodic gene expression in synchronous human cells identifies Forkhead genes involved in cell cycle control.

    PubMed

    Grant, Gavin D; Gamsby, Joshua; Martyanov, Viktor; Brooks, Lionel; George, Lacy K; Mahoney, J Matthew; Loros, Jennifer J; Dunlap, Jay C; Whitfield, Michael L

    2012-08-01

    We developed a system to monitor periodic luciferase activity from cell cycle-regulated promoters in synchronous cells. Reporters were driven by a minimal human E2F1 promoter with peak expression in G1/S or a basal promoter with six Forkhead DNA-binding sites with peak expression at G2/M. After cell cycle synchronization, luciferase activity was measured in live cells at 10-min intervals across three to four synchronous cell cycles, allowing unprecedented resolution of cell cycle-regulated gene expression. We used this assay to screen Forkhead transcription factors for control of periodic gene expression. We confirmed a role for FOXM1 and identified two novel cell cycle regulators, FOXJ3 and FOXK1. Knockdown of FOXJ3 and FOXK1 eliminated cell cycle-dependent oscillations and resulted in decreased cell proliferation rates. Analysis of genes regulated by FOXJ3 and FOXK1 showed that FOXJ3 may regulate a network of zinc finger proteins and that FOXK1 binds to the promoter and regulates DHFR, TYMS, GSDMD, and the E2F binding partner TFDP1. Chromatin immunoprecipitation followed by high-throughput sequencing analysis identified 4329 genomic loci bound by FOXK1, 83% of which contained a FOXK1-binding motif. We verified that a subset of these loci are activated by wild-type FOXK1 but not by a FOXK1 (H355A) DNA-binding mutant.

  3. The Relations of Locus of Control and Social Support to Life-Cycle Related Needs of Widows.

    ERIC Educational Resources Information Center

    Lowenstein, Ariela; Rosan, Aaron

    1995-01-01

    Widows of varying ages (n=246) in urban Israel were investigated to examine the effects of widowhood-related needs along the life cycle and variables hypothesized to be related to it. Findings support previous research regarding the role of locus of control as a support mobilizer. Discusses importance of personal as well as environmental resources…

  4. The impact of premature progesterone rise on the outcome of intrauterine insemination cycles with controlled ovarian hyperstimulation in unexplained infertility.

    PubMed

    Mutlu, Mehmet Firat; Erdem, Mehmet; Erdem, Ahmet; Mutlu, Ilknur; Guler, Ismail; Demirdağ, Erhan

    2016-08-01

    To ascertain the incidence of premature progesterone P rise and its impact on outcomes in controlled ovarian hyperstimulation and intrauterine insemination (COH-IUI) cycles, and also to identify variables related with premature P rise. Four hundred sixty cycles of 460 couples with unexplained infertility having COH-IUI treatment with a starting dose of 75IU recombinant FSH enrolled in this prospective study. Serum P levels were determined on the day of hCG trigger. Premature P rise was defined as progesterone ≥1ng/mL. The primary outcome measure was live birth per cycle with regard to P levels of ≥1ng/mL and ≥1.5ng/mL. Secondary outcome measures were cycle characteristics associated with P rise. The incidence of premature P rise was 22.0%. P levels on hCG day were significantly lower in cycles with live birth as compared to cycles without live birth 0.49±0.51 vs. 0.73±0.82ng/mL. Live birth rates were significantly lower in cycles with hCG day P levels ≥1.0ng/mL (%7.9 vs. %22.6) and ≥1.5ng/mL (%6.4 vs. %20.8). Among age, number of dominant follicles, estradiol, LH and P levels on the day of hCG trigger, it was found that P levels was the only significant variable to predict live birth on multivariate analysis. The number of dominant follicles on hCG day and premature LH surge were the only significant variables related with premature P rise. Premature P is a frequent feature of COH-IUI cycles and associated with decreased live birth rates. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Results of chopper-controlled discharge life cycling studies on lead acid batteries

    NASA Technical Reports Server (NTRS)

    Ewashinka, J. G.; Sidik, S. M.

    1982-01-01

    A group of 108 state of the art nominally 6 volt lead acid batteries were tested in a program of one charge/discharge cycle per day for over two years or to ultimate battery failure. The primary objective was to determine battery cycle life as a function of depth of discharge (25 to 75 percent), chopper frequency (100 to 1000 Hz), duty cycle (25 to 87.5 percent), and average discharge current (20 to 260 A). The secondary objective was to determine the types of battery failure modes, if any, were due to the above parameters. The four parameters above were incorporated in a statistically designed test program.

  6. "Annual cycle of availability of fruits", a geographical bound concern in planning for control of diabetes mellitus.

    PubMed

    Wiwanitkit, Viroj

    2011-01-01

    The glycemic control of diabetic patients seems to be a simple preventive practice but hard-to-do procedure for the diabetic patients. The unsuccessful control can be frequently seen. In this specific paper, the author hereby reports and discusses on "annual cycle of availability of fruits" and the observed poorly controlled diabetes from a setting in tropical Asia. This report can imply the geographical bound concern in planning for control of diabetes mellitus. Copyright © 2010 Diabetes India. Published by Elsevier Ltd. All rights reserved.

  7. Effectiveness and equity impacts of town-wide cycling initiatives in England: a longitudinal, controlled natural experimental study.

    PubMed

    Goodman, Anna; Panter, Jenna; Sharp, Stephen J; Ogilvie, David

    2013-11-01

    Cycling confers health and environmental benefits, but few robust studies have evaluated large-scale programmes to promote cycling. In England, recent years have seen substantial, town-wide cycling initiatives in six Cycling Demonstration Towns (funded 2005-2011) and 12 Cycling Cities and Towns (funded 2008-2011). The initiatives involved mixtures of capital investment (e.g. cycle lanes) and revenue investment (e.g. cycle training), tailored to each town. This controlled before-after natural experimental study used English census data to examine impacts on the prevalence of travelling to work by bicycle and other modes, comparing changes in the intervention towns with changes in three comparison groups (matched towns, unfunded towns and a national comparison group). We also compared effects between more and less deprived areas, and used random-effects meta-analysis to compare intervention effects between towns. Among 1.3 million commuters in 18 intervention towns, we found that the prevalence of cycling to work rose from 5.8% in 2001 to 6.8% in 2011. This represented a significant increase relative to all three comparison groups (e.g. +0.69 (95% CI 0.60,0.77) percentage points for intervention vs. matched towns). Walking to work also increased significantly compared with comparison towns, while driving to work decreased and public transport use was unchanged. These effects were observed across all fifths of area deprivation, with larger relative changes in deprived areas. There was substantial variation in effect sizes between towns, however, and the average town-level effect on cycling was non-significant (+0.29 (-0.26,0.84) percentage points for intervention vs. matched towns). We conclude that to date, cycling to work has increased (and driving to work decreased) in the intervention towns, in a relatively equitable manner. The variation in effects between towns indicates uncertainty regarding the likely impact of comparable investment in future towns

  8. Carbon dioxide control costs for gasification combined-cycle plants in the United States

    SciTech Connect

    Brown, D.R.; Humphreys, K.K.; Vail, L.W.

    1993-06-01

    This study focused on evaluating the cost of recovering CO{sub 2} from coal gasification, combined-cycle (GCC) power plants and transporting the CO{sub 2} in pipelines for disposal in deep ocean water, depleted oil and gas reservoirs, or aquifers. Other fuels and conversion technologies were not evaluated. Technical feasibility, environmental acceptability, and other implementation issues were not addressed in detail. Ocean disposal of CO{sub 2} offers essentially unlimited capacity, but is distant from most US coal-fired power plants and presents environmental concerns at the disposal point. Depleted oil and gas reservoirs are also distant from most US coal-fired power plants and have a more limited disposal capacity,, but were calculated to have a potential capacity more than double that required to dispose of all CO{sub 2} from 830 GCC power plants (380-mwe each) for a period of 40 years. The existence of oil and gas reservoirs provides ``proof`` of the long-term CO{sub 2} confinement potential in these formations. In contrast, aquifer disposal is believed to be significantly riskier. Key concerns are lack of geologic knowledge at depths adequate for CO{sub 2} disposal; uncertainty about geochemical impacts from decreased water pH; and long-term confinement, which is unproven for non-petroleum formations. Carbon dioxide recovery at GCC plants increased the levelized energy cost (LEC) by about one third relative to a reference GCC plant without CO{sub 2} recovery. The transmission distance is the key factor affecting total CO{sub 2} control costs.

  9. Control of the annual cycle in birds: endocrine constraints and plasticity in response to ecological variability.

    PubMed

    Dawson, Alistair

    2008-05-12

    This paper reviews information from ecological and physiological studies to assess how extrinsic factors can modulate intrinsic physiological processes. The annual cycle of birds is made up of a sequence of life-history stages: breeding, moult and migration. Each stage has evolved to occur at the optimum time and to last for the whole duration of time available. Some species have predictable breeding seasons, others are more flexible and some breed opportunistically in response to unpredictable food availability. Photoperiod is the principal environmental cue used to time each stage, allowing birds to adapt their physiology in advance of predictable environmental changes. Physiological (neuroendocrine and endocrine) plasticity allows non-photoperiodic cues to modulate timing to enable individuals to cope with, and benefit from, short-term environmental variability. Although the timing and duration of the period of full gonadal maturation is principally controlled by photoperiod, non-photoperiodic cues, such as temperature, rainfall or food availability, could potentially modulate the exact time of breeding either by fine-tuning the time of egg-laying within the period of full gonadal maturity or, more fundamentally, by modulating gonadal maturation and/or regression. The timing of gonadal regression affects the time of the start of moult, which in turn may affect the duration of the moult. There are many areas of uncertainty. Future integrated studies are required to assess the scope for flexibility in life-history strategies as this will have a critical bearing on whether birds can adapt sufficiently rapidly to anthropogenic environmental changes, in particular climate change.

  10. Late - Cycle Injection of Air/Oxygen - Enriched Air for Diesel Exhaust Emissions Control

    SciTech Connect

    Mather, Daniel

    2000-08-20

    Reduce the ''Engine Out'' particulates using the ''In Cylinder'' technique of late cycle auxiliary gas injection (AGI). Reduce the ''Engine Out'' NOx by combining AGI with optimization of fuel injection parameters. Maintain or Improve the Fuel Efficiency.

  11. Regulation of RNA polymerase II activity by CTD phosphorylation and cell cycle control.

    PubMed

    Oelgeschläger, Thomas

    2002-02-01

    The carboxyl-terminal domain (CTD) of the largest subunit of mammalian RNA polymerase II (RNAP II) consists of 52 repeats of a consensus heptapeptide and is subject to phosphorylation and dephosphorylation events during each round of transcription. RNAP II activity is regulated during the cell cycle and cell cycle-dependend changes in RNAP II activity correlate well with CTD phosphorylation. In addition, global changes in the CTD phosphorylation status are observed in response to mitogenic or cytostatic signals such as growth factors, mitogens and DNA-damaging agents. Several CTD kinases are members of the cyclin-dependent kinase (CDK) superfamily and associate with transcription initiation complexes. Other CTD kinases implicated in cell cycle regulation include the mitogen-activated protein kinases ERK-1/2 and the c-Abl tyrosine kinase. These observations suggest that reversible RNAP II CTD phosphorylation may play a key role in linking cell cycle regulatory events to coordinated changes in transcription.

  12. Wagging the dogma; tissue-specific cell cycle control in the mouse embryo.

    PubMed

    Pagano, Michele; Jackson, Peter K

    2004-09-03

    The family of cyclin-dependent kinases (Cdks) lies at the core of the machinery that drives the cell division cycle. Studies in cultured mammalian cells have provided insight into the cellular functions of many Cdks. Recent Cdk and cyclin knockouts in the mouse show that the functions of G1 cell cycle regulatory genes are often essential only in specific cell types, pointing to our limited understanding of tissue-specific expression, redundancy, and compensating mechanisms in the Cdk network.

  13. The ubiquitin proteasome system - implications for cell cycle control and the targeted treatment of cancer.

    PubMed

    Bassermann, Florian; Eichner, Ruth; Pagano, Michele

    2014-01-01

    Two families of E3 ubiquitin ligases are prominent in cell cycle regulation and mediate the timely and precise ubiquitin-proteasome-dependent degradation of key cell cycle proteins: the SCF (Skp1/Cul1/F-box protein) complex and the APC/C (anaphase promoting complex or cyclosome). While certain SCF ligases drive cell cycle progression throughout the cell cycle, APC/C (in complex with either of two substrate recruiting proteins: Cdc20 and Cdh1) orchestrates exit from mitosis (APC/C(Cdc20)) and establishes a stable G1 phase (APC/C(Cdh1)). Upon DNA damage or perturbation of the normal cell cycle, both ligases are involved in checkpoint activation. Mechanistic insight into these processes has significantly improved over the last ten years, largely due to a better understanding of APC/C and the functional characterization of multiple F-box proteins, the variable substrate recruiting components of SCF ligases. Here, we review the role of SCF- and APC/C-mediated ubiquitylation in the normal and perturbed cell cycle and discuss potential clinical implications of SCF and APC/C functions. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. The ubiquitin proteasome system – Implications for cell cycle control and the targeted treatment of cancer

    PubMed Central

    Bassermann, Florian; Eichner, Ruth; Pagano, Michele

    2013-01-01

    Two families of E3 ubiquitin ligases are prominent in cell cycle regulation and mediate the timely and precise ubiquitin-proteasome-dependent degradation of key cell cycle proteins: the SCF (Skp1/Cul1/F-box protein) complex and the APC/C (Anaphase Promoting Complex or Cyclosome). While certain SCF ligases drive cell cycle progression throughout the cell cycle, APC/C (in complex with either of two substrate recruiting proteins: Cdc20 and Cdh1) orchestrates exit from mitosis (APC/CCdc20) and establishes a stable G1 phase (APC/CCdh1). Upon DNA damage or perturbation of the normal cell cycle, both ligases are involved in checkpoint activation. Mechanistic insight into these processes has significantly improved over the last ten years, largely due to a better understanding of APC/C and the functional characterization of multiple F-box proteins, the variable substrate recruiting components of SCF ligases. Here, we review the role of SCF- and APC/C-mediated ubiquitylation in the normal and perturbed cell cycle and discuss potential clinical implications of SCF and APC/C functions. PMID:23466868

  15. Cell cycle control as a basis for cancer chemoprevention through dietary agents

    PubMed Central

    Meeran, Syed Musthapa; Katiyar, Santosh Kumar

    2008-01-01

    The development of cancer is associated with disorders in the regulation of the cell cycle. The purpose of this review is to briefly summarize the known sequence of events that regulate cell cycle progression with an emphasis on the checkpoints and the mechanisms cell employ to insure DNA stability in the face of genotoxic stress. Key transitions in the cell cycle are regulated by the activities of various protein kinase complexes composed of cyclin and cyclin-dependent kinases (CDK) molecules. The cyclins are CDK binding partners which are required for kinase activity and their protein levels are intimately linked to the cell cycle stage. CDK activity can be regulated by other mechanisms, such as phosphorylation events, that may contribute to deregulation of cell cycle and the development of cancer. While fruits and vegetables are recommended for prevention of cancer, their active ingredients and mechanisms of action are less well understood. Here, we briefly present evidence that dietary agents identified from fruits and vegetables can act to modulate the effects of deregulated cell cycle checkpoints, and that this may contribute to the prevention of cancer. The agents include apigenin (celery, parsley), curcumin (turmeric), (−)-epigallocatechin-3-gallate (green tea), resveratrol (red grape, peanuts and berries), genistein (soybean), and silymarin (milk thistle). The teachings of Hippocrates are still true “let food be thy medicine and medicine be thy food”. PMID:17981702

  16. Orogenic inheritance and continental breakup: Wilson Cycle-control on rift and passive margin evolution

    NASA Astrophysics Data System (ADS)

    Schiffer, C.; Petersen, K. D.

    2016-12-01

    Rifts often develop along suture zones between previously collided continents, as part of the Wilson cycle. The North Atlantic is such an example, formed where Pangaea broke apart along Caledonian and Variscan sutures. Dipping upper mantle structures in E. Greenland and Scotland, have been interpreted as fossil subduction zones and the seismic signature indicates the presence of eclogite and serpentinite. We speculate that this orogenic material may impose a rheological control upon post-orogenic extension and we use thermo-mechanical modelling to explore such effects. Our model includes the following features: 1) Crustal thickness anomalies, 2) Eclogitised mafic crust emplaced in the mantle lithosphere, and 3) Hydrated mantle peridotite (serpentinite) formed in a pre-rift subduction setting. Our models indicate that the inherited structures control the location and the structural and magmatic evolution of the rift. Rifting of thin initial crust allows for relatively large amounts of serpentinite to be preserved within the uppermost mantle. This facilitates rapid continental breakup and serpentinite exhumation. Magmatism does not occur before continental breakup. Rifts in thicker crust preserve little or no serpentinite and thinning is more focused in the mantle lithosphere, rather than in the crust. Continental breakup is therefore preceded by magmatism. This implies that pre-rift orogenic properties may determine whether magma-poor or magma-rich conjugate margins are formed. Our models show that inherited orogenic eclogite and serpentinite are deformed and partially emplaced either as dipping structures within the lithospheric mantle or at the base of the thinned continental crust. The former is consistent with dipping sub-Moho reflectors often observed in passive margins. The latter provides an alternative interpretation of `lower crustal bodies' which are often regarded as igneous bodies. An additional implication of our models is that serpentinite, often

  17. p27kip1 controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability

    PubMed Central

    Fabris, Linda; Berton, Stefania; Pellizzari, Ilenia; Segatto, Ilenia; D’Andrea, Sara; Armenia, Joshua; Bomben, Riccardo; Schiappacassi, Monica; Gattei, Valter; Philips, Mark R.; Vecchione, Andrea; Belletti, Barbara; Baldassarre, Gustavo

    2015-01-01

    The cyclin-dependent kinase (CDK) inhibitor p27kip1 is a critical regulator of the G1/S-phase transition of the cell cycle and also regulates microtubule (MT) stability. This latter function is exerted by modulating the activity of stathmin, an MT-destabilizing protein, and by direct binding to MTs. We recently demonstrated that increased proliferation in p27kip1-null mice is reverted by concomitant deletion of stathmin in p27kip1/stathmin double-KO mice, suggesting that a CDK-independent function of p27kip1 contributes to the control of cell proliferation. Whether the regulation of MT stability by p27kip1 impinges on signaling pathway activation and contributes to the decision to enter the cell cycle is largely unknown. Here, we report that faster cell cycle entry of p27kip1-null cells was impaired by the concomitant deletion of stathmin. Using gene expression profiling coupled with bioinformatic analyses, we show that p27kip1 and stathmin conjunctly control activation of the MAPK pathway. From a molecular point of view, we observed that p27kip1, by controlling MT stability, impinges on H-Ras trafficking and ubiquitination levels, eventually restraining its full activation. Our study identifies a regulatory axis controlling the G1/S-phase transition, relying on the regulation of MT stability by p27kip1 and finely controlling the spatiotemporal activation of the Ras-MAPK signaling pathway. PMID:26512117

  18. p27kip1 controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability.

    PubMed

    Fabris, Linda; Berton, Stefania; Pellizzari, Ilenia; Segatto, Ilenia; D'Andrea, Sara; Armenia, Joshua; Bomben, Riccardo; Schiappacassi, Monica; Gattei, Valter; Philips, Mark R; Vecchione, Andrea; Belletti, Barbara; Baldassarre, Gustavo

    2015-11-10

    The cyclin-dependent kinase (CDK) inhibitor p27(kip1) is a critical regulator of the G1/S-phase transition of the cell cycle and also regulates microtubule (MT) stability. This latter function is exerted by modulating the activity of stathmin, an MT-destabilizing protein, and by direct binding to MTs. We recently demonstrated that increased proliferation in p27(kip1)-null mice is reverted by concomitant deletion of stathmin in p27(kip1)/stathmin double-KO mice, suggesting that a CDK-independent function of p27(kip1) contributes to the control of cell proliferation. Whether the regulation of MT stability by p27(kip1) impinges on signaling pathway activation and contributes to the decision to enter the cell cycle is largely unknown. Here, we report that faster cell cycle entry of p27(kip1)-null cells was impaired by the concomitant deletion of stathmin. Using gene expression profiling coupled with bioinformatic analyses, we show that p27(kip1) and stathmin conjunctly control activation of the MAPK pathway. From a molecular point of view, we observed that p27(kip1), by controlling MT stability, impinges on H-Ras trafficking and ubiquitination levels, eventually restraining its full activation. Our study identifies a regulatory axis controlling the G1/S-phase transition, relying on the regulation of MT stability by p27(kip1) and finely controlling the spatiotemporal activation of the Ras-MAPK signaling pathway.

  19. Plasma-Based Generation and Control of a Single Few-Cycle High-Energy Ultrahigh-Intensity Laser Pulse

    NASA Astrophysics Data System (ADS)

    Tamburini, M.; Di Piazza, A.; Liseykina, T. V.; Keitel, C. H.

    2014-07-01

    A laser-boosted relativistic solid-density paraboloidal foil is known to efficiently reflect and focus a counterpropagating laser pulse. Here we show that in the case of an ultrarelativistic counterpropagating pulse, a high-energy and ultrahigh-intensity reflected pulse can be more effectively generated by a relatively slow and heavy foil than by a fast and light one. This counterintuitive result is explained with the larger reflectivity of a heavy foil, which compensates for its lower relativistic Doppler factor. Moreover, since the counterpropagating pulse is ultrarelativistic, the foil is abruptly dispersed and only the first few cycles of the counterpropagating pulse are reflected. Our multidimensional particle-in-cell simulations show that even few-cycle counterpropagating laser pulses can be further shortened (both temporally and in the number of laser cycles) with pulse amplification. A single few-cycle, multipetawatt laser pulse with several joules of energy and with a peak intensity exceeding 1023 W/cm2 can be generated already employing next-generation high-power laser systems. In addition, the carrier-envelope phase of the generated few-cycle pulse can be tuned provided that the carrier-envelope phase of the initial counterpropagating pulse is controlled.

  20. Analysis of supercritical CO{sub 2} cycle control strategies and dynamic response for Generation IV Reactors.

    SciTech Connect

    Moisseytsev, A.; Sienicki, J. J.

    2011-04-12

    The analysis of specific control strategies and dynamic behavior of the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle has been extended to the two reactor types selected for continued development under the Generation IV Nuclear Energy Systems Initiative; namely, the Very High Temperature Reactor (VHTR) and the Sodium-Cooled Fast Reactor (SFR). Direct application of the standard S-CO{sub 2} recompression cycle to the VHTR was found to be challenging because of the mismatch in the temperature drop of the He gaseous reactor coolant through the He-to-CO{sub 2} reactor heat exchanger (RHX) versus the temperature rise of the CO{sub 2} through the RHX. The reference VHTR features a large temperature drop of 450 C between the assumed core outlet and inlet temperatures of 850 and 400 C, respectively. This large temperature difference is an essential feature of the VHTR enabling a lower He flow rate reducing the required core velocities and pressure drop. In contrast, the standard recompression S-CO{sub 2} cycle wants to operate with a temperature rise through the RHX of about 150 C reflecting the temperature drop as the CO{sub 2} expands from 20 MPa to 7.4 MPa in the turbine and the fact that the cycle is highly recuperated such that the CO{sub 2} entering the RHX is effectively preheated. Because of this mismatch, direct application of the standard recompression cycle results in a relatively poor cycle efficiency of 44.9%. However, two approaches have been identified by which the S-CO{sub 2} cycle can be successfully adapted to the VHTR and the benefits of the S-CO{sub 2} cycle, especially a significant gain in cycle efficiency, can be realized. The first approach involves the use of three separate cascaded S-CO{sub 2} cycles. Each S-CO{sub 2} cycle is coupled to the VHTR through its own He-to-CO{sub 2} RHX in which the He temperature is reduced by 150 C. The three respective cycles have efficiencies of 54, 50, and 44%, respectively, resulting in a net cycle

  1. Translation-independent circadian control of the cell cycle in a unicellular photosynthetic eukaryote.

    PubMed

    Miyagishima, Shin-ya; Fujiwara, Takayuki; Sumiya, Nobuko; Hirooka, Shunsuke; Nakano, Akihiko; Kabeya, Yukihiro; Nakamura, Mami

    2014-05-08

    Circadian rhythms of cell division have been observed in several lineages of eukaryotes, especially photosynthetic unicellular eukaryotes. However, the mechanism underlying the circadian regulation of the cell cycle and the nature of the advantage conferred remain unknown. Here, using the unicellular red alga Cyanidioschyzon merolae, we show that the G1/S regulator RBR-E2F-DP complex links the G1/S transition to circadian rhythms. Time-dependent E2F phosphorylation promotes the G1/S transition during subjective night and this phosphorylation event occurs independently of cell cycle progression, even under continuous dark or when cytosolic translation is inhibited. Constitutive expression of a phospho-mimic of E2F or depletion of RBR unlinks cell cycle progression from circadian rhythms. These transgenic lines are exposed to higher oxidative stress than the wild type. Circadian inhibition of cell cycle progression during the daytime by RBR-E2F-DP pathway likely protects cells from photosynthetic oxidative stress by temporally compartmentalizing photosynthesis and cell cycle progression.

  2. Optical properties of the breast during spontaneous and birth control pill-mediated menstrual cycles.

    PubMed

    Stahel, Michèle C; Wolf, Martin; Baños, Ana; Hornung, R

    2009-11-01

    Mastodynia is correlated with the menstrual cycle. Using frequency-domain near-infrared spectroscopy (FD-NIRS), we investigated changes in breast perfusion in women who were or were not using hormonal contraception. Healthy volunteers, on or not on hormonal contraception, were examined. Optical properties were measured in all quadrants of both breasts, and physiological parameters were calculated. Measurements were repeated every other day during one complete menstrual cycle. Measurements were comparable in all quadrants. Data remained unchanged during the entire cycle in patients using hormonal contraception. However, a biphasic variation of deoxyhemoglobin, oxyhemoglobin, total hemoglobin (tHb), and water content (H(2)O) was observed in women not using contraception. tHb and H(2)O distinctly increased during the ovulation period and remained elevated throughout the luteal phase. It was concluded that FD-NIRS allows accurate measurement of optical properties of human breasts. As opposed to the menstrual cycles of persons using oral contraception, spontaneous menstrual cycles exhibit biphasic variations of tissue perfusion parameters. These findings are important for the investigation of mastodynia.

  3. Follicular flushing in natural cycle IVF does not affect the luteal phase - a prospective controlled study.

    PubMed

    von Wolff, M; Kohl Schwartz, A; Stute, P; Fäh, M; Otti, G; Schürch, R; Rohner, S

    2017-07-01

    In contrast to multifollicular IVF, follicular flushing seems to increase the efficacy of monofollicular IVF treatments such as natural cycle IVF (NC-IVF). However, because follicular flushing causes loss of granulosa cells, it might negatively affect luteal phase length and endocrine function of the luteal body. A prospective cohort Phase II study was performed in 24 women undergoing NC-IVF. Women underwent a reference cycle with human chorionic gonadotrophin-induced ovulation without follicle aspiration and analysis of the length of the luteal phase and luteal concentrations of progesterone and oestradiol. In addition, they underwent a NC-IVF cycle which was performed identically but follicles were aspirated and flushed three times. The luteal phase was shorter in 29.2%, equal in 16.7% and longer in 50.0% of cases following flushing of the follicles. Overall, neither difference in luteal phase length was significant [median duration (interquartile range) in reference cycle: 13 (12; 14.5), IVF (flushing) cycle: 14 (12.5; 14.5), median difference (95% CI): 0.5 (-0.5 to 1.5)] nor median progesterone and oestradiol concentrations. In conclusion, follicular flushing in NC-IVF affects neither the length of the luteal phase nor the luteal phase concentrations of progesterone and oestradiol, questioning the need for luteal phase supplementation. Copyright © 2017 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  4. Stable cycling of double-walled silicon nanotube battery anodes through solid-electrolyte interphase control.

    PubMed

    Wu, Hui; Chan, Gerentt; Choi, Jang Wook; Ryu, Ill; Yao, Yan; McDowell, Matthew T; Lee, Seok Woo; Jackson, Ariel; Yang, Yuan; Hu, Liangbing; Cui, Yi

    2012-03-25

    Although the performance of lithium ion-batteries continues to improve, their energy density and cycle life remain insufficient for applications in consumer electronics, transport and large-scale renewable energy storage. Silicon has a large charge storage capacity and this makes it an attractive anode material, but pulverization during cycling and an unstable solid-electrolyte interphase has limited the cycle life of silicon anodes to hundreds of cycles. Here, we show that anodes consisting of an active silicon nanotube surrounded by an ion-permeable silicon oxide shell can cycle over 6,000 times in half cells while retaining more than 85% of their initial capacity. The outer surface of the silicon nanotube is prevented from expansion by the oxide shell, and the expanding inner surface is not exposed to the electrolyte, resulting in a stable solid-electrolyte interphase. Batteries containing these double-walled silicon nanotube anodes exhibit charge capacities approximately eight times larger than conventional carbon anodes and charging rates of up to 20C (a rate of 1C corresponds to complete charge or discharge in one hour).

  5. Cell Cycle Constraints and Environmental Control of Local DNA Hypomethylation in α-Proteobacteria.

    PubMed

    Ardissone, Silvia; Redder, Peter; Russo, Giancarlo; Frandi, Antonio; Fumeaux, Coralie; Patrignani, Andrea; Schlapbach, Ralph; Falquet, Laurent; Viollier, Patrick H

    2016-12-01

    Heritable DNA methylation imprints are ubiquitous and underlie genetic variability from bacteria to humans. In microbial genomes, DNA methylation has been implicated in gene transcription, DNA replication and repair, nucleoid segregation, transposition and virulence of pathogenic strains. Despite the importance of local (hypo)methylation at specific loci, how and when these patterns are established during the cell cycle remains poorly characterized. Taking advantage of the small genomes and the synchronizability of α-proteobacteria, we discovered that conserved determinants of the cell cycle transcriptional circuitry establish specific hypomethylation patterns in the cell cycle model system Caulobacter crescentus. We used genome-wide methyl-N6-adenine (m6A-) analyses by restriction-enzyme-cleavage sequencing (REC-Seq) and single-molecule real-time (SMRT) sequencing to show that MucR, a transcriptional regulator that represses virulence and cell cycle genes in S-phase but no longer in G1-phase, occludes 5'-GANTC-3' sequence motifs that are methylated by the DNA adenine methyltransferase CcrM. Constitutive expression of CcrM or heterologous methylases in at least two different α-proteobacteria homogenizes m6A patterns even when MucR is present and affects promoter activity. Environmental stress (phosphate limitation) can override and reconfigure local hypomethylation patterns imposed by the cell cycle circuitry that dictate when and where local hypomethylation is instated.

  6. Cell Cycle Constraints and Environmental Control of Local DNA Hypomethylation in α-Proteobacteria

    PubMed Central

    Russo, Giancarlo; Frandi, Antonio; Patrignani, Andrea

    2016-01-01

    Heritable DNA methylation imprints are ubiquitous and underlie genetic variability from bacteria to humans. In microbial genomes, DNA methylation has been implicated in gene transcription, DNA replication and repair, nucleoid segregation, transposition and virulence of pathogenic strains. Despite the importance of local (hypo)methylation at specific loci, how and when these patterns are established during the cell cycle remains poorly characterized. Taking advantage of the small genomes and the synchronizability of α-proteobacteria, we discovered that conserved determinants of the cell cycle transcriptional circuitry establish specific hypomethylation patterns in the cell cycle model system Caulobacter crescentus. We used genome-wide methyl-N6-adenine (m6A-) analyses by restriction-enzyme-cleavage sequencing (REC-Seq) and single-molecule real-time (SMRT) sequencing to show that MucR, a transcriptional regulator that represses virulence and cell cycle genes in S-phase but no longer in G1-phase, occludes 5’-GANTC-3’ sequence motifs that are methylated by the DNA adenine methyltransferase CcrM. Constitutive expression of CcrM or heterologous methylases in at least two different α-proteobacteria homogenizes m6A patterns even when MucR is present and affects promoter activity. Environmental stress (phosphate limitation) can override and reconfigure local hypomethylation patterns imposed by the cell cycle circuitry that dictate when and where local hypomethylation is instated. PMID:27997543

  7. Proposed megakaryocytic regulon of p53: the genes engaged to control cell cycle and apoptosis during megakaryocytic differentiation.

    PubMed

    Apostolidis, Pani A; Lindsey, Stephan; Miller, William M; Papoutsakis, Eleftherios T

    2012-06-15

    During endomitosis, megakaryocytes undergo several rounds of DNA synthesis without division leading to polyploidization. In primary megakaryocytes and in the megakaryocytic cell line CHRF, loss or knock-down of p53 enhances cell cycling and inhibits apoptosis, leading to increased polyploidization. To support the hypothesis that p53 suppresses megakaryocytic polyploidization, we show that stable expression of wild-type p53 in K562 cells (a p53-null cell line) attenuates the cells' ability to undergo polyploidization during megakaryocytic differentiation due to diminished DNA synthesis and greater apoptosis. This suggested that p53's effects during megakaryopoiesis are mediated through cell cycle- and apoptosis-related target genes, possibly by arresting DNA synthesis and promoting apoptosis. To identify candidate genes through which p53 mediates these effects, gene expression was compared between p53 knock-down (p53-KD) and control CHRF cells induced to undergo terminal megakaryocytic differentiation using microarray analysis. Among substantially downregulated p53 targets in p53-KD megakaryocytes were cell cycle regulators CDKN1A (p21) and PLK2, proapoptotic FAS, TNFRSF10B, CASP8, NOTCH1, TP53INP1, TP53I3, DRAM1, ZMAT3 and PHLDA3, DNA-damage-related RRM2B and SESN1, and actin component ACTA2, while antiapoptotic CKS1B, BCL2, GTSE1, and p53 family member TP63 were upregulated in p53-KD cells. Additionally, a number of cell cycle-related, proapoptotic, and cytoskeleton-related genes with known functions in megakaryocytes but not known to carry p53-responsive elements were differentially expressed between p53-KD and control CHRF cells. Our data support a model whereby p53 expression during megakaryopoiesis serves to control polyploidization and the transition from endomitosis to apoptosis by impeding cell cycling and promoting apoptosis. Furthermore, we identify a putative p53 regulon that is proposed to orchestrate these effects.

  8. The Role of Autonomous and Controlled Motivation in Exercise Intentions of Participants in a Mass Cycling Event

    PubMed Central

    Willem, Annick; De Rycke, Jens; Theeboom, Marc

    2017-01-01

    Purpose: This study used self-determination theory to examine the role of participants' autonomous and controlled motivation to exercise and to participate in a challenging mass cycling event and investigated whether the event enhanced intended and actual exercise behavior among the participants. Method: Two hundred and twenty-eight subjects, having participated in the cycling event, completed a questionnaire shortly after the event and again 4 months later. The questionnaire measured self-reported cycling and exercise activity, training in preparation of the event, motivation to participate in the event, motivation to exercise, and future exercise intentions due to the event. Results: Results showed that most participants were very active in cycling and other sports. The expected positive effect of autonomous motivation on exercise intentions and behavior could not be confirmed in our study. Multiple regression analyses revealed that the event had an enhancing effect on exercise intentions shortly after the event among participants that scored higher on controlled motivation to exercise (β = 0.15) and to participate (β = 0.15); also, participants were more satisfied with the event (β = 0.19) and had followed a preparation program before the event (β = 0.15). However, intentions and exercise behavior distinctively dropped 4 months after the event. Conclusions: Events aiming to enhance their participants' exercise behavior need to attract less active participants and need to make additional efforts to prevent relapse in intentions and exercise behavior. PMID:28360871

  9. The Role of Autonomous and Controlled Motivation in Exercise Intentions of Participants in a Mass Cycling Event.

    PubMed

    Willem, Annick; De Rycke, Jens; Theeboom, Marc

    2017-01-01

    Purpose: This study used self-determination theory to examine the role of participants' autonomous and controlled motivation to exercise and to participate in a challenging mass cycling event and investigated whether the event enhanced intended and actual exercise behavior among the participants. Method: Two hundred and twenty-eight subjects, having participated in the cycling event, completed a questionnaire shortly after the event and again 4 months later. The questionnaire measured self-reported cycling and exercise activity, training in preparation of the event, motivation to participate in the event, motivation to exercise, and future exercise intentions due to the event. Results: Results showed that most participants were very active in cycling and other sports. The expected positive effect of autonomous motivation on exercise intentions and behavior could not be confirmed in our study. Multiple regression analyses revealed that the event had an enhancing effect on exercise intentions shortly after the event among participants that scored higher on controlled motivation to exercise (β = 0.15) and to participate (β = 0.15); also, participants were more satisfied with the event (β = 0.19) and had followed a preparation program before the event (β = 0.15). However, intentions and exercise behavior distinctively dropped 4 months after the event. Conclusions: Events aiming to enhance their participants' exercise behavior need to attract less active participants and need to make additional efforts to prevent relapse in intentions and exercise behavior.

  10. New low-dose, extended-cycle pills with levonorgestrel and ethinyl estradiol: an evolutionary step in birth control.

    PubMed

    Nelson, Anita

    2010-08-09

    To review milestones in development of oral contraceptive pills since their introduction in the US 50 years ago in order to better understand how a new formulation with low-dose estrogen in an extended-cycle pattern fits into the evolution of birth control pills. This is a review of trends in the development of various birth controls pills and includes data from phase III clinical trials for this new formulation. The first birth control pill was a very high-dose monophasic formulation with the prodrug estrogen mestranol and a first-generation progestin. Over the decades, the doses of hormones have been markedly reduced, and a new estrogen and several different progestins were developed and used in different dosing patterns. The final element to undergo change was the 7-day pill-free interval. Many of these same changes have been made in the development of extended-cycle pill formulation. The newest extended-cycle oral contraceptive formulation with 84 active pills, each containing 20 μg ethinyl estradiol and 100 μg levonorgestrel, represents an important evolution in birth control that incorporates lower doses of estrogen (to reduce side effects and possibly reduce risk of thrombosis), fewer scheduled bleeding episodes (to meet women's desires for fewer and shorter menses) and the use of low-dose estrogen in place of placebo pills (to reduce the number of days of unscheduled spotting and bleeding). Hopefully, this unique formation will motivate women to be more successful contraceptors.

  11. Ecohydrological and Biophysical Controls on Carbon Cycling in Two Seasonally Snow-covered Forests

    NASA Astrophysics Data System (ADS)

    Chan, A. M.; Brooks, P. D.; Burns, S. P.; Litvak, M. E.; Blanken, P.; Bowling, D. R.

    2014-12-01

    In many seasonally snow-covered forests, the snowpack is the primary water resource. The snowpack also serves as an insulating layer over the soil, warming soil throughout the winter and preserving moisture conditions from the preceding fall. Therefore, the total amount of water in the snowpack as well as the timing and duration of the snow-covered season are likely to have a strong influence on forest productivity through the regulation of the biophysical environment. We investigated how interannual variation in the amount and timing of seasonal snow cover affect winter carbon efflux and growing season carbon uptake at the Niwot Ridge AmeriFlux site (NWT) in Colorado (3050m a.s.l.; 40˚N) and the Valles Caldera Mixed-Conifer AmeriFlux site (VC) in New Mexico (3003m a.s.l.; 36˚N). The tree species composition at NWT is dominated by Abies lasiocarpa, Picea engelmannii, and Pinus contorta. At VC, the dominant tree species are Pseudotsuga menziesii, Abies concolor, Picea pungens, Pinus strobiformis, Pinus flexilis, Pinus ponderosa, and Populus tremuloides. We used net ecosystem exchange (NEE) and climate data from 1999-2012 at NWT and 2007-2012 at VC to divide each year into the growing season, when NEE is negative, and the winter, when NEE is positive. Snow water equivalent (SWE), precipitation, and duration of snow cover data were obtained from USDA/NRCS SNOTEL sites near each forest. At both sites, the start of the growing season was strongly controlled by air temperature, but growing season NEE was not dependent on the length of the growing season. At NWT, total winter carbon efflux was strongly influenced by both the amount and duration of the snowpack, measured as SWE integrated over time. Years with higher integrated SWE had higher winter carbon efflux and also had warmer soil under the snowpack. These patterns were not seen at VC. However, peak SWE amount was positively correlated with growing season NEE at VC, but not at NWT. These results suggest that

  12. Obliquity-Controlled Water Vapor/Trace Gas Feedback in the Martian Greenhouse Cycle

    NASA Astrophysics Data System (ADS)

    Mischna, M. A.; Baker, V. R.; Milliken, R.; Richardson, M. I.; Lee, C.

    2013-12-01

    We have explored possible mechanisms for the generation of warm, wet climates on early Mars as a result of greenhouse warming by both water vapor and periodic volcanic trace gas emissions, using the Mars Weather Research and Forecasting (MarsWRF) general circulation model. The presence of both water vapor (a strong greenhouse gas) and other trace greenhouse gases (such as SO2) in a predominantly CO2 atmosphere may act, under certain conditions, to elevate surface temperatures above the freezing point of liquid water, at least episodically. The levels of warming obtained in our simulations do not reach the values seen in Johnson et al., (2008, JGR, 113, E08005), nor are they widespread for extended periods. Rather, warming above 273 K is found in more localized environments and for geologically brief periods of time. Such periodic episodes are controlled by two factors. First is the obliquity of the planet, which plays a significant role is ';activating' extant surface water ice reservoirs, allowing levels of atmospheric water vapor to rise when obliquity is high, and fall precipitously when the obliquity is low. During these low-obliquity periods, the atmosphere is all but incapable of supporting warm surface temperatures except for brief episodes localized wholly in the tropics; thus, there is a natural regulator in the obliquity cycle for maintaining periodic warming. Second is the presence of a secondary trace gas 'trigger', like volcanically released SO2, in the atmosphere. In the absence of such a trace gas, water vapor alone appears incapable of raising temperatures above the melting point; however, by temporarily raising the baseline global temperatures (in the absence of warming by water vapor) by 10-15 K, as with SO2, the trigger gas keeps atmospheric temperatures sufficiently warm, especially during nighttime, to maintain levels of water vapor in the atmosphere that provide the needed warming. Furthermore, we find that global warming can be achieved more

  13. Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2014-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

  14. Effects of Thermal Cycling on Control and Irradiated EPC 2nd Generation GaN FETs

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2013-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling in order to address their reliability for use in space missions. Results of the experimental work are presented and discussed.

  15. Does local endometrial injury in the nontransfer cycle improve the IVF-ET outcome in the subsequent cycle in patients with previous unsuccessful IVF? A randomized controlled pilot study

    PubMed Central

    Narvekar, Sachin A; Gupta, Neelima; Shetty, Nivedita; Kottur, Anu; Srinivas, MS; Rao, Kamini A

    2010-01-01

    BACKGROUND: Management of repeated implantation failure despite transfer of good-quality embryos still remains a dilemma for ART specialists. Scrapping of endometrium in the nontransfer cycle has been shown to improve the pregnancy rate in the subsequent IVF/ET cycle in recent studies. AIM: The objective of this randomized controlled trial (RCT) was to determine whether endometrial injury caused by Pipelle sampling in the nontransfer cycle could improve the probability of pregnancy in the subsequent IVF cycle in patients who had previous failed IVF outcome. SETTING: Tertiary assisted conception center. DESIGN: Randomized controlled study. MATERIALS AND METHODS: 100 eligible patients with previous failed IVF despite transfer of good-quality embryos were randomly allocated to the intervention group and control groups. In the intervention group, Pipelle endometrial sampling was done twice: One in the follicular phase and again in the luteal phase in the cycle preceding the embryo transfer cycle. OUTCOME MEASURE: The primary outcome measure was live birth rate. The secondary outcome measures were implantation and clinical pregnancy rates. RESULTS: The live birth rate was significantly higher in the intervention group compared to control group (22.4% and 9.8% P = 0.04). The clinical pregnancy rate in the intervention group was 32.7%, while that in the control group was 13.7%, which was also statistically significant (P = 0.01). The implantation rate was significantly higher in the intervention group as compared to controls (13.07% vs 7.1% P = 0.04). CONCLUSIONS: Endometrial injury in nontransfer cycle improves the live birth rate, clinical pregnancy and implantation rates in the subsequent IVF-ET cycle in patients with previous unsuccessful IVF cycles. PMID:20607003

  16. Does local endometrial injury in the nontransfer cycle improve the IVF-ET outcome in the subsequent cycle in patients with previous unsuccessful IVF? A randomized controlled pilot study.

    PubMed

    Narvekar, Sachin A; Gupta, Neelima; Shetty, Nivedita; Kottur, Anu; Srinivas, Ms; Rao, Kamini A

    2010-01-01

    Management of repeated implantation failure despite transfer of good-quality embryos still remains a dilemma for ART specialists. Scrapping of endometrium in the nontransfer cycle has been shown to improve the pregnancy rate in the subsequent IVF/ET cycle in recent studies. The objective of this randomized controlled trial (RCT) was to determine whether endometrial injury caused by Pipelle sampling in the nontransfer cycle could improve the probability of pregnancy in the subsequent IVF cycle in patients who had previous failed IVF outcome. Tertiary assisted conception center. Randomized controlled study. 100 eligible patients with previous failed IVF despite transfer of good-quality embryos were randomly allocated to the intervention group and control groups. In the intervention group, Pipelle endometrial sampling was done twice: One in the follicular phase and again in the luteal phase in the cycle preceding the embryo transfer cycle. The primary outcome measure was live birth rate. The secondary outcome measures were implantation and clinical pregnancy rates. The live birth rate was significantly higher in the intervention group compared to control group (22.4% and 9.8% P = 0.04). The clinical pregnancy rate in the intervention group was 32.7%, while that in the control group was 13.7%, which was also statistically significant (P = 0.01). The implantation rate was significantly higher in the intervention group as compared to controls (13.07% vs 7.1% P = 0.04). Endometrial injury in nontransfer cycle improves the live birth rate, clinical pregnancy and implantation rates in the subsequent IVF-ET cycle in patients with previous unsuccessful IVF cycles.

  17. Vegetation, Hydrology and Biogeochemical Cycling: An Integrated View of Controls, Linkages and Feedbacks

    NASA Astrophysics Data System (ADS)

    Reynolds, J. F.

    2003-12-01

    Many current environmental challenges (e.g., diminished water quality and supply, desertified ecosystems, climate change impacts) require an interdisciplinary understanding of the coupled behavior of vegetation, hydrology, and biogeochemical cycling. Perhaps nowhere is such interdisciplinary insight more important than in the water-limited arid and semi-arid regions of the Earth. Vegetation plays a key role in hydrological processes in these systems, affecting the evaporation, transpiration, runoff, and recharge components of the water balance. Similarly, hydrological processes are a major determinant of many ecosystem processes, including seed germination, primary productivity, the distribution of vegetation, and biogeochemical cycling of carbon, nitrogen, and other nutrients. Using examples from the Mojave, Sonoran and Chihuahuan deserts of North America, this lecture will examine the interrelated roles of vegetation, hydrological cycles and biogeochemical cycles, ranging from patch to watershed scales. Key components, nonlinearities and linkages will be identified, including critical gaps in our understanding and new approaches and methods needed to advance our current ability to characterize and model complex environmental systems. These issues will be addressed in the context of both theoretical and field-based research.

  18. Two-stroke-cycle engines with unsymmetrical control diagram : supercharged engines

    NASA Technical Reports Server (NTRS)

    Zeman, J

    1939-01-01

    As no investigation of supercharging in 2-stroke-cycle engines has been published up to the present, this article is an attempt in that direction, with a view to establishing the mathematical principles and the constructive rules for the design of such engines.

  19. Vegetation controls on carbon and nitrogen cycling and retention: contrasts in spruce and hardwood watershed budgets

    Treesearch

    Charlene N. Kelly; Stephen H. Schoenholtz; Mary Beth. Adams

    2010-01-01

    Anthropogenic sources of nitrogen (N) have altered the global N cycle to such an extent as to nearly double the rate of N that enters many terrestrial ecosystems. However, predicting the fate of N inputs continues to present challenges, as a multitude of environmental factors play major roles in determining N pathways. This research investigates the role of specific...

  20. A Spatial Control for Correct Timing of Gene Expression during the Escherichia coli Cell Cycle

    PubMed Central

    Yao, Yuan; Fan, Lifei; Shi, Yixin; Odsbu, Ingvild; Morigen

    2016-01-01

    Temporal transcriptions of genes are achieved by different mechanisms such as dynamic interaction of activator and repressor proteins with promoters, and accumulation and/or degradation of key regulators as a function of cell cycle. We find that the TorR protein localizes to the old poles of the Escherichia coli cells, forming a functional focus. The TorR focus co-localizes with the nucleoid in a cell-cycle-dependent manner, and consequently regulates transcription of a number of genes. Formation of one TorR focus at the old poles of cells requires interaction with the MreB and DnaK proteins, and ATP, suggesting that TorR delivery requires cytoskeleton organization and ATP. Further, absence of the protein–protein interactions and ATP leads to loss in function of TorR as a transcription factor. We propose a mechanism for timing of cell-cycle-dependent gene transcription, where a transcription factor interacts with its target genes during a specific period of the cell cycle by limiting its own spatial distribution. PMID:28025549

  1. Precision control of soil N cycling via soil functional zone management

    USDA-ARS?s Scientific Manuscript database

    Managing the soil nitrogen (N) cycle is a major component of agricultural sustainability. Soil functional zone management (SFZM), a novel framework of agroecosystem management, may improve soil N management compared with conventional and no-tillage approaches by focusing on the timing and location (...

  2. The Good, the Bad and the Ugly - Interacting Physical, Biogeochemical and Biolological Controls of Nutrient Cycling at Ecohydrological Interfaces

    NASA Astrophysics Data System (ADS)

    Krause, S.; Baranov, V. A.; Lewandowski, J.; Blaen, P. J.; Romeijn, P.

    2016-12-01

    The interfaces between streams, lakes and their bed sediments have for a long time been in the research focus of ecohydrologists, aquatic ecologists and biogeochemists. While over the past decades, critical understanding has been gained of the spatial patterns and temporal dynamics in nutrient cycling at sediment-freshwater interfaces, important question remain as to the actual drivers (physical, biogeochemical and biological) of the often observed hot spots and hot moments of nutrient cycling at these highly reactive systems. This study reports on a combination of laboratory manipulation, artificial stream and field experiments from reach to river network scales to investigate the interplay of physical, biogeochemical and biological drivers of interface nutrient cycling under the impact of and resilience to global environmental change. Our results indicate that biogeochemical hotspots at sediment-freshwater interfaces were controlled not only by reactant mixing ratios and residence time distributions, but strongly affected by patterns in streambed physical properties and bioavailability of organic carbon. Lab incubation experiments revealed that geology, and in particular organic matter content strongly controlled the magnitude of enhanced streambed greenhouse gas production caused by increasing water temperatures. While these findings help to improve our understanding of physical and biogeochemical controls on nutrient cycling, we only start to understand to what degree biological factors can enhance these processes even further. We found that for instance chironomid or brittle star facilitated bioturbation in has the potential to substantially enhance freshwater or marine sediment pore-water flow and respiration. We revealed that ignorance of these important biologically controls on physical exchange fluxes can lead to critical underestimation of whole system respiration and its increase under global environmental change.

  3. Feedback control of variability in the cycle period of a central pattern generator.

    PubMed

    Hooper, Ryan M; Tikidji-Hamburyan, Ruben A; Canavier, Carmen C; Prinz, Astrid A

    2015-11-01

    We address how feedback to a bursting biological pacemaker with intrinsic variability in cycle length can affect that variability. Specifically, we examine a hybrid circuit constructed of an isolated crab anterior burster (AB)/pyloric dilator (PD) pyloric pacemaker receiving virtual feedback via dynamic clamp. This virtual feedback generates artificial synaptic input to PD with timing determined by adjustable phase response dynamics that mimic average burst intervals generated by the lateral pyloric neuron (LP) in the intact pyloric network. Using this system, we measure network period variability dependence on the feedback element's phase response dynamics and find that a constant response interval confers minimum variability. We further find that these optimal dynamics are characteristic of the biological pyloric network. Building upon our previous theoretical work mapping the firing intervals in one cycle onto the firing intervals in the next cycle, we create a theoretical map of the distribution of all firing intervals in one cycle to the distribution of firing intervals in the next cycle. We then obtain an integral equation for a stationary self-consistent distribution of the network periods of the hybrid circuit, which can be solved numerically given the uncoupled pacemaker's distribution of intrinsic periods, the nature of the network's feedback, and the phase resetting characteristics of the pacemaker. The stationary distributions obtained in this manner are strongly predictive of the experimentally observed distributions of hybrid network period. This theoretical framework can provide insight into optimal feedback schemes for minimizing variability to increase reliability or maximizing variability to increase flexibility in central pattern generators driven by pacemakers with feedback.

  4. Feedback control of variability in the cycle period of a central pattern generator

    PubMed Central

    Tikidji-Hamburyan, Ruben A.; Canavier, Carmen C.; Prinz, Astrid A.

    2015-01-01

    We address how feedback to a bursting biological pacemaker with intrinsic variability in cycle length can affect that variability. Specifically, we examine a hybrid circuit constructed of an isolated crab anterior burster (AB)/pyloric dilator (PD) pyloric pacemaker receiving virtual feedback via dynamic clamp. This virtual feedback generates artificial synaptic input to PD with timing determined by adjustable phase response dynamics that mimic average burst intervals generated by the lateral pyloric neuron (LP) in the intact pyloric network. Using this system, we measure network period variability dependence on the feedback element's phase response dynamics and find that a constant response interval confers minimum variability. We further find that these optimal dynamics are characteristic of the biological pyloric network. Building upon our previous theoretical work mapping the firing intervals in one cycle onto the firing intervals in the next cycle, we create a theoretical map of the distribution of all firing intervals in one cycle to the distribution of firing intervals in the next cycle. We then obtain an integral equation for a stationary self-consistent distribution of the network periods of the hybrid circuit, which can be solved numerically given the uncoupled pacemaker's distribution of intrinsic periods, the nature of the network's feedback, and the phase resetting characteristics of the pacemaker. The stationary distributions obtained in this manner are strongly predictive of the experimentally observed distributions of hybrid network period. This theoretical framework can provide insight into optimal feedback schemes for minimizing variability to increase reliability or maximizing variability to increase flexibility in central pattern generators driven by pacemakers with feedback. PMID:26334008

  5. Transcriptional control of fungal cell cycle and cellular events by Fkh2, a forkhead transcription factor in an insect pathogen

    PubMed Central

    Wang, Juan-Juan; Qiu, Lei; Cai, Qing; Ying, Sheng-Hua; Feng, Ming-Guang

    2015-01-01

    Transcriptional control of the cell cycle by forkhead (Fkh) transcription factors is likely associated with fungal adaptation to host and environment. Here we show that Fkh2, an ortholog of yeast Fkh1/2, orchestrates cell cycle and many cellular events of Beauveria bassiana, a filamentous fungal insect pathogen. Deletion of Fkh2 in B. bassiana resulted in dramatic down-regulation of the cyclin-B gene cluster and hence altered cell cycle (longer G2/M and S, but shorter G0/G1, phases) in unicellular blastospores. Consequently, ΔFkh2 produced twice as many, but smaller, blastospores than wild-type under submerged conditions, and formed denser septa and shorter/broader cells in aberrantly branched hyphae. In these hyphae, clustered genes required for septation and conidiation were remarkedly up-regulated, followed by higher yield and slower germination of aerial conidia. Moreover, ΔFkh2 displayed attenuated virulence and decreased tolerance to chemical and environmental stresses, accompanied with altered transcripts and activities of phenotype-influencing proteins or enzymes. All the changes in ΔFkh2 were restored by Fkh2 complementation. All together, Fkh2-dependent transcriptional control is vital for the adaptation of B. bassiana to diverse habitats of host insects and hence contributes to its biological control potential against arthropod pests. PMID:25955538

  6. Modified natural cycle versus controlled ovarian hyperstimulation IVF: a cost-effectiveness evaluation of three simulated treatment scenarios.

    PubMed

    Groen, Henk; Tonch, Nino; Simons, Arnold H M; van der Veen, Fulco; Hoek, Annemieke; Land, Jolande A

    2013-12-01

    Can modified natural cycle IVF or ICSI (MNC) be a cost-effective alternative for controlled ovarian hyperstimulation IVF or ICSI (COH)? The comparison of simulated scenarios indicates that a strategy of three to six cycles of MNC with minimized medication is a cost-effective alternative for one cycle of COH with strict application of single embryo transfer (SET). MNC is cheaper per cycle than COH but also less effective in terms of live birth rate (LBR). However, strict application of SET in COH cycles reduces effectiveness and up to three MNC cycles can be performed at the same costs as one COH cycle. The cost-effectiveness of MNC versus COH was evaluated in three simulated treatment scenarios: three cycles of MNC versus one cycle of COH with SET or double embryo transfer (DET) and subsequent transfer of cryopreserved embryos (Scenario 1); six cycles of MNC versus one cycle of COH with strictly SET and subsequent transfer of cryopreserved embryos (Scenario 2); six cycles of MNC with minimized medication (hCG ovulation trigger only) versus one cycle of COH with SET or DET and subsequent transfer of cryopreserved embryos (Scenario 3). We used baseline data obtained from two retrospective cohorts of consecutive patients (2005-2008) undergoing MNC in the University Medical Center Groningen (n = 499, maximum six cycles per patient) or their first COH cycle with subsequent transfer of cryopreserved embryos in the Academic Medical Center Amsterdam (n = 392). Data from 1994 MNC cycles (958 MNC-IVF and 1036 MNC-ICSI) and 392 fresh COH cycles (one per patient, 196 COH-IVF and 196 COH-ICSI) with subsequent transfer of cryopreserved embryos (n = 72 and n = 94 in MNC and COH cycles, respectively) in ovulatory, subfertile women <36 years of age served as baseline for the three simulated scenarios. To compare the scenarios, the incremental cost-effectiveness ratio (ICER) was calculated, defined as the ratio of the difference in IVF costs up to 6 weeks postpartum to the

  7. Interhemispheric controls on deep ocean circulation and carbon chemistry during the last two glacial cycles

    NASA Astrophysics Data System (ADS)

    Wilson, David J.; Piotrowski, Alexander M.; Galy, Albert; Banakar, Virupaxa K.

    2015-06-01

    Changes in ocean circulation structure, together with biological cycling, have been proposed for trapping carbon in the deep ocean during glacial periods of the Late Pleistocene, but uncertainty remains in the nature and timing of deep ocean circulation changes through glacial cycles. In this study, we use neodymium (Nd) and carbon isotopes from a deep Indian Ocean sediment core to reconstruct water mass mixing and carbon cycling in Circumpolar Deep Water over the past 250 thousand years, a period encompassing two full glacial cycles and including a range of orbital forcing. Building on recent studies, we use reductive sediment leaching supported by measurements on isolated phases (foraminifera and fish teeth) in order to obtain a robust seawater Nd isotope reconstruction. Neodymium isotopes record a changing North Atlantic Deep Water (NADW) component in the deep Indian Ocean that bears a striking resemblance to Northern Hemisphere climate records. In particular, we identify both an approximately in-phase link to Northern Hemisphere summer insolation in the precession band and a longer-term reduction of NADW contributions over the course of glacial cycles. The orbital timescale changes may record the influence of insolation forcing, for example via NADW temperature and/or Antarctic sea ice extent, on deep stratification and mixing in the Southern Ocean, leading to isolation of the global deep oceans from an NADW source during times of low Northern Hemisphere summer insolation. That evidence could support an active role for changing deep ocean circulation in carbon storage during glacial inceptions. However, mid-depth water mass mixing and deep ocean carbon storage were largely decoupled within glacial periods, and a return to an interglacial-like circulation state during marine isotope stage (MIS) 6.5 was accompanied by only minor changes in atmospheric CO2. Although a gradual reduction of NADW export through glacial periods may have produced slow climate feedbacks

  8. Versatility of global transcriptional regulators in alpha-Proteobacteria: from essential cell cycle control to ancillary functions.

    PubMed

    Panis, Gaël; Murray, Sean R; Viollier, Patrick H

    2015-01-01

    Recent data indicate that cell cycle transcription in many alpha-Proteobacteria is executed by at least three conserved functional modules in which pairs of antagonistic regulators act jointly, rather than in isolation, to control transcription in S-, G2- or G1-phase. Inactivation of module components often results in pleiotropic defects, ranging from cell death and impaired cell division to fairly benign deficiencies in motility. Expression of module components can follow systemic (cell cycle) or external (nutritional/cell density) cues and may be implemented by auto-regulation, ancillary regulators or other (unknown) mechanisms. Here, we highlight the recent progress in understanding the molecular events and the genetic relationships of the module components in environmental, pathogenic and/or symbiotic alpha-proteobacterial genera. Additionally, we take advantage of the recent genome-wide transcriptional analyses performed in the model alpha-Proteobacterium Caulobacter crescentus to illustrate the complexity of the interactions of the global regulators at selected cell cycle-regulated promoters and we detail the consequences of (mis-)expression when the regulators are absent. This review thus provides the first detailed mechanistic framework for understanding orthologous operational principles acting on cell cycle-regulated promoters in other alpha-Proteobacteria. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. Coherent Electronic Wave Packet Motion in C60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

    NASA Astrophysics Data System (ADS)

    Li, H.; Mignolet, B.; Wachter, G.; Skruszewicz, S.; Zherebtsov, S.; Süßmann, F.; Kessel, A.; Trushin, S. A.; Kling, Nora G.; Kübel, M.; Ahn, B.; Kim, D.; Ben-Itzhak, I.; Cocke, C. L.; Fennel, T.; Tiggesbäumker, J.; Meiwes-Broer, K.-H.; Lemell, C.; Burgdörfer, J.; Levine, R. D.; Remacle, F.; Kling, M. F.

    2015-03-01

    Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.

  10. Quantum path control in harmonic generation by temporal shaping of few-optical-cycle pulses in ionizing media

    SciTech Connect

    Calegari, F.; Lucchini, M.; Ferrari, F.; Vozzi, C.; Stagira, S.; Sansone, G.; Nisoli, M.; Kim, K. S.

    2011-10-15

    Temporal reshaping of the electric field of few-optical-cycle pulses in a low-density ionizing gas has been used to achieve control of the electron trajectories in the process of high-order harmonic generation. As a result of such a quantum path control mechanism, isolated or multiple attosecond pulses have been produced, depending on the carrier-envelope phase of the driving field. In particular, complete spectral tunability of the harmonic peaks over the whole spectral range has been demonstrated. Experimental results have been interpreted using a nonadiabatic three-dimensional propagation model and a nonadiabatic stationary phase model.

  11. MicroRNAs (miRNAs) in the control of HF development and cycling: the next frontiers in hair research.

    PubMed

    Andl, Thomas; Botchkareva, Natalia V

    2015-11-01

    Hair follicle development and its postnatal regeneration are characterized by dramatic changes in its microanatomy and cellular activity, which are controlled by multiple signalling pathways, transcription factors and epigenetic regulators, including microRNAs (miRNAs). miRNAs and their targets form remarkably diverse regulatory networks, playing a key role in the execution of gene expression programmes in the different cell lineages of the hair follicle. This review summarizes the roles of miRNAs in the control of hair follicle development, cycling and hair pigmentation, emphasizes the remaining problems/unanswered questions, and provides future directions in this rapidly growing and exciting area of research.

  12. Vascular plant controls on carbon cycling and greenhouse gas fluxes in wetlands

    NASA Astrophysics Data System (ADS)

    Ström, L.; Christensen, T.

    2003-04-01

    carbon cycling of ecosystems is highly species-specific. In accordance with the field experiment in Greenland we found higher formation rates of acetate in the root vicinity of the Eriophorum species. The data from this experiment, however, also points to the importance of plants as transporters of oxygen to anoxic layers. When 14CH_3-COO^- (which theoretically would result exclusively in 14CH_4 emission if no oxidation to 14CO_2 takes place) was added to monoliths containing these three species E. vaginatum and J. effucum was shown to almost completely oxidize their root vicinity, whereas, C. rostrata did not. At the end of the experiment E. vaginatum and J. effucum had emitted the added 14C to >90% as 14CO_2 and C. rostrata to 70% as 14CH_4. In conclusion, our results point toward a direct and very important linkage between plant species diversity and the functioning of wetland ecosystems and indicate that changes in species composition may alter important processes relating to controls on and interactions between greenhouse gas fluxes with significant implications for feedback mechanisms in a changing climate as result.

  13. Biotic controls over the carbon cycle in dryland ecosystems under climate change

    NASA Astrophysics Data System (ADS)

    Grünzweig, J. M.; Sternberg, M.

    2012-04-01

    The majority of land types in the vast drylands of the globe are composed of spatially heterogeneous ecosystems, such as shrublands. These systems are ideally suited for studying biotic effects on the carbon cycle, considering that they are composed of a matrix of distinct vegetated microsites, such as shrubs and herbaceous patches among shrubs. Climate change in many drylands will result in drier conditions as a consequence of lower rain amounts and higher temperatures. Soil respiration (SR) is the greatest fraction of ecosystem respiration in shrublands, and, thus, largely controls the carbon balance in such systems. Because SR under shrubs is higher than SR in herbaceous patches, the decline in shrub cover with increasing drought under climate change could potentially be the main determining factor of the decrease in SR at the ecosystem scale. In an eastern Mediterranean region, shrub cover decreased linearly along a steep aridity gradient which served as a long-term climate-change proxy. However, biological activity as measured by SR and soil CO2 production decreased logarithmically and at a greater rate along the gradient, and this decrease occurred at the same rate both under and between shrubs. Therefore, the decrease in ecosystem-level SR following rainfall reduction is mainly driven by the decline in biological activity and less by the changed relative distribution of vegetation types. Plant biomass and cover represent essentially the activity of ephemerals in herbaceous patches. The decrease in organic carbon storage with increased aridity correlated with an exponential reduction in biomass production and a less pronounced reduction in the decay of organic matter. It appears that under drier conditions, less organic carbon is produced and this carbon is decomposed at a relatively high rate. Plant species composition in herbaceous patches changed along the gradient, which was associated with alterations in plant functional traits. Leaf nitrogen content

  14. Water-table height and microtopography control biogeochemical cycling in an Arctic coastal tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Lipson, D. A.; Zona, D.; Raab, T. K.; Bozzolo, F.; Mauritz, M.; Oechel, W. C.

    2012-01-01

    Drained thaw lake basins (DTLB's) are the dominant land form of the Arctic Coastal Plain in northern Alaska. The presence of continuous permafrost prevents drainage and so water tables generally remain close to the soil surface, creating saturated, suboxic soil conditions. However, ice wedge polygons produce microtopographic variation in these landscapes, with raised areas such as polygon rims creating more oxic microenvironments. The peat soils in this ecosystem store large amounts of organic carbon which is vulnerable to loss as arctic regions continue to rapidly warm, and so there is great motivation to understand the controls over microbial activity in these complex landscapes. Here we report the effects of experimental flooding, along with seasonal and spatial variation in soil chemistry and microbial activity in a DTLB. The flooding treatment generally mirrored the effects of natural landscape variation in water-table height due to microtopography. The flooded portion of the basin had lower dissolved oxygen, lower oxidation-reduction potential (ORP) and higher pH, as did lower elevation areas throughout the entire basin. Similarly, soil pore water concentrations of organic carbon and aromatic compounds were higher in flooded and low elevation areas. Dissolved ferric iron (Fe(III)) concentrations were higher in low elevation areas and responded to the flooding treatment in low areas, only. The high concentrations of soluble Fe(III) in soil pore water were explained by the presence of siderophores, which were much more concentrated in low elevation areas. All the aforementioned variables were correlated, showing that Fe(III) is solubilized in response to anoxic conditions. Dissolved carbon dioxide (CO2) and methane (CH4) concentrations were higher in low elevation areas, but showed only subtle and/or seasonally dependent effects of flooding. In anaerobic laboratory incubations, more CH4 was produced by soils from low and flooded areas, whereas anaerobic CO2

  15. The influence of abiotic controls and management intensity on phosphorus cycling in established grassland and forest ecosystems

    NASA Astrophysics Data System (ADS)

    Alt, F.; Oelmann, Y.; Wilcke, W.

    2011-12-01

    It is commonly assumed that the bioavailability and cycling of phosphorus (P) is mainly controlled by abiotic soil properties including soil pH and the concentrations and reactivities of clay minerals, CaCO3 and Al/Fe oxides In managed ecosystems, kind, timing and duration of P additions and type and amount of harvested biomass are the major input and output fluxes. Our objective was to disentangle the effects of abiotic controls, and type and intensity of management on the P cycle in soils of temperate grasslands and forests of different management intensity in three regions across Germany in the frame of the Biodiversity Exploratories project. The pH value was the most important variable explaining P concentrations and partitioning in soil and changes in pH are the main mechanism how land-use is affecting the P cycle. However, after the influence of pH was accounted for in a sequential statistical approach, land-use intensity, classified according to the extent of annual biomass removal, explained a significant (P < 0.05) part of the variance in the contributions of several P fractions to total P (TP) among all studied regions and land-use types. In grassland soils of highly diverse systems (up to 57 plant species) in one of the study regions, the Schwäbische Alb, a mid-range mountain area on limestone where soils showed a limited variation in pH in the carbonate buffer range, pedogenic Fe oxide concentrations, fertilizer-P application rates, and TP concentrations in soil explained more than half of the variation in bioavailable inorganic (Pi) concentrations extracted with NaHCO3 in soil. Our results demonstrate that mainly soil pH and mineralogical composition, and intensity of management of the managed ecosystems are significant controls of the P cycle determining the size of bioavailable P pool in soil.

  16. Atoms in half-cycle pulses: a laboratory for wavefunction tailoring, coherent control, and quantum chaos

    NASA Astrophysics Data System (ADS)

    Burgdoerfer, Joachim

    2004-05-01

    The ultimate limit of a short pulse is a half-cycle pulse (HCP) subtending only a fraction of an ``optical cycle''. Single pulses as well as trains of HCP's are currently experimentally accessible in the GHz and THz regimes. In Rydberg atoms the duration of such HCP's is short compared to the electronic orbital period representing an impulsive ``kick''. HCP sequences allow to shape and manipulate the time-dependent wavefunction in an (almost) arbitrary fashion. We illustrate the potential of this tool with a few examples: quantum localization in classical chaos, tayloring of wavepackets with low entropy, and probing the coordinate and momentum of a bound electron. Generation of HCP's on an attosecond scale will be discussed. Work supported by FWF, NSF, and DCS, OBES, U.S. DoE, managed by UT-Batelle LLC under contract #DE-AC05-00OR22725.

  17. Tidal cycle control of biogeochemical and ecological properties of a macrotidal ecosystem

    NASA Astrophysics Data System (ADS)

    Cadier, Mathilde; Gorgues, Thomas; LHelguen, Stéphane; Sourisseau, Marc; Memery, Laurent

    2017-08-01

    In some regions, tidal energy can be a key factor in the generation of variability in physical and biogeochemical properties throughout the water column. We use a numerical model resolving tidal cycles and simulating diversity in phytoplankton to assess the impact of tidal mixing on vertical stability and phytoplankton community (total biomass and diversity) in a macrotidal sea (Iroise Sea, France). Two different time scales have been considered: semidiurnal and spring/neap tidal cycles. Our results show that the latter is the one primarily influencing the phytoplankton growth conditions by modifying the vertical stratification. During spring tide, the growth is rather light limited, whereas neap tide conditions lead to vertical stabilization and better light conditions in the shallow surface layer. The transition from high to low tidal mixing conditions is thus associated with a total phytoplankton biomass increase (caused by the rapid development of fast-growing diatoms) and reduced phytoplankton diversity.

  18. Coherent control of atomic excitation using off-resonant strong few-cycle pulses

    SciTech Connect

    Jha, Pankaj K.; Eleuch, Hichem; Rostovtsev, Yuri V.

    2010-10-15

    We study the dynamics of a two-level system driven by an off-resonance few-cycle pulse which has a phase jump {phi} at t=t{sub 0}, in contrast to many-cycle pulses, under the nonrotating-wave approximation (NRWA). We give a closed form analytical solution for the evolution of the probability amplitude |C{sub a}(t)| for the upper level. Using the appropriate pulse parameters like the phase jump {phi}, jump time t{sub 0}, pulse width {tau}, frequency {nu}, and Rabi frequency {Omega}{sub 0} the population transfer after the pulse is gone can be optimized and, for the pulse considered here, an enhancement factor of 10{sup 6}-10{sup 8} was obtained.

  19. Effects of seawater acidification on cell cycle control mechanisms in Strongylocentrotus purpuratus embryos.

    PubMed

    Place, Sean P; Smith, Bryan W

    2012-01-01

    Previous studies have shown fertilization and development of marine species can be significantly inhibited when the pH of sea water is artificially lowered. Little mechanistic understanding of these effects exists to date, but previous work has linked developmental inhibition to reduced cleavage rates in embryos. To explore this further, we tested whether common cell cycle checkpoints were involved using three cellular biomarkers of cell cycle progression: (1) the onset of DNA synthesis, (2) production of a mitotic regulator, cyclin B, and (3) formation of the mitotic spindle. We grew embryos of the purple sea urchin, Strongylocentrotus purpuratus, in seawater artifically buffered to a pH of ∼7.0, 7.5, and 8.0 by CO(2) infusion. Our results suggest the reduced rates of mitotic cleavage are likely unrelated to common cell cycle checkpoints. We found no significant differences in the three biomarkers assessed between pH treatments, indicating the embryos progress through the G(1)/S, G(2)/M and metaphase/anaphase transitions at relatively similar rates. These data suggest low pH environments may not impact developmental programs directly, but may act through secondary mechanisms such as cellular energetics.

  20. Control of DNA polymerase λ stability by phosphorylation and ubiquitination during the cell cycle

    PubMed Central

    Wimmer, Ursula; Ferrari, Elena; Hunziker, Peter; Hübscher, Ulrich

    2008-01-01

    DNA polymerase (Pol) λ is a DNA repair enzyme involved in base excision repair, non-homologous end joining and translesion synthesis. Recently, we identified Pol λ as an interaction partner of cyclin-dependent kinase 2 (CDK2) that is central to the cell cycle G1/S transition and S-phase progression. This interaction leads to in vitro phosphorylation of Pol λ, and its in vivo phosphorylation pattern during cell cycle progression mimics the modulation of CDK2/cyclin A. Here, we identify several phosphorylation sites of Pol λ. Experiments with phosphorylation-defective mutants suggest that phosphorylation of Thr 553 is important for maintaining Pol λ stability, as it is targeted to the proteasomal degradation pathway through ubiquitination unless this residue is phosphorylated. In particular, Pol λ is stabilized during cell cycle progression in the late S and G2 phases. This most likely allows Pol λ to correctly conduct repair of damaged DNA during and after S phase. PMID:18688254

  1. Control of the estrous cycle in guinea-pig (Cavia porcellus).

    PubMed

    Grégoire, A; Allard, A; Huamán, E; León, S; Silva, R M; Buff, S; Berard, M; Joly, T

    2012-09-01

    The aim of this work was to look for a simple method to obtain synchronized ovulation in guinea pigs under farming conditions while respecting animal welfare. The luteolytic activity of three different prostaglandins F2alpha (PGF2α) analogs (D-cloprostenol, D,L-cloprostenol and luprostiol) and a daily treatment with oral progestagen (altrenogest) was tested successively at different stages of the estrous cycle on the same group of females during a period of 8 mo. The estrous cycle length was not modified by the administration of PGF2α analogs, whatever the stage of the estrous cycle when the treatment was initiated. Our results led us to reject the use of PGF2α analog to induce practical synchronization of the estrus in this species. In females (n = 29), given 15 days with altrenogest (0.1 mL po once a day), ovulation occurred 4.43 ± 0.13 days after the end of the treatment. Altrenogest treatment was followed by mating. No negative impacts of the treatment on the pregnancy rates, delivery rates and litter sizes were observed. This standard method of guinea-pig estrus synchronization is less stressful for the animals compared to techniques using progesterone tubing.

  2. Spindle-E cycling between nuage and cytoplasm is controlled by Qin and PIWI proteins

    PubMed Central

    Andress, Arlise; Bei, Yanxia; Fonslow, Bryan R.; Giri, Ritika; Wu, Yilong; Yates, John R.

    2016-01-01

    Transposable elements (TEs) are silenced in germ cells by a mechanism in which PIWI proteins generate and use PIWI-interacting ribonucleic acid (piRNA) to repress expression of TE genes. piRNA biogenesis occurs by an amplification cycle in microscopic organelles called nuage granules, which are localized to the outer face of the nuclear envelope. One cofactor required for amplification is the helicase Spindle-E (Spn-E). We found that the Spn-E protein physically associates with the Tudor domain protein Qin and the PIWI proteins Aubergine (Aub) and Argonaute3 (Ago3). Spn-E and Qin proteins are mutually dependent for their exit from nuage granules, whereas Spn-E and both Aub and Ago3 are mutually dependent for their entry or retention in nuage. The result is a dynamic cycling of Spn-E and its associated factors in and out of nuage granules. This implies that nuage granules can be considered to be hubs for active, mobile, and transient complexes. We suggest that this is in some way coupled with the execution of the piRNA amplification cycle. PMID:27091448

  3. Temperature and rainfall interact to control carbon cycling in tropical forests.

    PubMed

    Taylor, Philip G; Cleveland, Cory C; Wieder, William R; Sullivan, Benjamin W; Doughty, Christopher E; Dobrowski, Solomon Z; Townsend, Alan R

    2017-06-01

    Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short-term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer-term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate - C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm tropical forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate - C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth. © 2017 John Wiley & Sons Ltd/CNRS.

  4. Rethinking the clockwork: redox cycles and non-transcriptional control of circadian rhythms.

    PubMed

    Wu, Lisa; Reddy, Akhilesh B

    2014-02-01

    Circadian rhythms are a hallmark of living organisms, observable in all walks of life from primitive bacteria to highly complex humans. They are believed to have evolved to co-ordinate the timing of biological and behavioural processes to the changing environmental needs brought on by the progression of day and night through the 24-h cycle. Most of the modern study of circadian rhythms has centred on so-called TTFLs (transcription-translation feedback loops), wherein a core group of 'clock' genes, capable of negatively regulating themselves, produce oscillations with a period of approximately 24 h. Recently, however, the prevalence of the TTFL paradigm has been challenged by a series of findings wherein circadian rhythms, in the form of redox reactions, persist in the absence of transcriptional cycles. We have found that circadian cycles of oxidation and reduction are conserved across all domains of life, strongly suggesting that non-TTFL mechanisms work in parallel with the canonical genetic processes of timekeeping to generate the cyclical cellular and behavioural phenotypes that we commonly recognize as circadian rhythms.

  5. Fuel cycle facility control system for the Integral Fast Reactor Program

    SciTech Connect

    Benedict, R.W.; Tate, D.A.

    1993-09-01

    As part of the Integral Fast Reactor (IFR) Fuel Demonstration, a new distributed control system designed, implemented and installed. The Fuel processes are a combination of chemical and machining processes operated remotely. To meet this special requirement, the new control system provides complete sequential logic control motion and positioning control and continuous PID loop control. Also, a centralized computer system provides near-real time nuclear material tracking, product quality control data archiving and a centralized reporting function. The control system was configured to use programmable logic controllers, small logic controllers, personal computers with touch screens, engineering work stations and interconnecting networks. By following a structured software development method the operator interface was standardized. The system has been installed and is presently being tested for operations.

  6. Sub-cycle directional control of the dissociative ionization of H2 in tailored femtosecond laser fields

    NASA Astrophysics Data System (ADS)

    Li, H.; Gong, X.; Lin, K.; de Vivie-Riedle, R.; Tong, X. M.; Wu, J.; Kling, M. F.

    2017-09-01

    Being the simplest molecule on the planet, H2, as well as its isotopes, have been the prototype systems for strong-field molecular physics for decades. Photoionization and dissociation of H2 have been extensively investigated. After single ionization, the electron left in the molecular ion and its microscopic localization around the two dissociating nuclei can be effectively manipulated using intense femtosecond laser fields with broken symmetry. In this paper, we review the recent progress made on the sub-cycle directional control of the dissociative ionization of hydrogen molecules by tailoring the waveform of femtosecond laser fields, including few-cycle pulses and 2-color fields polarized along the same direction (one-dimension) or different directions (two-dimension).

  7. Position in cell cycle controls the sensitivity of colon cancer cells to nitric oxide-dependent programmed cell death.

    PubMed

    Jarry, Anne; Charrier, Laetitia; Bou-Hanna, Chantal; Devilder, Marie-Claire; Crussaire, Véronique; Denis, Marc G; Vallette, Geneviève; Laboisse, Christian L

    2004-06-15

    Mounting evidence suggests that the position in the cell cycle of cells exposed to an oxidative stress could determine their survival or apoptotic cell death. This study aimed at determining whether nitric oxide (NO)-induced cell death in colon cancer cells might depend on their position in the cell cycle, based on a clone of the cancer cell line HT29 exposed to an NO donor, in combination with the manipulation of the cell entry into the cell cycle. We show that PAPA NONOate (pNO), from 10(-4) m to 10(-3) m, exerted early and reversible cytostatic effects through ribonucleotide reductase inhibition, followed by late resumption of cell growth at 5 x 10(-4) m pNO. In contrast, 10(-3) m pNO led to late programmed cell death that was accounted for by the progression of cells into the cell cycle as shown by (a) the accumulation of apoptotic cells in the G(2)-M phase at 10(-3) m pNO treatment; and (b) the prevention of cell death by inhibiting the entry of cells into the cell cycle. The entry of pNO-treated cells into the G(2)-M phase was associated with actin depolymerization and its S-glutathionylation in the same way as in control cells. However, the pNO treatment interfered with the build-up of a high reducing power, associated in control cells with a dramatic increase in reduced glutathione biosynthesis in the G(2)-M phase. This oxidative stress prevented the exit from the G(2)-M phase, which requires a high reducing power for actin deglutathionylation and its repolymerization. Finally, our demonstration that programmed cell death occurred through a caspase-independent pathway is in line with the context of a nitrosative/oxidative stress. In conclusion, this work, which deciphers the connection between the position of colonic cancer cells in the cell cycle and their sensitivity to NO-induced stress and their programmed cell death, could help optimize anticancer protocols based on NO-donating compounds.

  8. Is cytochrome P450 3A4 regulated by menstrual cycle hormones in control endometrium and endometriosis?

    PubMed

    Piccinato, Carla A; Neme, Rosa M; Torres, Natália; Silvério, Renata; Pazzini, Vanessa Bitencourt; Rosa E Silva, Júlio C; Ferriani, Rui A

    2017-03-01

    The estrogen-metabolizing activities of cytochrome P450 (CYP) enzymes have been implicated in endometriosis. However, their regulation in various sources of endometrial tissue under different hormonal conditions has not been clarified. Our objective was to study the hormone regulation of a specific CYP enzyme, namely CYP3A4, in control (n = 15) and endometriosis patients (n = 42). To this end, we evaluated mRNA expression (using real-time PCR) of CYP3A4 in tissue samples classified according to the phase of menstrual cycle at which they were obtained as confirmed by the related circulating hormone levels. Protein expression was also evaluated by Western Blot. In order to further investigate the hormonal regulation of CYP3A4, stromal cells from ovarian endometriotic lesions were cultured with the prevailing hormones of the distinct phases of the menstrual cycle. We observed that all control and endometriosis tissues express CYP3A4. Nevertheless, changes in CYP3A4 gene expression related to cycle phase were only seen in the control eutopic endometrium and not in samples from endometriosis patients, with an increase in the luteal phase. Stromal cells isolated from ovarian endometriotic lesions expressed CYP3A4 and their exposure to luteal phase-mimicking hormones (estradiol + progesterone) reduced CYP3A4 mRNA in parallel with a diminished expression of the corresponding receptors, estrogen receptor alpha and progesterone receptor. Our findings suggest that steroid hormones are able to regulate CYP3A4 mRNA expression, although the circulating levels of these hormones can only regulate control endometrium and not endometriosis tissues, probably because of dysregulated local steroid concentration in these latter samples.

  9. New low-dose, extended-cycle pills with levonorgestrel and ethinyl estradiol: an evolutionary step in birth control

    PubMed Central

    Nelson, Anita

    2010-01-01

    Aim: To review milestones in development of oral contraceptive pills since their introduction in the US 50 years ago in order to better understand how a new formulation with low-dose estrogen in an extended-cycle pattern fits into the evolution of birth control pills. Methods: This is a review of trends in the development of various birth controls pills and includes data from phase III clinical trials for this new formulation. Results: The first birth control pill was a very high-dose monophasic formulation with the prodrug estrogen mestranol and a first-generation progestin. Over the decades, the doses of hormones have been markedly reduced, and a new estrogen and several different progestins were developed and used in different dosing patterns. The final element to undergo change was the 7-day pill-free interval. Many of these same changes have been made in the development of extended-cycle pill formulation. Conclusion: The newest extended-cycle oral contraceptive formulation with 84 active pills, each containing 20 μg ethinyl estradiol and 100 μg levonorgestrel, represents an important evolution in birth control that incorporates lower doses of estrogen (to reduce side effects and possibly reduce risk of thrombosis), fewer scheduled bleeding episodes (to meet women’s desires for fewer and shorter menses) and the use of low-dose estrogen in place of placebo pills (to reduce the number of days of unscheduled spotting and bleeding). Hopefully, this unique formation will motivate women to be more successful contraceptors. PMID:21072303

  10. Soil Salinity Controls on Water and Carbon Cycling by Sunflower Plants

    NASA Astrophysics Data System (ADS)

    Runkle, B.; Liang, X.; Dracup, J.; Hao, F.; Zeng, A.; Zhang, J.; He, B.; Oki, T.

    2007-12-01

    Agricultural effects on water cycling are of great importance for regional water resources management. These effects vary based on local soil and climate conditions, and are particularly modulated by high soil salinity levels, which stress plant growth and change their water use efficiency. Increasing salinization is predicted under hotter, drier conditions resulting from global climate change and from increased societal pressure on agricultural lands. This increased ionic presence creates a higher soil osmotic pressure that increases the resistance to water flow through the plant. This change also impacts the assimilation of carbon dioxide through the stomatal opening, and so affects rates of both photosynthesis and transpiration. Current agricultural and land-surface models that account for salinity do so in an overly empirical manner that cannot account for changes at different time scales in meteorological conditions. They tend to be ill equipped to examine how changing carbon dioxide levels may modify a plant's response to soil salinity. As a result, we present a new model of soil-vegetation- atmosphere water transfer that explicitly incorporates the role of soil salinity in changing this system's behavior. This model will allow for much greater flexibility in examining how vegetation may change the local water cycle under the joint impacts of both salinity and climate change. This model is supported by field research on the effects of salinity on sunflower plants in a large irrigation district in Inner Mongolia, China. Results presented include the role of salinity in changing stomatal regulation of water use efficiency, sub-canopy changes in leaf pressure, and changes in root activity. Modeling at sub-hourly time scales allows for a more precise understanding of how soil salinity changes the diurnal cycle of plant water use.

  11. Epigenetic control of viral life-cycle by a DNA-methylation dependent transcription factor.

    PubMed

    Flower, Kirsty; Thomas, David; Heather, James; Ramasubramanyan, Sharada; Jones, Susan; Sinclair, Alison J

    2011-01-01

    Epstein-Barr virus (EBV) encoded transcription factor Zta (BZLF1, ZEBRA, EB1) is the prototype of a class of transcription factor (including C/EBPalpha) that interact with CpG-containing DNA response elements in a methylation-dependent manner. The EBV genome undergoes a biphasic methylation cycle; it is extensively methylated during viral latency but is reset to an unmethylated state following viral lytic replication. Zta is expressed transiently following infection and again during the switch between latency and lytic replication. The requirement for CpG-methylation at critical Zta response elements (ZREs) has been proposed to regulate EBV replication, specifically it could aid the activation of viral lytic gene expression from silenced promoters on the methylated genome during latency in addition to preventing full lytic reactivation from the non-methylated EBV genome immediately following infection. We developed a computational approach to predict the location of ZREs which we experimentally assessed using in vitro and in vivo DNA association assays. A remarkably different binding motif is apparent for the CpG and non-CpG ZREs. Computational prediction of the location of these binding motifs in EBV revealed that the majority of lytic cycle genes have at least one and many have multiple copies of methylation-dependent CpG ZREs within their promoters. This suggests that the abundance of Zta protein coupled with the methylation status of the EBV genome act together to co-ordinate the expression of lytic cycle genes at the majority of EBV promoters.

  12. Arsenic control during aquifer storage recovery cycle tests in the Floridan Aquifer.

    PubMed

    Mirecki, June E; Bennett, Michael W; López-Baláez, Marie C

    2013-01-01

    Implementation of aquifer storage recovery (ASR) for water resource management in Florida is impeded by arsenic mobilization. Arsenic, released by pyrite oxidation during the recharge phase, sometimes results in groundwater concentrations that exceed the 10 µg/L criterion defined in the Safe Drinking Water Act. ASR was proposed as a major storage component for the Comprehensive Everglades Restoration Plan (CERP), in which excess surface water is stored during the wet season, and then distributed during the dry season for ecosystem restoration. To evaluate ASR system performance for CERP goals, three cycle tests were conducted, with extensive water-quality monitoring in the Upper Floridan Aquifer (UFA) at the Kissimmee River ASR (KRASR) pilot system. During each cycle test, redox evolution from sub-oxic to sulfate-reducing conditions occurs in the UFA storage zone, as indicated by decreasing Fe(2+) /H2 S mass ratios. Arsenic, released by pyrite oxidation during recharge, is sequestered during storage and recovery by co-precipitation with iron sulfide. Mineral saturation indices indicate that amorphous iron oxide (a sorption surface for arsenic) is stable only during oxic and sub-oxic conditions of the recharge phase, but iron sulfide (which co-precipitates arsenic) is stable during the sulfate-reducing conditions of the storage and recovery phases. Resultant arsenic concentrations in recovered water are below the 10 µg/L regulatory criterion during cycle tests 2 and 3. The arsenic sequestration process is appropriate for other ASR systems that recharge treated surface water into a sulfate-reducing aquifer.

  13. Irrigation and Fertilization Controls on Critical Zone Carbon and Nitrogen cycles in Harvested Ecosystems

    NASA Astrophysics Data System (ADS)

    Parolari, A.; Katul, G. G.; Porporato, A. M.

    2014-12-01

    Feedbacks between hydrology, soil biogeochemistry, and primary productivity raise questions regarding the broader impact of human modifications to one or more of these critical zone processes. In particular, irrigation and nitrogen fertilization are used simultaneously to stimulate agricultural productivity and biomass export; however, together they may lead to unintended downstream consequences such as increased nitrogen leaching or greenhouse gas release. To quantify such trade-offs among ecosystem services and to identify optimal agricultural management practices, an ecosystem model coupling the water, carbon, and nitrogen cycles is studied. The model is forced by stochastic climate and periodic management interventions that include irrigation, fertilization, and harvest. Steady-state solutions of ecosystems under rotational harvest are developed, demonstrating that these ecosystems operate in a limit-cycle. Under constant fertilization and soil moisture conditions, the model predicts an optimal rotation length associated with maximum yield and maximum ecosystem nitrogen use efficiency. Through plant-soil feedbacks mediated by the harvest, intermediate rotation lengths promote short periods of immobilization, which stimulates mineral nitrogen retention. In these systems, increased soil moisture increases non-productive nitrogen losses, especially under long rotations, where mineral nitrogen availability is greatest. Time-variable water and nitrogen input scenarios are also considered and suggest the possibility of an optimal irrigation-fertilization strategy that balances productivity, which provides an economic benefit, and leaching, which may have consequences for aquatic ecosystems in receiving waters. These results highlight several soil C-N cycle responses to management practices that influence the provision of and trade-off between ecosystem services, namely primary productivity and mineral nitrogen export.

  14. A standardized monitor for the control of ethylene oxide sterilization cycles.

    PubMed Central

    Dadd, A. H.; Stewart, C. M.; Town, M. M.

    1983-01-01

    The resistance of spores of B. subtilis var. niger produced in liquid synthetic medium and exposed to ethylene oxide on a nylon surface, has been shown to the almost identical to that for spores produced on a traditional solidified complex medium with exposure to the sterilant on aluminium foil. The use of short lengths of nylon tube as carriers allowed easy production and handling, with self-protection of the spore-bearing surface. Addition of a dye provided visual evidence of inoculation without affecting resistance to ethylene oxide. Such a monitor is suitable for use as a standardized biological challenge in routine ethylene oxide sterilization cycles. PMID:6411808

  15. Climate Controls on European Fluvial Denudation over Glacial-Interglacial Cycles

    NASA Astrophysics Data System (ADS)

    Ehlers, Todd A.; Schaller, Mirjam; Mutz, Sebastian G.

    2017-04-01

    Quaternary climate change between glacial-interglacial cycles is commonly thought to induce variations in catchment denudation rates. However, measurements of temporal variations in fluvial denudation are often lacking. Here we present an integration of existing and new cosmogenic nuclide-derived denudation rates from European river terraces with predicted climate change during glacial and interglacial periods derived from a high-resolution (T159, 80x80km) global atmospheric general circulation model (ECHAM5) . Cosmogenic nuclide concentrations were interpreted from river terraces spanning 12 degrees of latitude in unglaciated, tectonically quiescent settings. 25 analyses of cosmogenic nuclide concentrations provide catchment-wide paleodenudation rates from terraces. From 0.5-2.0 Ma these data indicate low, and constant (< 20 mm/kyr) fluvial paleodenudation rates. Modern cosmogenic nuclide-derived denudation rates are generally higher (20-50 mm/kyr). However, previous higher-fidelity studies of terraces formed since the Last Glacial Maximum (LGM) suggest a factor of 1.5-3 higher denudation rates during the LGM compared to modern. Results from paleoclimate simulations of the LGM, mid-Holocene, and modern times suggest precipitation rates during the last glacial period were 100-500 mm/yr drier than the modern rates across Europe. Mid-Holocene precipitation rates were 100 mm/yr drier (SW Europe) to 200 mm/yr wetter (central Europe) than modern rates. Predicted LGM temperatures indicate periglacial conditions in some areas. Thus, despite moderate changes in predicted precipitation between glacial and interglacial cycles, there is no clear signal of these cycles in cosmogenic nuclide-derived denudation rates between 0.5-2 Ma. In contrast, catchments with higher-fidelity records since the LGM document higher denudation rates during glacial times. We suggest this temporal difference in denudation rates is driven by periglacial, not fluvial, processes. These results have

  16. Environmental Controls on Nitrogen and Sulfur Cycles in Surficial Aquatic Sediments

    PubMed Central

    Gu, Chuanhui; Laverman, Anniet M.; Pallud, Céline E.

    2012-01-01

    Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical cycling in aquatic and terrestrial ecosystems. The N and S cycles interact with one another through competition for labile forms of organic carbon between nitrate-reducing and sulfate-reducing bacteria. Furthermore, the N and S cycles could interact through nitrate (NO3-) reduction coupled to S oxidation, consuming NO3-, and producing sulfate (SO42-). The research questions of this study were: (1) what are the environmental factors explaining variability in N and S biogeochemical reaction rates in a wide range of surficial aquatic sediments when NO3- and SO42- are present separately or simultaneously, (2) how the N and S cycles could interact through S oxidation coupled to NO3- reduction, and (3) what is the extent of sulfate reduction inhibition by nitrate, and vice versa. The N and S biogeochemical reaction rates were measured on intact surface sediment slices using flow-through reactors. The two terminal electron acceptors NO3- and SO42- were added either separately or simultaneously and NO3- and SO42- reduction rates as well as NO3- reduction linked to S oxidation were determined. We used redundancy analysis, to assess how environmental variables were related to these rates. Our analysis showed that overlying water pH and salinity were two dominant environmental factors that explain 58% of the variance in the N and S biogeochemical reaction rates when NO3- and SO42- were both present. When NO3- and SO42- were added separately, however, sediment N content in addition to pH and salinity accounted for 62% of total variance of the biogeochemical reaction rates. The SO42- addition had little effect on NO3- reduction; neither did the NO3- addition inhibit SO42- reduction. The presence of NO3- led to SO42- production most likely due to the oxidation of sulfur. Our observations suggest that metal-bound S, instead of free sulfide produced by SO42- reduction, was responsible

  17. Eddy current control in the AGS rapid cycling booster accelerator magnets

    SciTech Connect

    Danby, G.T.; Jackson, J.W.; Spataro, C.

    1994-07-01

    The Booster requires highly variable magnet cycles. When B is large, eddy current induced sextupole, etc., in the dipole vacuum chamber (VC) is large, with a much smaller contribution from magnet ends. Simple passive coils excited automatically by transformer action cancel the B induced sextupole. A self correction coil is not required for the quadrupoles, since B induced aberrations are very small (< 1.0 {times} 10{sup {minus}4} at full aperture). Iron magnetization does not produce dipole or quadrupole magnet multipole aberrations, so these magnets have been effectively made independent of unwanted multipoles for all cycles. However, variations in the transfer functions and thus the Booster tune have not been automatically eliminated. Iron magnetization contributions are almost matched, but the B induced field retardation in the dipoles VC is larger than in the quadrupoles. Results of measurements will be presented, plus a simple system to overcome the mismatch and make the tune independent of B. Properties of special lattice magnets and their corrections will also be described.

  18. Eddy current control in the AGS rapid cycling booster accelerator magnets

    SciTech Connect

    Danby, G.T.; Jackson, J.W.; Spataro, C.

    1993-11-01

    The Booster requires highly variable magnet cycles. When B is large, eddy current induced sextupole, etc., in the dipole vacuum chamber (VC) is large, with a much smaller contribution from magnet ends. Simple passive coils excited automatically by transformer action cancel the B induced sextupole. A self correction coil is not required for the quadrupoles, since g induced aberrations are very small (< 1.0 {times} 10{sup {minus}4} at full aperture). Iron magnetization does not produce dipole or quadrupole magnet multipole aberrations, so these magnets have been effectively made independent of unwanted multipoles for all cycles. However, variations in the transfer functions and thus the Booster tune have not been automatically eliminated. Iron magnetization contributions are almost matched, but the B induced field retardation in the dipoles VC is larger than in the quadrupoles. Results of measurements will be presented, plus a simple system to overcome the mismatch and make the tune independent of B. Properties of special lattice magnets and their corrections will also be described.

  19. 2000 MCM electrical power jumper cable with controlled flexibility: Design and life cycle test

    SciTech Connect

    Bultman, D.H.; Sims, J.R.; Reass, W.A.

    1989-01-01

    The ZTH Reversed Field Pinch (RFP) plasma confinement experiment being built at the Los Alamos National Laboratory will use magnet coils to provide ohmic heating currents in the plasma. The ohmic heating coils are supported by a structure that will allow them limited movement with respect to surrounding hardware and the connecting electrical bus work. To minimize displacement-induced stresses in the coils, flexible'' power conducting links are necessary to accommodate the relative motion between the bus work and the coils. A semi-flexible 2000 MCM jumper cable has been designed with enough flexibility to allow free movement of the coils, yet it is stiff enough to withstand large magnetically-induced lateral loads and minimize the effect of the lateral loads on the magnet coil leads. A full-power life cycle test of the jumper was performed under magnetic, thermal and dynamic loads that closely simulate the expected operating conditions. This test evaluated the structural and electrical integrity of the jumper as well as the quality and reliability of the bolted electrical connections at the jumper ends in a high-stress, cyclic-loading environment. The jumper cable design is presented with an explanation of the requirements for a semi-flexible link. A description of the life cycle test and test results are given, as well as a description of the test apparatus and setup. 4 figs.

  20. Control of the ornithine cycle in Neurospora crassa by the mitochondrial membrane.

    PubMed Central

    Davis, R H; Ristow, J L

    1983-01-01

    In Neurospora crassa, the mitochondrial membrane separates ornithine used in arginine biosynthesis from ornithine used in the arginine degradative pathway in the cytosol. Ornithine easily exchanges across the mitochondrial membrane under conditions appropriate for synthesis of the immediate biosynthetic product, citrulline. Neither of the two mitochondrial enzymes required for the ornithine-to-citrulline conversion is feedback inhibitable in vitro. Nevertheless, when arginine is added to cells and cytosolic ornithine increases as arginine degradation begins, the rate of citrulline synthesis drops immediately to about 20% of normal (B. J. Bowman and R. H. Davis, Bacteriol. 130:285-291, 1977). We have studied this phenomenon in citrulline-accumulating strains carrying the arg-1 mutation. Citrulline accumulation is blocked when arginine is added to an arg-1 strain but not to an arg-1 strain carrying a mutation conferring insensitivity of intramitochondrial ornithine synthesis to arginine. Thus, ornithine is evidently unable to enter mitochondria in normal (feedback-sensitive) cells. Other experiments show that cytosolic ornithine enters mitochondria readily except when arginine or other basic amino acids are present at high levels in the cells. We conclude that in N. crassa, the mitochondrial membrane has evolved as a secondary site of feedback inhibition in arginine synthesis and that this prevents a wasteful cycling of catabolic ornithine back through the anabolic pathway. This is compared to the quite different mechanism by which the yeast Saccharomyces cerevisiae prevents a futile ornithine cycle. PMID:6222031

  1. Human DNA polymerase alpha gene: sequences controlling expression in cycling and serum-stimulated cells.

    PubMed Central

    Pearson, B E; Nasheuer, H P; Wang, T S

    1991-01-01

    We have investigated the DNA polymerase alpha promoter sequence requirements for the expression of a heterologous gene in actively cycling cells and following serum addition to serum-deprived cells. An 11.4-kb genomic clone that spans the 5' end of this gene and includes 1.62 kb of sequence upstream from the translation start site was isolated. The transcription start site was mapped at 46 +/- 1 nucleotides upstream from the translation start site. The upstream sequence is GC rich and lacks a TATA sequence but has a CCAAT sequence on the opposite strand. Analysis of a set of deletion constructs in transient transfection assays demonstrated that efficient expression of the reporter in cycling cells requires 248 bp of sequence upstream from the cap site. Clustered within these 248 nucleotides are sequences similar to consensus sequences for Sp1-, Ap1-, Ap2-, and E2F-binding sites. The CCAAT sequence and the potential E2F- and Ap1-binding sites are shown to be protected from DNase I digestion by partially purified nuclear proteins. The DNA polymerase alpha promoter can confer upon the reporter an appropriate, late response to serum addition. No single sequence element could be shown to confer serum inducibility. Rather, multiple sequence elements appear to mediate the full serum response. Images PMID:2005899

  2. Oxygen Isotope in Phosphate an Indicator of Phosphorous Cycling in the Ocean - Controls, and Applications

    NASA Astrophysics Data System (ADS)

    Paytan, A.; Roberts, K.; Defforey, D.; McLaughlin, K.; Lomas, M. W.; Church, M. J.; Mackey, K. R.

    2012-12-01

    In order to better constrain the parameters affecting oxygen isotope exchange between water and phosphate via biochemical reactions a set of culture experiments were conducted. Different species of phytoplankton were grown in seawater at various temperatures, light levels, and phosphate concentrations. The oxygen isotopic composition in the phosphate source, algal cells, and the isotopic composition oxygen in the dissolved inorganic phosphate (DIP) were measured. Results showing the effect of species, temperature, light and P availability on intracellular oxygen isotope exchange between phosphorus compounds and water will be presented. The effect of these parameters on the utility of the oxygen isotopic composition of phosphate as a tracer of phosphate utilization rate in the ocean will be discussed. This information is fundamental to any application of isotopic composition of oxygen of dissolved inorganic or organic phosphate to quantify the dynamics of phosphorus cycling in aquatic systems. The data will be utilized to investigate seasonal changes in phosphate sources and cycling in the open ocean and how these relate to phytoplankton abundance, hydrography, and nutrient concentrations.

  3. The C. elegans hox gene lin-39 controls cell cycle progression during vulval development.

    PubMed

    Roiz, Daniel; Escobar-Restrepo, Juan Miguel; Leu, Philipp; Hajnal, Alex

    2016-10-01

    Cell fate specification during organogenesis is usually followed by a phase of cell proliferation to produce the required number of differentiated cells. The Caenorhabditis elegans vulva is an excellent model to study how cell fate specification and cell proliferation are coordinated. The six vulval precursor cells (VPCs) are born at the first larval stage, but they arrest in the G1 phase of the cell cycle until the beginning of the third larval stage, when their fates are specified and the three proximal VPCs proliferate to generate 22 vulval cells. An epidermal growth factor (EGF) signal from the gonadal anchor cell combined with lateral DELTA/NOTCH signaling between the VPCs determine the primary (1°) and secondary (2°) fates, respectively. The hox gene lin-39 plays a key role in integrating these spatial patterning signals and in maintaining the VPCs as polarized epithelial cells. Using a fusion-defective eff-1(lf) mutation to keep the VPCs polarized, we find that VPCs lacking lin-39 can neither activate lateral NOTCH signaling nor proliferate. LIN-39 promotes cell cycle progression through two distinct mechanisms. First, LIN-39 maintains the VPCs competent to proliferate by inducing cdk-4 cdk and cye-1 cyclinE expression via a non-canonical HOX binding motif. Second, LIN-39 activates in the adjacent VPCs the NOTCH signaling pathway, which promotes VPC proliferation independently of LIN-39. The hox gene lin-39 is therefore a central node in a regulatory network coordinating VPC differentiation and proliferation.

  4. Substrate Utilization and Cycling Performance Following Palatinose™ Ingestion: A Randomized, Double-Blind, Controlled Trial.

    PubMed

    König, Daniel; Zdzieblik, Denise; Holz, Anja; Theis, Stephan; Gollhofer, Albert

    2016-06-23

    (1) OBJECTIVE: To compare the effects of isomaltulose (Palatinose™, PSE) vs. maltodextrin (MDX) ingestion on substrate utilization during endurance exercise and subsequent time trial performance; (2) METHODS: 20 male athletes performed two experimental trials with ingestion of either 75 g PSE or MDX 45 min before the start of exercise. The exercise protocol consisted of 90 min cycling (60% VO₂max) followed by a time trial; (3) RESULTS: Time trial finishing time (-2.7%, 90% CI: ±3.0%, 89% likely beneficial; p = 0.147) and power output during the final 5 min (+4.6%, 90% CI: ±4.0%, 93% likely beneficial; p = 0.053) were improved with PSE compared with MDX. The blood glucose profile differed between trials (p = 0.013) with PSE resulting in lower glycemia during rest (95%-99% likelihood) and higher blood glucose concentrations during exercise (63%-86% likelihood). In comparison to MDX, fat oxidation was higher (88%-99% likelihood; p = 0.005) and carbohydrate oxidation was lower following PSE intake (85%-96% likelihood; p = 0.002). (4) CONCLUSION: PSE maintained a more stable blood glucose profile and higher fat oxidation during exercise which resulted in improved cycling performance compared with MDX. These results could be explained by the slower availability and the low-glycemic properties of Palatinose™ allowing a greater reliance on fat oxidation and sparing of glycogen during the initial endurance exercise.

  5. Substrate Utilization and Cycling Performance Following Palatinose™ Ingestion: A Randomized, Double-Blind, Controlled Trial

    PubMed Central

    König, Daniel; Zdzieblik, Denise; Holz, Anja; Theis, Stephan; Gollhofer, Albert

    2016-01-01

    (1) Objective: To compare the effects of isomaltulose (Palatinose™, PSE) vs. maltodextrin (MDX) ingestion on substrate utilization during endurance exercise and subsequent time trial performance; (2) Methods: 20 male athletes performed two experimental trials with ingestion of either 75 g PSE or MDX 45 min before the start of exercise. The exercise protocol consisted of 90 min cycling (60% VO2max) followed by a time trial; (3) Results: Time trial finishing time (−2.7%, 90% CI: ±3.0%, 89% likely beneficial; p = 0.147) and power output during the final 5 min (+4.6%, 90% CI: ±4.0%, 93% likely beneficial; p = 0.053) were improved with PSE compared with MDX. The blood glucose profile differed between trials (p = 0.013) with PSE resulting in lower glycemia during rest (95%–99% likelihood) and higher blood glucose concentrations during exercise (63%–86% likelihood). In comparison to MDX, fat oxidation was higher (88%–99% likelihood; p = 0.005) and carbohydrate oxidation was lower following PSE intake (85%–96% likelihood; p = 0.002). (4) Conclusion: PSE maintained a more stable blood glucose profile and higher fat oxidation during exercise which resulted in improved cycling performance compared with MDX. These results could be explained by the slower availability and the low-glycemic properties of Palatinose™ allowing a greater reliance on fat oxidation and sparing of glycogen during the initial endurance exercise. PMID:27347996

  6. A translation-like cycle is a quality control checkpoint for maturing 40S ribosome subunits.

    PubMed

    Strunk, Bethany S; Novak, Megan N; Young, Crystal L; Karbstein, Katrin

    2012-07-06

    Assembly factors (AFs) prevent premature translation initiation on small (40S) ribosomal subunit assembly intermediates by blocking ligand binding. However, it is unclear how AFs are displaced from maturing 40S ribosomes, if or how maturing subunits are assessed for fidelity, and what prevents premature translation initiation once AFs dissociate. Here we show that maturation involves a translation-like cycle whereby the translation factor eIF5B, a GTPase, promotes joining of large (60S) subunits with pre-40S subunits to give 80S-like complexes, which are subsequently disassembled by the termination factor Rli1, an ATPase. The AFs Tsr1 and Rio2 block the mRNA channel and initiator tRNA binding site, and therefore 80S-like ribosomes lack mRNA or initiator tRNA. After Tsr1 and Rio2 dissociate from 80S-like complexes Rli1-directed displacement of 60S subunits allows for translation initiation. This cycle thus provides a functional test of 60S subunit binding and the GTPase site before ribosomes enter the translating pool.

  7. Impact of modeled microgravity on migration, differentiation, and cell cycle control of primitive human hematopoietic progenitor cells.

    PubMed

    Plett, P Artur; Abonour, Rafat; Frankovitz, Stacy M; Orschell, Christie M

    2004-08-01

    Migration, proliferation, and differentiation of bone marrow (BM) hematopoietic stem cells (HSC) are important factors in maintaining hematopoietic homeostasis. Homeostatic control of erythrocytes and lymphocytes is perturbed in humans exposed to microgravity (micro-g), resulting in space flight-induced anemia and immunosuppression. We sought to determine whether any of these anomalies can be explained by micro-g-induced changes in migration, proliferation, and differentiation of human BM CD34+ cells, and whether such changes can begin to explain any of the shifts in hematopoietic homeostasis observed in astronauts. BM CD34+ cells were cultured in modeled micro-g (mmicro-g) using NASA's rotating wall vessels (RWV), or in control cultures at earth gravity for 2 to 18 days. Cells were harvested at different times and CD34+ cells assessed for migration potential, cell-cycle kinetics and regulatory proteins, and maturation status. Culture of BM CD34+ cells in RWV for 2 to 3 days resulted in a significant reduction of stromal cell-derived factor 1 (SDF-1alpha)-directed migration, which correlated with decreased expression of F-actin. Modeled micro-g induced alterations in cell-cycle kinetics that were characterized by prolonged S phase and reduced cyclin A expression. Differentiation of primitive CD34+ cells cultured for 14 to 18 days in RWV favored myeloid cell development at the expense of erythroid development, which was significantly reduced compared to controls. These results illustrate that mmicro-g significantly inhibits the migration potential, cell-cycle progression, and differentiation patterns of primitive BM CD34+ cells, which may contribute to some of the hematologic abnormalities observed in humans during space flight.

  8. Physiological and hydrological controls on mineral redox cycling by long-range electron transport by bacteria in anaerobic sediments

    NASA Astrophysics Data System (ADS)

    Michelson, K.; Werth, C. J.; Sanford, R. A.; Valocchi, A. J.

    2016-12-01

    The cycling of iron and manganese oxides plays a critical role in the bioavailability of trace elements and macronutrients, the flux of carbon across terrestrial and atmospheric ecosystems, and the remediation of groundwater contaminated by toxic metals and radionuclides. Bacteria control one half of the redox cycle as the primary drivers of iron and manganese reduction in anaerobic soils and sediments. However, Fe(III) and Mn(IV) are almost exclusively present under anaerobic conditions as insoluble oxides, the reduction of which are facilitated by extracellular electron transport via conductive `nanowires', electron shuttling, and direct contact with outer membrane cytochromes. Our research focus is on the relative contribution of nanowires and electron shuttles under different physiological and hydrological conditions, which remains unexplored. We present a novel microfluidic platform that allows us to directly observe these phenomena under a controlled environment representative of groundwater conditions, monitor the metabolic activity and redox state of bacteria, and determine the presence of reduced products in-situ using Raman spectroscopy. Using Geobacter sulfurreducens and Shewanella oneidensis as model metal-reducing bacteria, and insoluble manganese dioxide (i.e. birnessite) as an electron acceptor, we show that 1) electron shuttling is more effective under static conditions 2) the presence of exogenous shuttles allows efficient electron transport under all flow regimes 3) redox potential of the bulk medium exerts significant control over reduction by both nanowires and electron shuttles 4) shuttling is amplified by orders of magnitude in nanopores.

  9. Recruitment of Cln3 Cyclin to Promoters Controls Cell Cycle Entry via Histone Deacetylase and Other Targets

    PubMed Central

    Cai, Ying; Wijnen, Herman; Futcher, Bruce

    2009-01-01

    In yeast, the G1 cyclin Cln3 promotes cell cycle entry by activating the transcription factor SBF. In mammals, there is a parallel system for cell cycle entry in which cyclin dependent kinase (CDK) activates transcription factor E2F/Dp. Here we show that Cln3 regulates SBF by at least two different pathways, one involving the repressive protein Whi5, and the second involving Stb1. The Rpd3 histone deacetylase complex is also involved. Cln3 binds to SBF at the CLN2 promoter, and removes previously bound Whi5 and histone deacetylase. Adding extra copies of the SBF binding site to the cell delays Start, possibly by titrating Cln3. Since Rpd3 is the yeast ortholog of mammalian HDAC1, there is now a virtually complete analogy between the proteins regulating cell cycle entry in yeast (SBF, Cln3, Whi5 and Stb1, Rpd3) and mammals (E2F, Cyclin D, Rb, HDAC1). The cell may titrate Cln3 molecules against the number of SBF binding sites, and this could be the underlying basis of the size-control mechanism for Start. PMID:19823669

  10. Live-cell monitoring of periodic gene expression in synchronous human cells identifies Forkhead genes involved in cell cycle control

    PubMed Central

    Grant, Gavin D.; Gamsby, Joshua; Martyanov, Viktor; Brooks, Lionel; George, Lacy K.; Mahoney, J. Matthew; Loros, Jennifer J.; Dunlap, Jay C.; Whitfield, Michael L.

    2012-01-01

    We developed a system to monitor periodic luciferase activity from cell cycle–regulated promoters in synchronous cells. Reporters were driven by a minimal human E2F1 promoter with peak expression in G1/S or a basal promoter with six Forkhead DNA-binding sites with peak expression at G2/M. After cell cycle synchronization, luciferase activity was measured in live cells at 10-min intervals across three to four synchronous cell cycles, allowing unprecedented resolution of cell cycle–regulated gene expression. We used this assay to screen Forkhead transcription factors for control of periodic gene expression. We confirmed a role for FOXM1 and identified two novel cell cycle regulators, FOXJ3 and FOXK1. Knockdown of FOXJ3 and FOXK1 eliminated cell cycle–dependent oscillations and resulted in decreased cell proliferation rates. Analysis of genes regulated by FOXJ3 and FOXK1 showed that FOXJ3 may regulate a network of zinc finger proteins and that FOXK1 binds to the promoter and regulates DHFR, TYMS, GSDMD, and the E2F binding partner TFDP1. Chromatin immunoprecipitation followed by high-throughput sequencing analysis identified 4329 genomic loci bound by FOXK1, 83% of which contained a FOXK1-binding motif. We verified that a subset of these loci are activated by wild-type FOXK1 but not by a FOXK1 (H355A) DNA-binding mutant. PMID:22740631

  11. On the use of lenses to focus few-cycle pulses with controlled carrier-envelope phase

    NASA Astrophysics Data System (ADS)

    Porras, M. A.; Horvath, Z. L.; Major, B.

    2012-09-01

    From a model of focusing with lenses that includes the effects of the lens variable thickness, material dispersion, aperture, spherical and chromatic aberrations, we characterize the conditions under which a lens can focus to few-cycle, transform-limited pulses propagating without distortion along the focal region. A lens also allows to control the carrier-envelope phase shift along the focus. The carrier-envelope phase shift is drastically reduced by focusing with specific focal lengths and input spot sizes, which are of the same order as those typically used in experiments involving focusing for phase-sensitive, light-matter interactions.

  12. Walking cycle control for an active ankle prosthesis with one degree of freedom monitored from a personal computer.

    PubMed

    Cordero Andrés, Guzhñay; Arévalo Luis, Calle; Abad Julio, Zambrano

    2015-08-01

    This paper proposes a fuzzy control algorithm for human walking cycle of an active ankle prosthesis for people who have suffered amputation of the lower limb, the system has one degree of freedom in the sagittal plane. Also, a biomechanical analysis of foot and ankle is shown to define the phases of plantar support and swinging. The used actuator is an intelligent servomotor, Dynamixel MX-106T which has torque, current and position feedback, among others, allowing real-time telemetry of the prototype implemented in a microcontroller system.

  13. Thermodynamic and dynamic controls on changes in the zonally anomalous hydrological cycle

    NASA Astrophysics Data System (ADS)

    Wills, Robert C.; Byrne, Michael P.; Schneider, Tapio

    2016-05-01

    The wet gets wetter, dry gets drier paradigm explains the expected moistening of the extratropics and drying of the subtropics as the atmospheric moisture content increases with global warming. Here we show, using precipitation minus evaporation (P - E) data from climate models, that it cannot be extended to apply regionally to deviations from the zonal mean. Wet and dry zones shift substantially in response to shifts in the stationary-eddy circulations that cause them. Additionally, atmospheric circulation changes lead to a smaller increase in the zonal variance of P - E than would be expected from atmospheric moistening alone. The P - E variance change can be split into dynamic and thermodynamic components through an analysis of the atmospheric moisture budget. This reveals that a weakening of stationary-eddy circulations and changes in the zonal variation of transient-eddy moisture fluxes moderate the strengthening of the zonally anomalous hydrological cycle with global warming.

  14. Host plant peptides elicit a transcriptional response to control the Sinorhizobium meliloti cell cycle during symbiosis.

    PubMed

    Penterman, Jon; Abo, Ryan P; De Nisco, Nicole J; Arnold, Markus F F; Longhi, Renato; Zanda, Matteo; Walker, Graham C

    2014-03-04

    The α-proteobacterium Sinorhizobium meliloti establishes a chronic intracellular infection during the symbiosis with its legume hosts. Within specialized host cells, S. meliloti differentiates into highly polyploid, enlarged nitrogen-fixing bacteroids. This differentiation is driven by host cells through the production of defensin-like peptides called "nodule-specific cysteine-rich" (NCR) peptides. Recent research has shown that synthesized NCR peptides exhibit antimicrobial activity at high concentrations but cause bacterial endoreduplication at sublethal concentrations. We leveraged synchronized S. meliloti populations to determine how treatment with a sublethal NCR peptide affects the cell cycle and physiology of bacteria at the molecular level. We found that at sublethal levels a representative NCR peptide specifically blocks cell division and antagonizes Z-ring function. Gene-expression profiling revealed that the cell division block was produced, in part, through the substantial transcriptional response elicited by sublethal NCR treatment that affected ∼15% of the genome. Expression of critical cell-cycle regulators, including ctrA, and cell division genes, including genes required for Z-ring function, were greatly attenuated in NCR-treated cells. In addition, our experiments identified important symbiosis functions and stress responses that are induced by sublethal levels of NCR peptides and other antimicrobial peptides. Several of these stress-response pathways also are found in related α-proteobacterial pathogens and might be used by S. meliloti to sense host cues during infection. Our data suggest a model in which, in addition to provoking stress responses, NCR peptides target intracellular regulatory pathways to drive S. meliloti endoreduplication and differentiation during symbiosis.

  15. Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Kohfeld, Karen E.; Chase, Zanna

    2017-08-01

    Many mechanisms have been proposed to explain the ∼85-90 ppm decrease in atmospheric carbon dioxide (CO2) during the last glacial cycle, between 127,000 and 18,000 yrs ago. When taken together, these mechanisms can, in some models, account for the full glacial-interglacial CO2 drawdown. Most proxy-based evaluations focus on the peak of the Last Glacial Maximum, 24,000-18,000 yrs ago, and little has been done to determine the sequential timing of processes affecting CO2 during the last glacial cycle. Here we use a new compilation of sea-surface temperature records together with time-sequenced records of carbon and Nd isotopes, and other proxies to determine when the most commonly proposed mechanisms could have been important for CO2 drawdown. We find that the initial major drawdown of 35 ppm 115,000 yrs ago was most likely a result of Antarctic sea ice expansion. Importantly, changes in deep ocean circulation and mixing did not play a major role until at least 30,000 yrs after the first CO2 drawdown. The second phase of CO2 drawdown occurred ∼70,000 yrs ago and was also coincident with the first significant influences of enhanced ocean productivity due to dust. Finally, minimum concentrations of atmospheric CO2 during the Last Glacial Maximum resulted from the combination of physical and biological factors, including the barrier effect of expanded Southern Ocean sea ice, slower ventilation of the deep sea, and ocean biological feedbacks.

  16. Identifying sources and processes controlling the sulphur cycle in the Canyon Creek watershed, Alberta, Canada.

    PubMed

    Nightingale, Michael; Mayer, Bernhard

    2012-01-01

    Sources and processes affecting the sulphur cycle in the Canyon Creek watershed in Alberta (Canada) were investigated. The catchment is important for water supply and recreational activities and is also a source of oil and natural gas. Water was collected from 10 locations along an 8 km stretch of Canyon Creek including three so-called sulphur pools, followed by the chemical and isotopic analyses on water and its major dissolved species. The δ(2)H and δ(18)O values of the water plotted near the regional meteoric water line, indicating a meteoric origin of the water and no contribution from deeper formation waters. Calcium, magnesium and bicarbonate were the dominant ions in the upstream portion of the watershed, whereas sulphate was the dominant anion in the water from the three sulphur pools. The isotopic composition of sulphate (δ(34)S and δ(18)O) revealed three major sulphate sources with distinct isotopic compositions throughout the catchment: (1) a combination of sulphate from soils and sulphide oxidation in the bedrock in the upper reaches of Canyon Creek; (2) sulphide oxidation in pyrite-rich shales in the lower reaches of Canyon Creek and (3) dissolution of Devonian anhydrite constituting the major sulphate source for the three sulphur pools in the central portion of the watershed. The presence of H(2)S in the sulphur pools with δ(34)S values ∼30 ‰ lower than those of sulphate further indicated the occurrence of bacterial (dissimilatory) sulphate reduction. This case study reveals that δ(34)S values of surface water systems can vary by more than 20 ‰ over short geographic distances and that isotope analyses are an effective tool to identify sources and processes that govern the sulphur cycle in watersheds.

  17. Ergometer-cycling with strict versus minimal contact supervision among the oldest adults: A cluster-randomised controlled trial.

    PubMed

    Van Roie, Evelien; Martien, Sofie; Hurkmans, Emalie; Pelssers, Johan; Seghers, Jan; Boen, Filip; Delecluse, Christophe

    To evaluate the feasibility and short- and long-term effects of two 10-wk structured ergometer-cycling programs among elderly in assisted-living residences. Eight assisted-living residences (N=95; age=81.2±5.9years) were randomly assigned to one of three conditions: 1) ergometer-cycling with strict coach-supervision (STRICT, N=3; n=35); 2) ergometer-cycling with autonomy-supportive minimal contact coach-supervision (AUT; N=3; n=36); or 3) control condition (CON; N=2, n=24). Three-weekly progressive ergometer-cycling sessions for 10 weeks. Feasibility, physical activity (PA), muscular strength, functional performance and quality of life (baseline, post-intervention (10weeks) and 6-month follow-up). 83 participants were analyzed post-intervention, 75 at follow-up. Adherence was higher in STRICT than AUT during the intervention (p=0.001), but not during follow-up. Compared with CON, both programs showed positive short- and long-term effects on moderate-intensity PA (p=0.034). With regard to strength, functional performance and well-being, no time-by-group interaction effects were found. When comparing high-adherers (adherence≥80%) to low-adherers, a greater increase in functional performance and in well-being and a trend towards a lower decrease in strength were found in the short-term (p=0.047, p<0.001 and p=0.054, respectively). Both interventions were feasible and equally effective to increase long-term engagement in PA, irrespective of the type of supervision. When adherence is high, positive effects on strength, performance and well-being can be expected. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Interleaved DC-DC Converter with Discrete Duty Cycle and Open Loop Control

    NASA Astrophysics Data System (ADS)

    Kroics, K.; Sokolovs, A.

    2016-08-01

    The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM) but close to boundary conduction mode (BCM). The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.

  19. Autonomic regulation across phases of the menstrual cycle and sleep stages in women with premenstrual syndrome and healthy controls.

    PubMed

    de Zambotti, Massimiliano; Nicholas, Christian L; Colrain, Ian M; Trinder, John A; Baker, Fiona C

    2013-11-01

    To investigate the influence of menstrual cycle phase and the presence of severe premenstrual symptoms on cardiac autonomic control during sleep, we performed heart rate variability (HRV) analysis during stable non-rapid eye movement (NREM) and REM sleep in 12 women with severe premenstrual syndrome and 14 controls in the mid-follicular, mid-luteal, and late-luteal phases of the menstrual cycle. Heart rate was higher, along with lower high frequency (HF) power, reflecting reduced vagal activity, and a higher ratio of low frequency (LF) to high frequency power, reflecting a shift to sympathetic dominance, in REM sleep compared with NREM sleep in both groups of women. Both groups of women had higher heart rate during NREM and REM sleep in the luteal phase recordings compared with the mid-follicular phase. HF power in REM sleep was lowest in the mid-luteal phase, when progesterone was highest, in both groups of women. The mid-luteal phase reduction in HF power was also evident in NREM sleep in control women but not in women with PMS, suggesting some impact of premenstrual syndrome on autonomic responses to the hormone environment of the mid-luteal phase. In addition, mid-luteal phase progesterone levels correlated positively with HF power and negatively with LF/HF ratio in control women in NREM sleep and with the LF/HF ratio during REM sleep in both groups of women. Our findings suggest the involvement of female reproductive steroids in cardiac autonomic control during sleep in women with and without premenstrual syndrome.

  20. 78 FR 79328 - Amendments to Material Control and Accounting Regulations and Proposed Guidance for Fuel Cycle...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-30

    ... weather and extending the public comment period for a proposed rule and draft guidance on material control... rule and proposed guidance on December 10, 2013. Due to inclement weather, this public meeting has been...

  1. Predictive control strategy of a gas turbine for improvement of combined cycle power plant dynamic performance and efficiency.

    PubMed

    Mohamed, Omar; Wang, Jihong; Khalil, Ashraf; Limhabrash, Marwan

    2016-01-01

    This paper presents a novel strategy for implementing model predictive control (MPC) to a large gas turbine power plant as a part of our research progress in order to improve plant thermal efficiency and load-frequency control performance. A generalized state space model for a large gas turbine covering the whole steady operational range is designed according to subspace identification method with closed loop data as input to the identification algorithm. Then the model is used in developing a MPC and integrated into the plant existing control strategy. The strategy principle is based on feeding the reference signals of the pilot valve, natural gas valve, and the compressor pressure ratio controller with the optimized decisions given by the MPC instead of direct application of the control signals. If the set points for the compressor controller and turbine valves are sent in a timely manner, there will be more kinetic energy in the plant to release faster responses on the output and the overall system efficiency is improved. Simulation results have illustrated the feasibility of the proposed application that has achieved significant improvement in the frequency variations and load following capability which are also translated to be improvements in the overall combined cycle thermal efficiency of around 1.1 % compared to the existing one.

  2. Novel Design Integrating a Microwave Applicator into a Crystallizer for Rapid Temperature Cycling. A Direct Nucleation Control Study

    PubMed Central

    2017-01-01

    The control of nucleation in crystallization processes is a challenging task due to the often lacking knowledge on the process kinetics. Inflexible (predetermined) control strategies fail to grow the nucleated crystals to the desired quality because of the variability in the process conditions, disturbances, and the stochastic nature of crystal nucleation. Previously, the concept of microwave assisted direct nucleation control (DNC) was demonstrated in a laboratory setup to control the crystal size distribution in a batch crystallization process by manipulating the number of particles in the system. Rapid temperature cycling was used to manipulate the super(under)saturation and hence the number of crystals. The rapid heating response achieved with the microwave heating improved the DNC control efficiency, resulting in halving of the batch time. As an extension, this work presents a novel design in which the microwave applicator is integrated in the crystallizer, hence avoiding the external loop though the microwaves oven. DNC implemented in the 4 L unseeded crystallizer, at various count set points, resulted in strong efficiency enhancement of DNC, when compared to the performance with a slow responding system. The demonstrated crystallizer design is a basis for extending the enhanced process control opportunity to other applications. PMID:28729813

  3. The mind-tranquilizing and menstruation-regulating method for acupuncture treatment of delayed menstrual cycle--a clinical controlled study.

    PubMed

    Cai, Xue-mei; Wu, Jie

    2009-03-01

    To compare the therapeutic effects of the mind-tranquilizing and menstruation-regulating acupuncture method with the routine acupuncture method in treating delayed menstrual cycle. 40 patients with delayed menstrual cycle were randomly divided into a treatment group of 23 cases (treated by the mind-tranquilizing and menstruation-regulating acupuncture method), and a control group of 17 cases (treated by the routine acupuncture method for delayed menstrual cycle due to stagnation of the liver-qi). The treatment involved three menstrual cycles. The evaluations were done by scoring the symptoms before treatment and at the end of each menstrual cycle. After treatment, significant differences were found between the two groups in the therapeutic effects (P<0.05). The therapeutic effect of the mind-tranquilizing and menstruation-regulating acupuncture method is significantly superior to that of the routine acupuncture method for delayed menstrual cycle.

  4. Open cycle ocean thermal energy conversion steam control and bypass system

    DOEpatents

    Wittig, J. Michael; Jennings, Stephen J.

    1980-01-01

    Two sets of hinged control doors for regulating motive steam flow from an evaporator to a condenser alternatively through a set of turbine blades in a steam bypass around the turbine blades. The evaporator has a toroidal shaped casing situated about the turbine's vertical axis of rotation and an outlet opening therein for discharging motive steam into an annular steam flow path defined between the turbine's radially inner and outer casing structures. The turbine blades extend across the steam flow path intermediate the evaporator and condenser. The first set of control doors is arranged to prevent steam access to the upstream side of the turbine blades and the second set of control doors acts as a bypass around the blades so as to maintain equilibrium between the evaporator and condenser during non-rotation of the turbine. The first set of control doors preferably extend, when closed, between the evaporator casing and the turbine's outer casing and, when open, extend away from the axis of rotation. The second set of control doors preferably constitute a portion of the turbine's outer casing downstream from the blades when closed and extend, when open, toward the axis of rotation. The first and second sets of control doors are normally held in the open and closed positions respectively by locking pins which may be retracted upon detecting an abnormal operating condition respectively to permit their closing and opening and provide steam flow from the evaporator to the condenser.

  5. A General G1/S-Phase Cell-Cycle Control Module in the Flowering Plant Arabidopsis thaliana

    PubMed Central

    Zhao, Xin'Ai; Harashima, Hirofumi; Dissmeyer, Nico; Pusch, Stefan; Weimer, Annika K.; Bramsiepe, Jonathan; Bouyer, Daniel; Rademacher, Svenja; Nowack, Moritz K.; Novak, Bela; Sprunck, Stefanie; Schnittger, Arp

    2012-01-01

    The decision to replicate its DNA is of crucial importance for every cell and, in many organisms, is decisive for the progression through the entire cell cycle. A comparison of animals versus yeast has shown that, although most of the involved cell-cycle regulators are divergent in both clades, they fulfill a similar role and the overall network topology of G1/S regulation is highly conserved. Using germline development as a model system, we identified a regulatory cascade controlling entry into S phase in the flowering plant Arabidopsis thaliana, which, as a member of the Plantae supergroup, is phylogenetically only distantly related to Opisthokonts such as yeast and animals. This module comprises the Arabidopsis homologs of the animal transcription factor E2F, the plant homolog of the animal transcriptional repressor Retinoblastoma (Rb)-related 1 (RBR1), the plant-specific F-box protein F-BOX-LIKE 17 (FBL17), the plant specific cyclin-dependent kinase (CDK) inhibitors KRPs, as well as CDKA;1, the plant homolog of the yeast and animal Cdc2+/Cdk1 kinases. Our data show that the principle of a double negative wiring of Rb proteins is highly conserved, likely representing a universal mechanism in eukaryotic cell-cycle control. However, this negative feedback of Rb proteins is differently implemented in plants as it is brought about through a quadruple negative regulation centered around the F-box protein FBL17 that mediates the degradation of CDK inhibitors but is itself directly repressed by Rb. Biomathematical simulations and subsequent experimental confirmation of computational predictions revealed that this regulatory circuit can give rise to hysteresis highlighting the here identified dosage sensitivity of CDK inhibitors in this network. PMID:22879821

  6. Processes Controlling the Seasonal Cycle of Arctic Aerosol Number and Size Distributions

    NASA Astrophysics Data System (ADS)

    Wentworth, G.; Croft, B.; Martin, R.; Leaitch, W. R.; Tunved, P.; Breider, T. J.; D'Andrea, S.; Pierce, J. R.; Murphy, J. G.; Kodros, J.; Abbatt, J.

    2015-12-01

    Measurements at high-Arctic sites show a strong seasonal cycle in aerosol number and size. The number of aerosols with diameters larger than 20 nm exhibits a maximum in late spring associated with a dominant accumulation mode, and a second maximum in the summer associated with a dominant Aitken mode. Seasonal-mean aerosol effective diameter ranges from about 160 nm in summer to 250 nm in winter. This study interprets these seasonal cycles with the GEOS-Chem-TOMAS global aerosol microphysics model. We find improved agreement with in situ measurements (SMPS) of aerosol size at both Alert, Nunavut, and Mt. Zeppelin, Svalbard following model developments: 1) increase the efficiency of wet scavenging in the Arctic summer and 2) represent coagulation between interstitial aerosols and aerosols activated to form cloud droplets. Our simulations indicate that the dominant summer-time Aitken mode is associated with increased efficiency of wet removal, which limits the number of larger aerosols and promotes local new-aerosol formation. We also find an important role of interstitial coagulation in clouds in the Arctic, which limits the number of Aitken-mode aerosols in the non-summer seasons when direct wet removal of these aerosols is inefficient. The summertime Arctic atmosphere is particularly pristine and strongly influenced by natural regional emissions which have poorly understood climate impacts. Especially influenced are the climatic roles of atmospheric particles and clouds. Here we present evidence that ammonia (NH3) emissions from migratory-seabird guano (dung) are the primary contributor to summertime free ammonia levels recently measured in the Canadian Arctic atmosphere. These findings suggest that ammonia from seabird guano is a key factor contributing to bursts of new-particle formation, which are observed every summer in the near-surface atmosphere at Alert, Canada. Chemical transport model simulations show that these newly formed particles can grow by vapour

  7. SAS-4 Protein in Trypanosoma brucei Controls Life Cycle Transitions by Modulating the Length of the Flagellum Attachment Zone Filament.

    PubMed

    Hu, Huiqing; Zhou, Qing; Li, Ziyin

    2015-12-18

    The evolutionarily conserved centriole/basal body protein SAS-4 regulates centriole duplication in metazoa and basal body duplication in flagellated and ciliated organisms. Here, we report that the SAS-4 homolog in the flagellated protozoan Trypanosoma brucei, TbSAS-4, plays an unusual role in controlling life cycle transitions by regulating the length of the flagellum attachment zone (FAZ) filament, a specialized cytoskeletal structure required for flagellum adhesion and cell morphogenesis. TbSAS-4 is concentrated at the distal tip of the FAZ filament, and depletion of TbSAS-4 in the trypomastigote form disrupts the elongation of the new FAZ filament, generating cells with a shorter FAZ associated with a longer unattached flagellum and repositioned kinetoplast and basal body, reminiscent of epimastigote-like morphology. Further, we show that TbSAS-4 associates with six additional FAZ tip proteins, and depletion of TbSAS-4 disrupts the enrichment of these FAZ tip proteins at the new FAZ tip, suggesting a role of TbSAS-4 in maintaining the integrity of this FAZ tip protein complex. Together, these results uncover a novel function of TbSAS-4 in regulating the length of the FAZ filament to control basal body positioning and life cycle transitions in T. brucei.

  8. The light cycle controls the hatching rhythm in Bombyx mori via negative feedback loop of the circadian oscillator.

    PubMed

    Tao, Hui; Li, Xue; Qiu, Jian-Feng; Liu, Heng-Jiang; Zhang, Da-Yan; Chu, Feng; Sima, Yanghu; Xu, Shi-Qing

    2017-10-01

    Hatching behavior is a key target in silkworm (Bombyx mori) rearing, especially for the control of Lepidoptera pests. According to previous research, hatching rhythms appear to be controlled by a clock mechanism that restricts or "gates" hatching to a particular time. However, the underlying mechanism remains elusive. Under 12-h light:12-h dark photoperiod (LD) conditions, the transcriptional levels of the chitinase5 (Cht5) and hatching enzyme-like (Hel) genes, as well as the enzymatic activities of their gene products, oscillated in time with ambient light cycles, as did the transcriptional levels of the cryptochrome 1, cryptochrome 2, period (per), and timeless genes, which are key components of the negative feedback loop of the circadian rhythm. These changes were related to the expression profile of the ecdysteroid receptor gene and the hatching behavior of B. mori eggs. However, under continuous light or dark conditions, the hatching behavior, the expression levels of Cht5 and Hel, as well as the enzymatic activities of their gene products, were not synchronized unlike under LD conditions. In addition, immunohistochemistry experiments showed that light promoted the translocation of PER from the cytoplasm to the nucleus. In conclusion, LD cycles regulate the hatching rhythm of B. mori via negative feedback loop of the circadian oscillator. © 2017 Wiley Periodicals, Inc.

  9. Physiological electric fields control the G1/S phase cell cycle checkpoint to inhibit endothelial cell proliferation.

    PubMed

    Wang, Entong; Yin, Yili; Zhao, Min; Forrester, John V; McCaig, Colin D

    2003-03-01

    Vascular endothelial cell (VEC) proliferation is a key event in angiogenesis and is tightly regulated. Electric potential differences exist around the vascular endothelium and give rise to endogenous electric fields (EFs), whether these EFs influence VEC proliferation is unclear. We exposed cultured VECs to applied EFs of physiological strengths for up to 72 h. EF at 50 or 100 mV/mm did not influence cell proliferation, but at 200 mV/mm, cell density, cell growth rate, and mitosis index decreased significantly. EF-induced reduction in VEC proliferation was not due to increased apoptosis, because caspase apoptosis inhibitor Z-VAD-FMK (20 microM), had no effect on this response. Rather, EF responses were mediated via decreased entry of cells into S phase from G1 phase, as shown by flow cytometry. Western blot showed that EFs decreased G1-specific cyclin E expression and increased cyclin/cyclin-dependent kinase complex inhibitor p27kipl expression. Thus EFs controlled VEC proliferation through induction of cell cycle arrest at G1 by down-regulation of cyclin E expression and up-regulation of p27kipl expression, rather than by promoting apoptosis. If control of the cell cycle by endogenous EFs extends beyond VECs, this would be of widespread biological significance in vivo.

  10. Dual-harmonic auto voltage control for the rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

    NASA Astrophysics Data System (ADS)

    Tamura, Fumihiko; Schnase, Alexander; Yoshii, Masahito

    2008-07-01

    The dual-harmonic operation, in which the accelerating cavities are driven by the superposition of the fundamental and the second harmonic rf voltage, is useful for acceleration of the ultrahigh intensity proton beam in the rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC). However, the precise and fast voltage control of the harmonics is necessary to realize the dual-harmonic acceleration. We developed the dual-harmonic auto voltage control system for the J-PARC RCS. We describe details of the design and the implementation. Various tests of the system are performed with the RCS rf system. Also, a preliminary beam test has been done. We report the test results.

  11. An acetylation/deacetylation cycle controls the export of sterols and steroids from S. cerevisiae

    PubMed Central

    Tiwari, Rashi; Köffel, René; Schneiter, Roger

    2007-01-01

    Sterol homeostasis in eukaryotic cells relies on the reciprocal interconversion of free sterols and steryl esters. Here we report the identification of a novel reversible sterol modification in yeast, the sterol acetylation/deacetylation cycle. Sterol acetylation requires the acetyltransferase ATF2, whereas deacetylation requires SAY1, a membrane-anchored deacetylase with a putative active site in the ER lumen. Lack of SAY1 results in the secretion of acetylated sterols into the culture medium, indicating that the substrate specificity of SAY1 determines whether acetylated sterols are secreted from the cells or whether they are deacetylated and retained. Consistent with this proposition, we find that acetylation and export of the steroid hormone precursor pregnenolone depends on its acetylation by ATF2, but is independent of SAY1-mediated deacetylation. Cells lacking Say1 or Atf2 are sensitive against the plant-derived allylbenzene eugenol and both Say1 and Atf2 affect pregnenolone toxicity, indicating that lipid acetylation acts as a detoxification pathway. The fact that homologues of SAY1 are present in the mammalian genome and functionally substitute for SAY1 in yeast indicates that part of this pathway has been evolutionarily conserved. PMID:18034159

  12. Orbital control of western North America atmospheric circulation and climate over two glacial cycles.

    PubMed

    Lachniet, Matthew S; Denniston, Rhawn F; Asmerom, Yemane; Polyak, Victor J

    2014-05-02

    The now arid Great Basin of western North America hosted expansive late Quaternary pluvial lakes, yet the climate forcings that sustained large ice age hydrologic variations remain controversial. Here we present a 175,000 year oxygen isotope record from precisely-dated speleothems that documents a previously unrecognized and highly sensitive link between Great Basin climate and orbital forcing. Our data match the phasing and amplitudes of 65°N summer insolation, including the classic saw-tooth pattern of global ice volume and on-time terminations. Together with the observation of cold conditions during the marine isotope substage 5d glacial inception, our data document a strong precessional-scale Milankovitch forcing of southwestern paleoclimate. Because the expansion of pluvial lakes was associated with cold glacial conditions, the reappearance of large lakes in the Great Basin is unlikely until ca. 55,000 years into the future as climate remains in a mild non-glacial state over the next half eccentricity cycle.

  13. Evaluating microalgal integrated biorefinery schemes: empirical controlled growth studies and life cycle assessment.

    PubMed

    Soh, Lindsay; Montazeri, Mahdokht; Haznedaroglu, Berat Z; Kelly, Cuchulain; Peccia, Jordan; Eckelman, Matthew J; Zimmerman, Julie B

    2014-01-01

    Two freshwater and two marine microalgae species were grown under nitrogen replete and deplete conditions evaluating the impact on total biomass yield and biomolecular fractions (i.e. starch, protein, and lipid). A life cycle assessment was performed to evaluate varying species/growth conditions considering each biomass fraction and final product substitution based on energy consumption, greenhouse gas emissions (GHG), and eutrophication potential. Lipid for biodiesel was assumed as the primary product. Protein and carbohydrate fractions were processed as co-products. Composition of the non-lipid fraction presented significant trade-offs among biogas production, animal feed substitution, nutrient recycling, and carbon sequestration. Maximizing total lipid productivity rather than lipid content yielded the least GHG emissions. A marine, N-deplete case with relatively low lipid productivity but effective nutrient recycling had the lowest eutrophication impacts. Tailoring algal species/growth conditions to optimize the mix of biomolecular fractions matched to desired products and co-products can enable a sustainable integrated microalgal biorefinery. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Magnetic Properties of Bermuda Rise Sediments Controlled by Glacial Cycles During the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Roud, S.

    2015-12-01

    Sediments from ODP site 1063 (Bermuda Rise, North Atlantic) contain a high-resolution record of geomagnetic field behavior during the Brunhes Chron. We present rock magnetic data of the upper 160 mcd (<900 ka) from hole 1063D that show magnetic properties vary in concert with glacial cycles. Magnetite appears to be the main magnetic carrier in the carbonate-dominated interglacial horizons, yet exhibits contrasting grain size distributions depending on the redox state of the horizons. Higher contributions of single domain magnetite exist above the present day sulfate reduction zone (ca. 44 mcd) with relatively higher multidomain magnetite components below that likely arise from the partial dissolution of SD magnetite in the deeper, anoxic horizons. Glacial horizons on the other hand, characterized by enhanced terrigenous deposition, show no evidence for diagenetic dissolution but do indicate the presence of authigenic greigite close to glacial maxima (acquisition of gyro-remanence, strong magnetostatic interactions and SD properties). Glacial horizons contain hematite (maxima in HIRM and S-Ratio consistent with a reddish hue) and exhibit higher ARM anisotropy and pronounced sedimentary fabrics. We infer that post depositional processes affected the magnetic grain size and mineralogy of Bermuda rise sediments deposited during the late Pleistocene. Hematite concentration is interpreted to reflect primary terrigenous input that is likely derived from the Canadian Maritime Provinces. A close correlation between HIRM and magnetic foliation suggests that changes in sediment composition (terrigenous vs. marine biogenic) were accompanied by changes in the depositional processes at the site.

  15. Orbital control of western North America atmospheric circulation and climate over two glacial cycles

    NASA Astrophysics Data System (ADS)

    Lachniet, Matthew S.; Denniston, Rhawn F.; Asmerom, Yemane; Polyak, Victor J.

    2014-05-01

    The now arid Great Basin of western North America hosted expansive late Quaternary pluvial lakes, yet the climate forcings that sustained large ice age hydrologic variations remain controversial. Here we present a 175,000 year oxygen isotope record from precisely-dated speleothems that documents a previously unrecognized and highly sensitive link between Great Basin climate and orbital forcing. Our data match the phasing and amplitudes of 65°N summer insolation, including the classic saw-tooth pattern of global ice volume and on-time terminations. Together with the observation of cold conditions during the marine isotope substage 5d glacial inception, our data document a strong precessional-scale Milankovitch forcing of southwestern paleoclimate. Because the expansion of pluvial lakes was associated with cold glacial conditions, the reappearance of large lakes in the Great Basin is unlikely until ca. 55,000 years into the future as climate remains in a mild non-glacial state over the next half eccentricity cycle.

  16. Polycomb proteins control proliferation and transformation independently of cell cycle checkpoints by regulating DNA replication.

    PubMed

    Piunti, Andrea; Rossi, Alessandra; Cerutti, Aurora; Albert, Mareike; Jammula, Sriganesh; Scelfo, Andrea; Cedrone, Laura; Fragola, Giulia; Olsson, Linda; Koseki, Haruhiko; Testa, Giuseppe; Casola, Stefano; Helin, Kristian; d'Adda di Fagagna, Fabrizio; Pasini, Diego

    2014-04-14

    The ability of PRC1 and PRC2 to promote proliferation is a main feature that links polycomb (PcG) activity to cancer. PcGs silence the expression of the tumour suppressor locus Ink4a/Arf, whose products positively regulate pRb and p53 functions. Enhanced PcG activity is a frequent feature of human tumours, and PcG inhibition has been proposed as a strategy for cancer treatment. However, the recurrent inactivation of pRb/p53 responses in human cancers raises a question regarding the ability of PcG proteins to affect cellular proliferation independently from this checkpoint. Here we demonstrate that PRCs regulate cellular proliferation and transformation independently of the Ink4a/Arf-pRb-p53 pathway. We provide evidence that PRCs localize at replication forks, and that loss of their function directly affects the progression and symmetry of DNA replication forks. Thus, we have identified a novel activity by which PcGs can regulate cell proliferation independently of major cell cycle restriction checkpoints.

  17. Thermochemical cycles

    NASA Technical Reports Server (NTRS)

    Funk, J. E.; Soliman, M. A.; Carty, R. H.; Conger, W. L.; Cox, K. E.; Lawson, D.

    1975-01-01

    The thermochemical production of hydrogen is described along with the HYDRGN computer program which attempts to rate the various thermochemical cycles. Specific thermochemical cycles discussed include: iron sulfur cycle; iron chloride cycle; and hybrid sulfuric acid cycle.

  18. A novel ascaroside controls the parasitic life cycle of the entomopathogenic nematode Heterorhabditis bacteriophora.

    PubMed

    Noguez, Jaime H; Conner, Elizabeth S; Zhou, Yue; Ciche, Todd A; Ragains, Justin R; Butcher, Rebecca A

    2012-06-15

    Entomopathogenic nematodes survive in the soil as stress-resistant infective juveniles that seek out and infect insect hosts. Upon sensing internal host cues, the infective juveniles regurgitate bacterial pathogens from their gut that ultimately kill the host. Inside the host, the nematode develops into a reproductive adult and multiplies until unknown cues trigger the accumulation of infective juveniles. Here, we show that the entomopathogenic nematode Heterorhabditis bacteriophora uses a small-molecule pheromone to control infective juvenile development. The pheromone is structurally related to the dauer pheromone ascarosides that the free-living nematode Caenorhabditis elegans uses to control its development. However, none of the C. elegans ascarosides are effective in H. bacteriophora, suggesting that there is a high degree of species specificity. Our report is the first to show that ascarosides are important regulators of development in a parasitic nematode species. An understanding of chemical signaling in parasitic nematodes may enable the development of chemical tools to control these species.

  19. Asymptotic study of a complete magnetic attitude control cycle providing a single-axis orientation

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.

    2012-08-01

    The angular motion of an axisymmetrical satellite equipped with the active magnetic attitude control system is examined. Attitude control system has to ensure necessary orientation of the axis of symmetry in the inertial space. It implements the following strategy: coarse reorientation of the axis of symmetry with nutation damping or "-Bdot" without initial detumbling; spinning-up about the axis of symmetry to achieve the property of a gyro; fine reorientation of the axis in the inertial space. Dynamics of the satellite is analytically studied using averaging technique on the complete control loop consisting of five algorithms. Solutions of the equations of motion are obtained in terms of quadratures for most cases or even in closed-form. The latter allowed to study the dependence of motion parameters including time-response with respect to the orbit inclination and other parameters for all algorithms.

  20. Cycle scheduling for in vitro fertilization with oral contraceptive pills versus oral estradiol valerate: a randomized, controlled trial

    PubMed Central

    2013-01-01

    Background Both oral contraceptive pills (OCPs) and estradiol (E2) valerate have been used to schedule gonadotropin-releasing hormone (GnRH) antagonist in vitro fertilization (IVF) cycles and, consequently, laboratory activities. However, there are no studies comparing treatment outcomes directly between these two pretreatment methods. This randomized controlled trial was aimed at finding differences in ongoing pregnancy rates between GnRH antagonist IVF cycles scheduled with OCPs or E2 valerate. Methods Between January and May 2012, one hundred consecutive patients (nonobese, regularly cycling women 18–38 years with normal day 3 hormone levels and <3 previous IVF/ICSI attempts) undergoing IVF with the GnRH antagonist protocol were randomized to either the OCP or E2 pretreatment arms, with no restrictions such as blocking or stratification. Authors involved in data collection and analysis were blinded to group assignment. Fifty patients received OCP (30 μg ethinyl E2/150 μg levonorgestrel) for 12–16 days from day 1 or 2, and stimulation was started 5 days after stopping OCP. Similarly, 50 patients received 4 mg/day oral E2 valerate from day 20 for 5–12 days, until the day before starting stimulation. Results Pretreatment with OCP (mean±SD, 14.5±1.7 days) was significantly longer than with E2 (7.8±1.9 days). Stimulation and embryological characteristics were similar. Ongoing pregnancy rates (46.0% vs. 44.0%; risk difference, –2.0% [95% CI –21.2% to 17.3%]), as well as implantation (43.5% vs. 47.4%), clinical pregnancy (50.0% vs. 48.0%), clinical miscarriage (7.1% vs. 7.7%), and live birth (42.0% vs. 40.0%) rates were comparable between groups. Conclusions This is the first study to directly compare these two methods of cycle scheduling in GnRH antagonist cycles. Our results fail to show statistically significant differences in ongoing pregnancy rates between pretreatment with OCP and E2 for IVF with the GnRH antagonist protocol. Although the

  1. Dynamics and control modeling of the closed-cycle gas turbine (GT-HTGR) power plant

    SciTech Connect

    Bardia, A.

    1980-02-01

    The simulation if presented for the 800-MW(e) two-loop GT-HTGR plant design with the REALY2 transient analysis computer code, and the modeling of control strategies called for by the inherently unique operational requirements of a multiple loop GT-HTGR is described. Plant control of the GT-HTGR is constrained by the nature of its power conversion loops (PCLs) in which the core cooling flow and the turbine flow are directly related and thus changes in flow affect core cooling as well as turbine power. Additionally, the high thermal inertia of the reactor core precludes rapid changes in the temperature of the turbine inlet flow.

  2. Re-examination of sea lamprey control policies for the St. Marys River: Completion of an adaptive management cycle

    USGS Publications Warehouse

    Jones, Michael L.; Brenden, Travis O.; Irwin, Brian J.

    2015-01-01

    The St. Marys River (SMR) historically has been a major producer of sea lampreys (Petromyzon marinus) in the Laurentian Great Lakes. In the early 2000s, a decision analysis (DA) project was conducted to evaluate sea lamprey control policies for the SMR; this project suggested that an integrated policy of trapping, sterile male releases, and Bayluscide treatment was the most cost-effective policy. Further, it concluded that formal assessment of larval sea lamprey abundance and distribution in the SMR would be valuable for future evaluation of control strategies. We updated this earlier analysis, adding information from annual larval assessments conducted since 1999 and evaluating additional control policies. Bayluscide treatments continued to be critical for sea lamprey control, but high recruitment compensation minimized the effectiveness of trapping and sterile male release under current feasible ranges. Because Bayluscide control is costly, development of strategies to enhance trapping success remains a priority. This study illustrates benefits of an adaptive management cycle, wherein models inform decisions, are updated based on learning achieved from those decisions, and ultimately inform future decisions.

  3. Life cycle of Puccinia crupinae, a candidate fungal biological control agent for Crupina vulgaris

    USDA-ARS?s Scientific Manuscript database

    Crupina vulgaris (Common crupina, Asteraceae) is an introduced weed pest in the western United States. An isolate of the rust fungus Puccinia crupinae from the Greece is currently under evaluation as a candidate for biological control of C. crupina in a Biosafety Level 3 (BL-3) containment greenhou...

  4. System controls challenges of hypersonic combined-cycle engine powered vehicles

    NASA Technical Reports Server (NTRS)

    Morrison, Russell H.; Ianculescu, George D.

    1992-01-01

    Hypersonic aircraft with air-breathing engines have been described as the most complex and challenging air/space vehicle designs ever attempted. This is particularly true for aircraft designed to accelerate to orbital velocities. The propulsion system for the National Aerospace Plane will be an active factor in maintaining the aircraft on course. Typically addressed are the difficulties with the aerodynamic vehicle design and development, materials limitations and propulsion performance. The propulsion control system requires equal materials limitations and propulsion performance. The propulsion control system requires equal concern. Far more important than merely a subset of propulsion performance, the propulsion control system resides at the crossroads of trajectory optimization, engine static performance, and vehicle-engine configuration optimization. To date, solutions at these crossroads are multidisciplinary and generally lag behind the broader performance issues. Just how daunting these demands will be is suggested. A somewhat simplified treatment of the behavioral characteristics of hypersonic aircraft and the issues associated with their air-breathing propulsion control system design are presented.

  5. Episodic particle transport events controlling PAH and PCB cycling in Grand Traverse Bay, Lake Michigan.

    PubMed

    Schneider, Abby R; Eadie, Brian J; Baker, Joel E

    2002-03-15

    To evaluate the influence of episodic events on particle and hydrophobic organic contaminant (HOC) cycling in the Great Lakes, we deployed sequencing sediment traps at two locations in the western arm of Grand Traverse Bay, Lake Michigan. The traps collected integrated samples of settling particles every 2 weeks from May 1997 to September 1999. The total polycyclic aromatic hydrocarbon (t-PAH) and total polychlorinated biphenyl (t-PCB) settling fluxes from the surface waters in the southern site were significantly greater than those from the northern site. In addition, there were more frequent brief increases in the mass flux to the southern site than to the northern site. These episodic events, which occurred only 20% of the time, accounted for 65% of both the mass flux and t-PAH flux. The t-PCB flux was not influenced by these episodic events, and only 18% of the t-PCB flux occurred during these events. PAHs and PCBs appear to be tracing different types of particles in the water column. Several large mass flux events characteristic of seiches were observed simultaneously in the benthic nepheloid layer (BNL) at both the northern and the southern sites. The particles settling as a result of these resuspension events had lower t-PCB and t-PAH concentrations than particles settling at other times. This suggests that the material settling into the traps on the high mass flux days is composed of a mixture of the less contaminated underlying resuspended sediment and the "regular" contaminant-rich particles settling into the BNL.

  6. Carbon Cycle in South China Sea: Flux, Controls and Global Implications

    NASA Astrophysics Data System (ADS)

    Dai, M.; Cao, Z.; Yang, W.; Guo, X.; Yin, Z.; Gan, J.

    2016-12-01

    The contemporary coastal ocean is generally seen as a significant CO2 sink of 0.2-0.4 Pg C/yr at the global scale. However, mechanistic understanding of the coastal ocean carbon cycle remains limited, leading to the unanswered question of why some coastal systems are sources while others are sinks of atmospheric CO2. As the largest marginal sea of Northern Pacific, the South China Sea (SCS) is a mini-ocean with wide shelves in both its southern and northern parts. Its northern shelf, which receives significant land inputs from the Pearl River, a world major river, can be categorized as a River-Dominated Margin (RioMar) during peak discharges, and is characterized as a CO2 sink to the atmosphere. The SCS basin is identified as an Ocean-Dominated Margin (OceMar) and a CO2 source. OceMar is characterized by exchange with the open ocean via a two-dimensional (at least) process, i.e., the horizontal intrusion of open ocean water and subsequent vertical mixing and upwelling. Depending on the different ratios of dissolved inorganic carbon (DIC) and nutrients from the source waters into the continental margins, the relative consumption or removal bwtween DIC and nutrients, when being transported into the euphotic zones where biogeochemical processes take over, determines the CO2 fluxes. Thus, excess DIC relative to nutrients existing in the upper layer will lead to CO2 degassing. The CO2 fluxes in both RioMars and OceMars can be quantified using a semi-analytical diagnostic approach by coupling the physical dynamics and biogeochemical processes. We extended our mechanistic studies in the SCS to other OceMars including the Caribbean Sea, the Arabian Sea, and the upwelling system off the Oregon-California coast, and RioMars including the East China Sea and Amazon River plume to demonstrate the global implications of our SCS carbon studies.

  7. Cell Cycle Control of a Holdfast Attachment Gene in Caulobacter crescentus

    PubMed Central

    Janakiraman, Raji S.; Brun, Yves V.

    1999-01-01

    Attachment to surfaces by the prosthecate bacterium Caulobacter crescentus is mediated by an adhesive organelle, the holdfast, found at the tip of the stalk. Indirect evidence suggested that the holdfast first appears at the swarmer pole of the predivisional cell. We used fluorescently labeled lectin and transmission electron microscopy to detect the holdfast in different cell types. While the holdfast was readily detectable in stalked cells and at the stalked poles of predivisional cells, we were unable to detect the holdfast in swarmer cells or at the flagellated poles of predivisional cells. This suggests that exposure of the holdfast to the outside of the cell occurs during the differentiation of swarmer to stalked cells. To investigate the timing of holdfast synthesis and exposure to the outside of the cell, we have examined the regulation of a holdfast attachment gene, hfaA. The hfaA gene is part of a cluster of four genes (hfaABDC), identified in strain CB2A and involved in attachment of the holdfast to the polar region of the cell. We have identified the hfaA gene in the synchronizable C. crescentus strain CB15. The sequence of the CB2A hfaA promoter suggested that it was regulated by ς54. We show that the transcription of hfaA from either strain is not dependent on ς54. Using a hfaA-lacZ fusion, we show that the transcription of hfaA is temporally regulated during the cell cycle, with maximal expression in late-predivisional cells. This increase in expression is largely due to the preferential transcription of hfaA in the swarmer pole of the predivisional cell. PMID:9973336

  8. A Plant Cryptochrome Controls Key Features of the Chlamydomonas Circadian Clock and Its Life Cycle.

    PubMed

    Müller, Nico; Wenzel, Sandra; Zou, Yong; Künzel, Sandra; Sasso, Severin; Weiß, Daniel; Prager, Katja; Grossman, Arthur; Kottke, Tilman; Mittag, Maria

    2017-05-01

    Cryptochromes are flavin-binding proteins that act as blue light receptors in bacteria, fungi, plants, and insects and are components of the circadian oscillator in mammals. Animal and plant cryptochromes are evolutionarily divergent, although the unicellular alga Chlamydomonas reinhardtii (Chlamydomonas throughout) has both an animal-like cryptochrome and a plant cryptochrome (pCRY; formerly designated CPH1). Here, we show that the pCRY protein accumulates at night as part of a complex. Functional characterization of pCRY was performed based on an insertional mutant that expresses only 11% of the wild-type pCRY level. The pcry mutant is defective for central properties of the circadian clock. In the mutant, the period is lengthened significantly, ultimately resulting in arrhythmicity, while blue light-based phase shifts show large deviations from what is observed in wild-type cells. We also show that pCRY is involved in gametogenesis in Chlamydomonas pCRY is down-regulated in pregametes and gametes, and in the pcry mutant, there is altered transcript accumulation under blue light of the strictly light-dependent, gamete-specific gene GAS28 pCRY acts as a negative regulator for the induction of mating ability in the light and for the loss of mating ability in the dark. Moreover, pCRY is necessary for light-dependent germination, during which the zygote undergoes meiosis that gives rise to four vegetative cells. In sum, our data demonstrate that pCRY is a key blue light receptor in Chlamydomonas that is involved in both circadian timing and life cycle progression. © 2017 American Society of Plant Biologists. All Rights Reserved.

  9. A Synthetic Human Kinase Can Control Cell Cycle Progression in Budding Yeast

    PubMed Central

    Davey, Megan J.; Andrighetti, Heather J.; Ma, Xiaoli; Brandl, Christopher J.

    2011-01-01

    The DDK kinase complex, composed of Cdc7 and Dbf4, is required for S-phase progression. The two component proteins show different degrees of sequence conservation between human and yeast. Here, we determine that Saccharomyces cerevisiae bearing human CDC7 and DBF4 grows comparably to cells with yeast DDK under standard growth conditions. HsDrf1 (a second human Dbf4-like protein) does not support growth, suggesting that HsDbf4 is the true ortholog of ScDbf4. Both human subunits are required to complement yeast cdc7Δ or dbf4Δ due to the inability of human Cdc7 or Dbf4 to interact with the corresponding yeast protein. Flow cytometry indicates normal cell cycle progression for yeast containing human DDK. However, yeast containing human DDK is sensitive to long-term exposure to hydroxyurea and fails to sporulate, suggesting that human DDK substitutes for some, but not all, of yeast DDK’s functions. We mapped the region of Cdc7 required for species-specific function of DDK to the C-terminus of Cdc7 by substituting the yeast C-terminal 55 amino acid residues in place of the equivalent human residues. The resulting hybrid protein supported growth of a cdc7Δ strain only in the presence of ScDBF4. The strain supported by the hybrid CDC7 was not sensitive to HU and formed tetrads. Together, our data indicate that DDK’s targeting of its essential substrate is conserved between species, whereas the interactions within DDK are species specific. PMID:22384342

  10. Strain-Controlled Low-Cycle Fatigue Properties of a Newly Developed Extruded Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Begum, S.; Chen, D. L.; Xu, S.; Luo, Alan A.

    2008-12-01

    To reduce fuel consumption and greenhouse gas emissions, magnesium alloys are being considered for automotive and aerospace applications due to their low density, high specific strength and stiffness, and other attractive traits. Structural applications of magnesium components require low-cycle fatigue (LCF) behavior, since cyclic loading or thermal stresses are often encountered. The aim of this article was to study the cyclic deformation characteristics and evaluate LCF behavior of a recently developed AM30 extruded magnesium alloy. This alloy exhibited a strong cyclic hardening characteristic, with a cyclic strain-hardening exponent of 0.33 compared to the monotonic strain-hardening exponent of 0.15. With increasing total strain amplitude, both plastic strain amplitude and mean stress increased and fatigue life decreased. A significant difference between the tensile and compressive yield stresses occurred, leading to asymmetric hysteresis loops at high strain amplitudes due to twinning in compression and subsequent detwinning in tension. A noticeable change in the modulus was observed due to the pseudoelastic behavior of this alloy. The Coffin-Manson law and Basquin equation could be used to describe the fatigue life. At low strain ratios the alloy showed strong cyclic hardening, which became less significant as the strain ratio increased. The lower the strain ratio, the lower the stress amplitude and mean stress but the higher the plastic strain amplitude, corresponding to a longer fatigue life. Fatigue life also increased with increasing strain rate. Fatigue crack initiation occurred from the specimen surface and crack propagation was mainly characterized by striation-like features. Multiple initiation sites at the specimen surface were observed at higher strain amplitudes.

  11. Linking the climatic and geochemical controls on global soil carbon cycling

    NASA Astrophysics Data System (ADS)

    Doetterl, Sebastian; Stevens, Antoine; Six, Johan; Merckx, Roel; Van Oost, Kristof; Casanova Pinto, Manuel; Casanova-Katny, Angélica; Muñoz, Cristina; Boudin, Mathieu; Zagal Venegas, Erick; Boeckx, Pascal

    2015-04-01

    Climatic and geochemical parameters are regarded as the primary controls for soil organic carbon (SOC) storage and turnover. However, due to the difference in scale between climate and geochemical-related soil research, the interaction of these key factors for SOC dynamics have rarely been assessed. Across a large geochemical and climatic transect in similar biomes in Chile and the Antarctic Peninsula we show how abiotic geochemical soil features describing soil mineralogy and weathering pose a direct control on SOC stocks, concentration and turnover and are central to explaining soil C dynamics at larger scales. Precipitation and temperature had an only indirect control by regulating geochemistry. Soils with high SOC content have low specific potential CO2 respiration rates, but a large fraction of SOC that is stabilized via organo-mineral interactions. The opposite was observed for soils with low SOC content. The observed differences for topsoil SOC stocks along this transect of similar biomes but differing geo-climatic site conditions are of the same magnitude as differences observed for topsoil SOC stocks across all major global biomes. Using precipitation and a set of abiotic geochemical parameters describing soil mineralogy and weathering status led to predictions of high accuracy (R2 0.53-0.94) for different C response variables. Partial correlation analyses revealed that the strength of the correlation between climatic predictors and SOC response variables decreased by 51 - 83% when controlling for geochemical predictors. In contrast, controlling for climatic variables did not result in a strong decrease in the strength of the correlations of between most geochemical variables and SOC response variables. In summary, geochemical parameters describing soil mineralogy and weathering were found to be essential for accurate predictions of SOC stocks and potential CO2 respiration, while climatic factors were of minor importance as a direct control, but are

  12. Development of the ANL plant dynamics code and control strategies for the supercritical carbon dioxide Brayton cycle and code validation with data from the Sandia small-scale supercritical carbon dioxide Brayton cycle test loop.

    SciTech Connect

    Moisseytsev, A.; Sienicki, J. J.

    2011-11-07

    Significant progress has been made in the ongoing development of the Argonne National Laboratory (ANL) Plant Dynamics Code (PDC), the ongoing investigation and development of control strategies, and the analysis of system transient behavior for supercritical carbon dioxide (S-CO{sub 2}) Brayton cycles. Several code modifications have been introduced during FY2011 to extend the range of applicability of the PDC and to improve its calculational stability and speed. A new and innovative approach was developed to couple the Plant Dynamics Code for S-CO{sub 2} cycle calculations with SAS4A/SASSYS-1 Liquid Metal Reactor Code System calculations for the transient system level behavior on the reactor side of a Sodium-Cooled Fast Reactor (SFR) or Lead-Cooled Fast Reactor (LFR). The new code system allows use of the full capabilities of both codes such that whole-plant transients can now be simulated without additional user interaction. Several other code modifications, including the introduction of compressor surge control, a new approach for determining the solution time step for efficient computational speed, an updated treatment of S-CO{sub 2} cycle flow mergers and splits, a modified enthalpy equation to improve the treatment of negative flow, and a revised solution of the reactor heat exchanger (RHX) equations coupling the S-CO{sub 2} cycle to the reactor, were introduced to the PDC in FY2011. All of these modifications have improved the code computational stability and computational speed, while not significantly affecting the results of transient calculations. The improved PDC was used to continue the investigation of S-CO{sub 2} cycle control and transient behavior. The coupled PDC-SAS4A/SASSYS-1 code capability was used to study the dynamic characteristics of a S-CO{sub 2} cycle coupled to a SFR plant. Cycle control was investigated in terms of the ability of the cycle to respond to a linear reduction in the electrical grid demand from 100% to 0% at a rate of 5

  13. A novel ascaroside controls the parasitic life cycle of the entomopathogenic nematode Heterorhabditis bacteriophora

    PubMed Central

    Noguez, Jaime H.; Conner, Elizabeth S.; Zhou, Yue; Ciche, Todd A.; Ragains, Justin R.; Butcher, Rebecca A.

    2012-01-01

    Entomopathogenic nematodes survive in the soil as stress-resistant infective juveniles that seek out and infect insect hosts. Upon sensing internal host cues, the infective juveniles regurgitate bacterial pathogens from their gut that ultimately kill the host. Inside the host, the nematode develops into a reproductive adult and multiplies until unknown cues trigger the accumulation of infective juveniles. Here, we show that the entomopathogenic nematode Heterorhabditis bacteriophora uses a small-molecule pheromone to control infective juvenile development. The pheromone is structurally related to the dauer pheromone ascarosides that the free-living nematode Caenorhabditis elegans uses to control its development. However, none of the C. elegans ascarosides are effective in H. bacteriophora, suggesting that there is a high degree of species specificity. Our report is the first to show that ascarosides are important regulators of development in a parasitic nematode species. An understanding of chemical signaling in parasitic nematodes may enable the development of chemical tools to control these species. PMID:22444073

  14. Loss of Cell Cycle Checkpoint Control in Drosophila Rfc4 Mutants

    PubMed Central

    Krause, Sue A.; Loupart, Marie-Louise; Vass, Sharron; Schoenfelder, Stefan; Harrison, Steve; Heck, Margarete M. S.

    2001-01-01

    Two alleles of the Drosophila melanogaster Rfc4 (DmRfc4) gene, which encodes subunit 4 of the replication factor C (RFC) complex, cause striking defects in mitotic chromosome cohesion and condensation. These mutations produce larval phenotypes consistent with a role in DNA replication but also result in mitotic chromosomal defects appearing either as premature chromosome condensation-like or precocious sister chromatid separation figures. Though the DmRFC4 protein localizes to all replicating nuclei, it is dispersed from chromatin in mitosis. Thus the mitotic defects appear not to be the result of a direct role for RFC4 in chromosome structure. We also show that the mitotic defects in these two DmRfc4 alleles are the result of aberrant checkpoint control in response to DNA replication inhibition or damage to chromosomes. Not all surveillance function is compromised in these mutants, as the kinetochore attachment checkpoint is operative. Intriguingly, metaphase delay is frequently observed with the more severe of the two alleles, indicating that subsequent chromosome segregation may be inhibited. This is the first demonstration that subunit 4 of RFC functions in checkpoint control in any organism, and our findings additionally emphasize the conserved nature of RFC's involvement in checkpoint control in multicellular eukaryotes. PMID:11438670

  15. Loss of cell cycle checkpoint control in Drosophila Rfc4 mutants.

    PubMed

    Krause, S A; Loupart, M L; Vass, S; Schoenfelder, S; Harrison, S; Heck, M M

    2001-08-01

    Two alleles of the Drosophila melanogaster Rfc4 (DmRfc4) gene, which encodes subunit 4 of the replication factor C (RFC) complex, cause striking defects in mitotic chromosome cohesion and condensation. These mutations produce larval phenotypes consistent with a role in DNA replication but also result in mitotic chromosomal defects appearing either as premature chromosome condensation-like or precocious sister chromatid separation figures. Though the DmRFC4 protein localizes to all replicating nuclei, it is dispersed from chromatin in mitosis. Thus the mitotic defects appear not to be the result of a direct role for RFC4 in chromosome structure. We also show that the mitotic defects in these two DmRfc4 alleles are the result of aberrant checkpoint control in response to DNA replication inhibition or damage to chromosomes. Not all surveillance function is compromised in these mutants, as the kinetochore attachment checkpoint is operative. Intriguingly, metaphase delay is frequently observed with the more severe of the two alleles, indicating that subsequent chromosome segregation may be inhibited. This is the first demonstration that subunit 4 of RFC functions in checkpoint control in any organism, and our findings additionally emphasize the conserved nature of RFC's involvement in checkpoint control in multicellular eukaryotes.

  16. The cycle of human herpes simplex virus infection: virus transport and immune control.

    PubMed

    Cunningham, Anthony L; Diefenbach, Russell J; Miranda-Saksena, Monica; Bosnjak, Lidija; Kim, Min; Jones, Cheryl; Douglas, Mark W

    2006-09-15

    After infection of skin or mucosa, herpes simplex virus enters the sensory nerve endings and is conveyed by retrograde axonal transport to the dorsal root ganglion, where the virus develops lifelong latency. Intermittent reactivation, which is spontaneous in humans, leads to anterograde transport of virus particles and proteins to the skin or mucosa, where the virus is shed and/or causes disease. Immune control of viral infection and replication occurs at the level of skin or mucosa during initial or recurrent infection and also within the dorsal root ganglion, where immune mechanisms control latency and reactivation. This article examines current views on the mechanisms of retrograde and anterograde transport of the virus in axons and the mechanisms of innate and adaptive immunity that control infection in the skin or mucosa and in the dorsal root ganglion--in particular, the role of interferons, myeloid and plasmacytoid dendritic cells, CD4(+) and CD8(+) T cells, and interferon- gamma and other cytokines, including their significance in the development of vaccines for genital herpes.

  17. Control of Tobacco mosaic virus Movement Protein Fate by CELL-DIVISION-CYCLE Protein481[W][OA

    PubMed Central

    Niehl, Annette; Amari, Khalid; Gereige, Dalya; Brandner, Katrin; Mély, Yves; Heinlein, Manfred

    2012-01-01

    Like many other viruses, Tobacco mosaic virus replicates in association with the endoplasmic reticulum (ER) and exploits this membrane network for intercellular spread through plasmodesmata (PD), a process depending on virus-encoded movement protein (MP). The movement process involves interactions of MP with the ER and the cytoskeleton as well as its targeting to PD. Later in the infection cycle, the MP further accumulates and localizes to ER-associated inclusions, the viral factories, and along microtubules before it is finally degraded. Although these patterns of MP accumulation have been described in great detail, the underlying mechanisms that control MP fate and function during infection are not known. Here, we identify CELL-DIVISION-CYCLE protein48 (CDC48), a conserved chaperone controlling protein fate in yeast (Saccharomyces cerevisiae) and animal cells by extracting protein substrates from membranes or complexes, as a cellular factor regulating MP accumulation patterns in plant cells. We demonstrate that Arabidopsis (Arabidopsis thaliana) CDC48 is induced upon infection, interacts with MP in ER inclusions dependent on the MP N terminus, and promotes degradation of the protein. We further provide evidence that CDC48 extracts MP from ER inclusions to the cytosol, where it subsequently accumulates on and stabilizes microtubules. We show that virus movement is impaired upon overexpression of CDC48, suggesting that CDC48 further functions in controlling virus movement by removal of MP from the ER transport pathway and by promoting interference of MP with microtubule dynamics. CDC48 acts also in response to other proteins expressed in the ER, thus suggesting a general role of CDC48 in ER membrane maintenance upon ER stress. PMID:23027663

  18. Plasma surrounding the global heliosphere at large distances controlled by the solar cycle

    NASA Astrophysics Data System (ADS)

    Dialynas, Konstantinos; Krimigis, Stamatios; Mitchell, Donald; Decker, Robert; Roelof, Edmond

    2016-04-01

    The past decade can be characterized by a series of key, groundbreaking remote energetic neutral atom (ENA) images (INCA, IBEX) and in-situ ion (Voyager 1 & 2) observations concerning the characteristics and interactions of the heliosphere with the Local Interstellar Medium (LISM). Voyagers 1 and 2 (V1, V2) discovered the reservoir of ions and electrons that constitute the heliosheath (HS) after crossing the termination shock (TS) 35deg north and 32deg south of the ecliptic plane at 94 and 84 astronomical units (1 AU= 1.5 x108 km), respectively. The in situ measurements by each Voyager were placed in a global context by remote sensing images using ENA obtained with the Ion and Neutral Camera (INCA) onboard Cassini orbiting Saturn. The ENA images contain a 5.2-55 keV hydrogen (H) ENA region (Belt) that loops through the celestial sphere and contributes to balancing the pressure of the interstellar magnetic field (ISMF). The success of any future mission with dedicated ENA detectors (e.g. the IMAP mission), highly depends on the antecedent understanding of the details of the plasma processes in the Heliosphere as revealed by remote sensing of the plasma environment characteristics. Therefore, we address here one of the remaining and most important questions: "Where do the 5-55 keV ENAs that INCA measures come from?". We analyzed INCA all-sky maps from 2003 to 2015 and compare the solar cycle (SC) variation of the ENAs in both the nose (upstream) and anti-nose (downstream) directions with the intensities of > 30 keV ions (source of ENA through charge exchange-CE with H) measured in-situ by V1 and V2, in overlapping energy bands ~30-55 keV. ENA intensities decrease during the declining phase of SC23 by ~x3 from 2003 to 2011 but recover through 2014 (SC24); similarly, V1 and V2 ion intensities also decrease and then recover through 2014. The similarity of time profiles of remotely sensed ENA and locally measured ions are consistent with (a) ENA originating in the HS

  19. Decommissioning of the Hematite Former Fuel Cycle Facility using a decision flow logic based work control process

    SciTech Connect

    Anderson, Keith D.

    2013-07-01

    The remediation and decommissioning of the Hematite Former Fuel Cycle Facility (FFCF), the Hematite Facility, is currently being carried out by Westinghouse Electric Company LLC under the Hematite Decommissioning Project (HDP). The Hematite Facility is located near the town of Hematite, Missouri, USA. The Hematite Facility consists of 228 acres of land with primary operations historically being conducted within the central portion of the property that is roughly 10 acres including Burial Pits and the Site Pond area. Decommissioning and remediation activities are being performed with the eventual objective of the release of the property. Primary contaminants include the legacy disposal and contamination of natural and enriched uranium from the nuclear fuel cycle, as well as chemicals used during the facility operations. Two major regulatory bodies, the U.S. Nuclear Regulatory Commission (NRC) and the Missouri Department of Natural Resources (MDNR), provide critical roles in the approval and oversight of the current regulatory path to remediation, decommissioning and eventual release. Further, remediation and decommissioning activities are performed under the implementing policies, plans, and procedures under the Hematite Decommissioning Plan (DP) and the Record of Decision (ROD). Remediation and decommissioning tasks at the Hematite Former Fuel Cycle Facility, referred to as the Hematite Facility, are performed against a disciplined decision logic flow that applies accumulated technical and monitoring data to determine each step of the excavation, exhumation, and removal of wastes from the Burial Pits and the remaining Areas of Concern (AOC). Decision flow logic is based upon the nuclear criticality safety controls and threshold conditions, relative level of radioactive and chemical contamination, security protocol, and final waste stream disposition. The end result is to remediate the residual radioactive and chemical contamination to approved dose-based and risk

  20. Investigation of Processes Controlling Mercury Cycling at Midlatitudinal Marine and Inland Sites: Improvements and Applications of A Mercury Box Model

    NASA Astrophysics Data System (ADS)

    ye, Z.

    2013-12-01

    Mercury (Hg) is a hazardous pollutant due to the bioaccumulation in food chain. It is emitted to the atmosphere primarily as elemental form, and the long lifetime of which allows global transport. Oxidation of gaseous elemental mercury (GEM) generates reactive gaseous mercury (RGM) which plays an important role in the atmospheric mercury cycle by enhancing the rate of mercury deposition to ecosystem. The present study aimed to investigate the midlatitudinal atmospheric Hg cycling. To achieve that, a mercury chemistry box model was improved by employing the most up-to-date kinetic data for gaseous and aqueous reactions, and was applied to summertime clear sky conditions at three specific sites: Appledore Island (marine site), Thompson Farm (coastal site), and Pack Monadnock (inland site). The model was evaluated using observational data of RGM and pHg (particulate mercury) concentrations from these sites. The simulation results for all three sites showed that HgO, which is produced from oxidation of GEM by O3 and OH, contributed the most (>82%) to the total RGM production. Even in the marine boundary layer, halogen species (mainly Br) only contributed less than 12% to total RGM. The importance of reactions in most updated halogen chemistry has been evaluated. Gas and particle partitioning played an important role in coastal and inland environments. Some abnormally high RGM peaks were found at Appledore Island which may be explained by transport and air-sea exchange. Specific reactions and other processes controlling the diurnal cycles of RGM and pHg at the three sites are still being investigated.

  1. Elucidation of the first definitively identified life cycle for a marine turtle blood fluke (Trematoda: Spirorchiidae) enables informed control.

    PubMed

    Cribb, Thomas H; Crespo-Picazo, Jose L; Cutmore, Scott C; Stacy, Brian A; Chapman, Phoebe A; García-Párraga, Daniel

    2017-01-01

    Blood flukes of the family Spirorchiidae are significant pathogens of both free-ranging and captive marine turtles. Despite a significant proportion of marine turtle mortality being attributable to spirorchiid infections, details of their life cycles remain almost entirely unknown. Here we report on the molecular elucidation of the complete life cycle of a marine spirorchiid, identified as Amphiorchis sp., infecting vermetid gastropods and captive hatched neonate Caretta caretta in the Oceanogràfic Aquarium, in Valencia, Spain. Specimens of a vermetid gastropod, Thylaeodus cf. rugulosus (Monterosato, 1878), collected from the aquarium filtration system housing diseased C. caretta, were infected with sporocysts and cercariae consistent with the family Spirorchiidae. We generated rDNA sequence data [internal transcribed spacer 2 (ITS2) and partial 28S rDNA] from infections from the vermetid which were identical to sequences generated from eggs from the serosa of the intestine of neonate C. caretta, and an adult spirorchiid from the liver of a C. caretta from Florida, USA. Given the reliability of these markers in the delineation of trematode species, we consider all three stages to represent the same species and tentatively identify it as a species of Amphiorchis Price, 1934. The source of infection at the Oceanogràfic Foundation Rehabilitation Centre, Valencia, Spain, is inferred to be an adult C. caretta from the western Mediterranean being rehabilitated in the same facility. Phylogenetic analysis suggests that this Amphiorchis sp. is closely related to other spirorchiids of marine turtles (species of Carettacola Manter & Larson, 1950, Hapalotrema Looss, 1899 and Learedius Price, 1934). We discuss implications of the present findings for the control of spirorchiidiasis in captivity, for the better understanding of epidemiology in wild individuals, and the elucidation of further life cycles. Copyright © 2016 Australian Society for Parasitology. Published by

  2. Variable Cycle Engine Control System Definition Study. Turbine Engine Technology Demonstrator Component Development Program, Project 668A. Controls Development Program

    DTIC Science & Technology

    1976-03-01

    JULY 1973 to MARCH 1976 Approved for public rtlease; distribution unlimited DDC R 191r Alit V0tCE, AKt *IRO-10ROU14,40N LAHIORATf0lty .71 L y ~j Alit...engine parameters to "scheduled" optimal poramelric relationships successfully attained minimum sfc and maximum thrust at all the selected test points in... test plan woa formulated for the JTD control system. Table of Contents Page 1.0 Introduction 1-1 2.0 Summary 2- 1 3.0 Joint Technology Demonstrator

  3. Generation of multiple analog pulses with different duty cycles within VME control system for ICRH Aditya system

    NASA Astrophysics Data System (ADS)

    Joshi, Ramesh; Singh, Manoj; Jadav, H. M.; Misra, Kishor; Kulkarni, S. V.; ICRH-RF Group

    2010-02-01

    Ion Cyclotron Resonance Heating (ICRH) is a promising heating method for a fusion device due to its localized power deposition profile, a direct ion heating at high density, and established technology for high RF power generation and transmission at low cost. Multiple analog pulse with different duty cycle in master of digital pulse for Data acquisition and Control system for steady state RF ICRH System(RF ICRH DAC) to be used for operating of RF Generator in Aditya to produce pre ionization and second analog pulse will produce heating. The control system software is based upon single digital pulse operation for RF source. It is planned to integrate multiple analog pulses with different duty cycle in master of digital pulse for Data acquisition and Control system for RF ICRH System(RF ICRH DAC) to be used for operating of RF Generator in Aditya tokamak. The task of RF ICRH DAC is to control and acquisition of all ICRH system operation with all control loop and acquisition for post analysis of data with java based tool. For pre ionization startup as well as heating experiments using multiple RF Power of different powers and duration. The experiment based upon the idea of using single RF generator to energize antenna inside the tokamak to radiate power twise, out of which first analog pulse will produce pre ionization and second analog pulse will produce heating. The whole system is based on standard client server technology using tcp/ip protocol. DAC Software is based on linux operating system for highly reliable, secure and stable system operation in failsafe manner. Client system is based on tcl/tk like toolkit for user interface with c/c++ like environment which is reliable programming languages widely used on stand alone system operation with server as vxWorks real time operating system like environment. The paper is focused on the Data acquisition and monitoring system software on Aditya RF ICRH System with analog pulses in slave mode with digital pulse in

  4. Controlling factors of spatial and temporal preservation of the geochronological signal in sediments during an orogenic cycle

    NASA Astrophysics Data System (ADS)

    Rat, Juliette; Mouthereau, Frédéric; Bernet, Matthias; Brichau, Stéphanie; Balvay, Mélanie; Garzanti, Eduardo; Ando, Sergio

    2017-04-01

    Detrital content of sediments preserved in basins provide constraints on the nature of source rocks, dynamics of sediment transport, and potentially on tectonics and climate changes. U-Pb dating method on detrital zircon is ideally suited for provenance studies due to the ability of U-Pb age data to resist several orogenic cycles. However, with the aim to track sediment source evolution over a single orogenic cycle and determine characteristic time and parameters controlling the geochronological signal preservation throughout the cycle from rifting, mountain building to post-collision evolution, low-temperature thermochronology combined with sediment petrography are more appropriate than the U-Pb dating approach taken alone. To better understanding processes at play in the long-term geochronological signal preservation we focus on the sediment record associated with the Iberia plate tectonic evolution, which is part of the OROGEN research project, co-financed by BRGM, TOTAL & CNRS. The Iberian plate recorded a period of extension in the Late Jurassic, followed during the Early Cretaceous (Aptian-Albian) by a major thinning event documented by thick syn-rift sediments in intraplate basins and plate-scale heating/cooling of the Iberia crust, as argued by published fission track ages. Paleogeographic reconstructions that are based on stratigraphic and lithofacies analyses in northern Iberia (Iberian Range, Pyrenees and Basque-Cantabrians Range), describe a large domain of continental/fluvial and shallow-marine siliciclastic deposition. The related detrital content was then recycled during the subsequent Pyrenean orogenic phase in the Ebro foreland basin, and eventually transfer to the Mediterranean realm during post-orogenic re-excavation of the Ebro basin. In this study, we complete the published time-temperature paths in the mesozoic syn-rift basins by providing new thermo-chronological analyses of well-dated syn-collision and post-collision stratigraphic sections

  5. The use of a synthetic progesterone, levonorgestrel (LNG), to control the oestrous cycle in the koala.

    PubMed

    Ballantyne, K; Anderson, S T; Pyne, M; Nicolson, V; Mucci, A; Lisle, A; Johnston, S D

    2015-05-01

    This study investigated the efficacy of a synthetic progestogen, levonorgestrel (LNG), to control koala ovarian activity for the purposes of oestrous synchronisation. Captive koalas were administered either saline control or a 70-mg LNG implant on Day 2 of oestrus. Urogenital cytology, oestrous behaviour and plasma oestradiol-17β and LH concentrations were monitored over a 6-week period. After LNG implant removal females were monitored to determine if the return to oestrus was synchronised. LNG-treated koalas immediately ceased displaying oestrous behaviour, showed no evidence of cornified epithelial cells in smears of urogenital cytology and exhibited low plasma oestradiol-17β concentrations throughout the implantation period. In contrast, oestradiol-17β levels in control koalas showed evidence of continued cyclic activity associated with behavioural oestrus and increased cornified epithelial cells in urogenital smears on Days 33 to 35 after saline injection. After implant removal, LNG-treated koalas exhibited oestrus at 13, 14, 17 and 30 days after implant removal. Plasma LH concentrations varied throughout the study period with no significant time (P = 0.49) or treatment (P = 0.13) effect. Overall results from this study suggest that LNG implants in koalas can inhibit oestrous behaviour and reduce circulating oestradiol-17β levels before oestrus, most likely by preventing development of the pre-ovulatory follicle. However, there was no evidence of LH suppression by the LNG implants. Removal of LNG implants resulted in the synchronous return to oestrus in three of the four treated koalas. Further studies on a larger population are required to validate these findings.

  6. Wavefront control to generate ultraviolet supercontinuum by filamentation of few-cycle laser pulses in argon.

    PubMed

    Wang, Zhanxin; Liu, Jiansheng; Li, Ruxin; Xu, Zhizhan

    2010-01-15

    We numerically demonstrated the filamentation dynamics of a 6 fs, 800 nm pulse focused in argon at atmospheric pressure by a zone plate and a concave mirror. In comparison with a concave mirror, the zone plate has a frequency-dependent focal length and can be used to control the wavefront of the laser beam in the frequency domain. A separate supercontinuum in the ultraviolet region extending from 250 to 300 nm and peaked at ~280 nm can be generated by using a proper zone plate.

  7. Micro-RNA-31 controls hair cycle-associated changes in gene expression programs of the skin and hair follicle.

    PubMed

    Mardaryev, Andrei N; Ahmed, Mohammed I; Vlahov, Nikola V; Fessing, Michael Y; Gill, Jason H; Sharov, Andrey A; Botchkareva, Natalia V

    2010-10-01

    The hair follicle is a cyclic biological system that progresses through stages of growth, regression, and quiescence, which involves dynamic changes in a program of gene regulation. Micro-RNAs (miRNAs) are critically important for the control of gene expression and silencing. Here, we show that global miRNA expression in the skin markedly changes during distinct stages of the hair cycle in mice. Furthermore, we show that expression of miR-31 markedly increases during anagen and decreases during catagen and telogen. Administration of antisense miR-31 inhibitor into mouse skin during the early- and midanagen phases of the hair cycle results in accelerated anagen development, and altered differentiation of hair matrix keratinocytes and hair shaft formation. Microarray, qRT-PCR and Western blot analyses revealed that miR-31 negatively regulates expression of Fgf10, the components of Wnt and BMP signaling pathways Sclerostin and BAMBI, and Dlx3 transcription factor, as well as selected keratin genes, both in vitro and in vivo. Using luciferase reporter assay, we show that Krt16, Krt17, Dlx3, and Fgf10 serve as direct miR-31 targets. Thus, by targeting a number of growth regulatory molecules and cytoskeletal proteins, miR-31 is involved in establishing an optimal balance of gene expression in the hair follicle required for its proper growth and hair fiber formation.

  8. APC/C(Cdh1) controls CtIP stability during the cell cycle and in response to DNA damage.

    PubMed

    Lafranchi, Lorenzo; de Boer, Harmen R; de Vries, Elisabeth G E; Ong, Shao-En; Sartori, Alessandro A; van Vugt, Marcel A T M

    2014-12-01

    Human cells have evolved elaborate mechanisms for responding to DNA damage to maintain genome stability and prevent carcinogenesis. For instance, the cell cycle can be arrested at different stages to allow time for DNA repair. The APC/C(C) (dh1) ubiquitin ligase mainly regulates mitotic exit but is also implicated in the DNA damage-induced G2 arrest. However, it is currently unknown whether APC/C(C) (dh1) also contributes to DNA repair. Here, we show that Cdh1 depletion causes increased levels of genomic instability and enhanced sensitivity to DNA-damaging agents. Using an integrated proteomics and bioinformatics approach, we identify CtIP, a DNA-end resection factor, as a novel APC/C(C) (dh1) target. CtIP interacts with Cdh1 through a conserved KEN box, mutation of which impedes ubiquitylation and downregulation of CtIP both during G1 and after DNA damage in G2. Finally, we find that abrogating the CtIP-Cdh1 interaction results in delayed CtIP clearance from DNA damage foci, increased DNA-end resection, and reduced homologous recombination efficiency. Combined, our results highlight the impact of APC/C(C) (dh1) on the maintenance of genome integrity and show that this is, at least partially, achieved by controlling CtIP stability in a cell cycle- and DNA damage-dependent manner.

  9. Biogeochemical and hydrologic processes controlling mercury cycling in Great Salt Lake, Utah

    NASA Astrophysics Data System (ADS)

    Naftz, D.; Kenney, T.; Angeroth, C.; Waddell, B.; Darnall, N.; Perschon, C.; Johnson, W. P.

    2006-12-01

    Great Salt Lake (GSL), in the Western United States, is a terminal lake with a highly variable surface area that can exceed 5,100 km2. The open water and adjacent wetlands of the GSL ecosystem support millions of migratory waterfowl and shorebirds from throughout the Western Hemisphere, as well as a brine shrimp industry with annual revenues exceeding 70 million dollars. Despite the ecologic and economic significance of GSL, little is known about the biogeochemical cycling of mercury (Hg) and no water-quality standards currently exist for this system. Whole water samples collected since 2000 were determined to contain elevated concentrations of total Hg (100 ng/L) and methyl Hg (33 ng/L). The elevated levels of methyl Hg are likely the result of high rates of SO4 reduction and associated Hg methylation in persistently anoxic areas of the lake at depths greater than 6.5 m below the water surface. Hydroacoustic equipment deployed in this anoxic layer indicates a "conveyor belt" flow system that can distribute methyl Hg in a predominantly southerly direction throughout the southern half of GSL (fig. 1, URL: http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs- AUG06.pdf). Periodic and sustained wind events on GSL may result in transport of the methyl Hg-rich anoxic water and bottom sediments into the oxic and biologically active regions. Sediment traps positioned above the anoxic brine interface have captured up to 6 mm of bottom sediment during cumulative wind-driven resuspension events (fig. 2, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Vertical velocity data collected with hydroacoustic equipment indicates upward flow > 1.5 cm/sec during transient wind events (fig. 3, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Transport of methyl Hg into the oxic regions of GSL is supported by biota samples. The median Hg concentration (wet weight) in brine shrimp increased seasonally from the spring to fall time period and is likely a

  10. Early rehabilitation in critical care (eRiCC): functional electrical stimulation with cycling protocol for a randomised controlled trial

    PubMed Central

    Parry, Selina M; Berney, Sue; Koopman, René; Bryant, Adam; El-Ansary, Doa; Puthucheary, Zudin; Hart, Nicholas; Warrillow, Stephen; Denehy, Linda

    2012-01-01

    Introduction Intensive care-acquired weakness is a common problem, leads to significant impairment in physical functioning and muscle strength, and is prevalent in individuals with sepsis. Early rehabilitation has been shown to be safe and feasible; however, commencement is often delayed due to a patient's inability to co-operate. An intervention that begins early in an intensive care unit (ICU) admission without the need for patient volition may be beneficial in attenuating muscle wasting. The eRiCC (early rehabilitation in critical care) trial will investigate the effectiveness of functional electrical stimulation-assisted cycling and cycling alone, compared to standard care, in individuals with sepsis. Methods and analysis This is a single centre randomised controlled trial. Participants (n=80) aged ≥18 years, with a diagnosis of sepsis or severe sepsis, who are expected to be mechanically ventilated for ≥48 h and remain in the intensive care ≥4 days will be randomised within 72 h of admission to (1) standard care or (2) intervention where participants will receive functional electrical muscle stimulation-assisted supine cycling on one leg while the other leg undergoes cycling alone. Primary outcome measures include: muscle mass (quadriceps ultrasonography; bioelectrical impedance spectroscopy); muscle strength (Medical Research Council Scale; hand-held dynamometry) and physical function (Physical Function in Intensive Care Test; Functional Status Score in intensive care; 6 min walk test). Blinded outcome assessors will assess measures at baseline, weekly, at ICU discharge and acute hospital discharge. Secondary measures will be evaluated in a nested subgroup (n=20) and will consist of biochemical/histological analyses of collected muscle, urine and blood samples at baseline and at ICU discharge. Ethics and dissemination Ethics approval has been obtained from the relevant institution, and results will be published to inform clinical practice in

  11. Visceral Leishmaniasis on the Indian Subcontinent: Modelling the Dynamic Relationship between Vector Control Schemes and Vector Life Cycles.

    PubMed

    Poché, David M; Grant, William E; Wang, Hsiao-Hsuan

    2016-08-01

    Visceral leishmaniasis (VL) is a disease caused by two known vector-borne parasite species (Leishmania donovani, L. infantum), transmitted to man by phlebotomine sand flies (species: Phlebotomus and Lutzomyia), resulting in ≈50,000 human fatalities annually, ≈67% occurring on the Indian subcontinent. Indoor residual spraying is the current method of sand fly control in India, but alternative means of vector control, such as the treatment of livestock with systemic insecticide-based drugs, are being evaluated. We describe an individual-based, stochastic, life-stage-structured model that represents a sand fly vector population within a village in India and simulates the effects of vector control via fipronil-based drugs orally administered to cattle, which target both blood-feeding adults and larvae that feed on host feces. Simulation results indicated efficacy of fipronil-based control schemes in reducing sand fly abundance depended on timing of drug applications relative to seasonality of the sand fly life cycle. Taking into account cost-effectiveness and logistical feasibility, two of the most efficacious treatment schemes reduced population peaks occurring from April through August by ≈90% (applications 3 times per year at 2-month intervals initiated in March) and >95% (applications 6 times per year at 2-month intervals initiated in January) relative to no control, with the cumulative number of sand fly days occurring April-August reduced by ≈83% and ≈97%, respectively, and more specifically during the summer months of peak human exposure (June-August) by ≈85% and ≈97%, respectively. Our model should prove useful in a priori evaluation of the efficacy of fipronil-based drugs in controlling leishmaniasis on the Indian subcontinent and beyond.

  12. Visceral Leishmaniasis on the Indian Subcontinent: Modelling the Dynamic Relationship between Vector Control Schemes and Vector Life Cycles

    PubMed Central

    2016-01-01

    Background Visceral leishmaniasis (VL) is a disease caused by two known vector-borne parasite species (Leishmania donovani, L. infantum), transmitted to man by phlebotomine sand flies (species: Phlebotomus and Lutzomyia), resulting in ≈50,000 human fatalities annually, ≈67% occurring on the Indian subcontinent. Indoor residual spraying is the current method of sand fly control in India, but alternative means of vector control, such as the treatment of livestock with systemic insecticide-based drugs, are being evaluated. We describe an individual-based, stochastic, life-stage-structured model that represents a sand fly vector population within a village in India and simulates the effects of vector control via fipronil-based drugs orally administered to cattle, which target both blood-feeding adults and larvae that feed on host feces. Principle findings Simulation results indicated efficacy of fipronil-based control schemes in reducing sand fly abundance depended on timing of drug applications relative to seasonality of the sand fly life cycle. Taking into account cost-effectiveness and logistical feasibility, two of the most efficacious treatment schemes reduced population peaks occurring from April through August by ≈90% (applications 3 times per year at 2-month intervals initiated in March) and >95% (applications 6 times per year at 2-month intervals initiated in January) relative to no control, with the cumulative number of sand fly days occurring April-August reduced by ≈83% and ≈97%, respectively, and more specifically during the summer months of peak human exposure (June-August) by ≈85% and ≈97%, respectively. Conclusions Our model should prove useful in a priori evaluation of the efficacy of fipronil-based drugs in controlling leishmaniasis on the Indian subcontinent and beyond. PMID:27537774

  13. Carbon cycle. Sunlight controls water column processing of carbon in arctic fresh waters.

    PubMed

    Cory, Rose M; Ward, Collin P; Crump, Byron C; Kling, George W

    2014-08-22

    Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget.

  14. p63/p73 in the control of cell cycle and cell death

    SciTech Connect

    Allocati, N.; Di Ilio, C.; De Laurenzi, V.

    2012-07-01

    The p53 family apparently derives from a common ancient ancestor that dates back over a billion years, whose function was protecting the germ line from DNA damage. p63 and p73 would maintain this function through evolution while acquiring novel roles in controlling proliferation and differentiation of various tissues. p53 on the other hand would appear in early vertebrates to protect somatic cells from DNA damage with similar mechanism used by its siblings to protect germ line cells . For the predominant role played by p53 mutations in cancer this was the first family member to be identified and soon became one of the most studied genes. Its siblings were identified almost 20 years later and interestingly enough their ancestral function as guardians of the germ-line was one of the last to be identified. In this review we shortly summarize the current knowledge on the structure and function of p63 and p73.

  15. Dehumidification Performance of Hybrid Type Humidity Control System Coupling a Desiccant Rotor in a Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Horibe, Akihiko; Takaki, Sadao; Inaba, Hideo; Haruki, Naoto

    Desiccant air-conditioning system is a promising technology because the exhaust heat can be effectively used in the future. We have reported the proposed system that combines a desiccant rotor with a vapor compression refrigerator. The confirmation experiment of stability and the performance was conducted with the experimental prototype. The result showed that it had the performance that was necessary for dehumidification driving in the summer and the humidification driving in the winter. In this report, we examined the influence on humidity controlling performance of the processing air temperature and humidity. As a result, we got high dehumidification efficiency and clarified the dehumidification characteristic in dehumidification driving in the summer. Dehumidification efficiency about 4.0 kg/kWh and COP of the system about 2.0 in summer driving mode were obtained.

  16. Epigenetics in Apicomplexa: control of gene expression during cell cycle progression, differentiation and antigenic variation.

    PubMed

    Hakimi, Mohamed-Ali; Deitsch, Kirk W

    2007-08-01

    Apicomplexan parasites are important disease causing organisms that infect both animals and humans, causing extensive health and economic damage to human populations, particularly those in the developing world. The ability to perform genetic crosses, to engineer transgenic parasites lines, and the wealth of information made available through recent genome sequencing projects have made the laboratory study of these parasites important not only for understanding the diseases that they cause, but also for gaining insights into basic biological processes. The control of gene expression and cellular differentiation are particularly interesting in these organisms, as the apparent lack of large families of recognizable transcription factors typically found in other eukaryotic organisms suggests that they may be unusually reliant on epigenetic mechanisms. Here we review recent advances in the study of epigenetic gene regulation in the apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii.

  17. Bioelectric State and Cell Cycle Control of Mammalian Neural Stem Cells

    PubMed Central

    Aprea, Julieta; Calegari, Federico

    2012-01-01

    The concerted action of ion channels and pumps establishing a resting membrane potential has been most thoroughly studied in the context of excitable cells, most notably neurons, but emerging evidences indicate that they are also involved in controlling proliferation and differentiation of nonexcitable somatic stem cells. The importance of understanding stem cell contribution to tissue formation during embryonic development, adult homeostasis, and regeneration in disease has prompted many groups to study and manipulate the membrane potential of stem cells in a variety of systems. In this paper we aimed at summarizing the current knowledge on the role of ion channels and pumps in the context of mammalian corticogenesis with particular emphasis on their contribution to the switch of neural stem cells from proliferation to differentiation and generation of more committed progenitors and neurons, whose lineage during brain development has been recently elucidated. PMID:23024660

  18. U.S. Army combat operational stress control throughout the deployment cycle: a case study.

    PubMed

    Mattila, Amy M; Crandall, Brian D; Goldman, Sarah B

    2011-01-01

    As military conflicts around the world persist, a comprehensive approach in managing behavioral health issues will continue to be a key component of military healthcare. Deployed military personnel frequently exposed to trauma are well-known to be at high risk for developing behavioral health disorders, including combat stress reactions and posttraumatic stress disorder. In the U.S. Army, members of combat operational stress control (COSC) units have unique skills to assist soldiers and their families not only throughout all phases of a deployment, but also throughout a soldier's entire career. The purposes of this article are twofold, first to describe the role of COSC operations with an emphasis on interventions in a deployed environment. The second purpose is to present a case study from Operation Iraqi Freedom highlighting the efficacy of the COSC approach to meet a Soldier's behavioral health needs in a deployed environment.

  19. [Hormonal control of the ovarian cycle in Labidura riparia (author's transl)].

    PubMed

    Caussanel, C; Breuzet, M

    1977-01-01

    The ovaries in female Labidura riparia undergo cyclical development. They require approximately 10 days to complete one vitellogenesis. During this period the Insect eats and and also mates. About 7 to 9 follicles in each ovariole are loaded progressively with vitellus and secrete a chorion. Before each oviposition degenerative phenomena appears in immature follicles. The ovaries remain at a less developed stage during the 10 days of maternal eggs cares. The follicles at the base of each ovariole degenerate. The cerebral neurosecretory centers and the corpus allatum are active during each vitellogenesis and inactive during each period when follicles degenerate and when the female cares her eggs. An experimental study shows that neurosecretory centers control the activity of the corpus allatum which itself influences the evolution of the vitellogenesis.

  20. Insolation cycles as a major control of equatorial indian ocean primary production

    PubMed

    Beaufort; Lancelot; Camberlin; Cayre; Vincent; Bassinot; Labeyrie

    1997-11-21

    Analysis of a continuous sedimentary record taken in the Maldives indicates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the equatorial Indian Ocean during the past 910,000 years. The record of primary production is coherent and in phase with the February equatorial insolation, whereas it shows diverse phase behavior with delta18O, depending on the orbital frequency (eccentricity, obliquity, or precession) examined. These observations imply a direct control of productivity in the equatorial oceanic system by insolation. In the equatorial Indian Ocean, productivity is driven by the wind intensity of westerlies, which is related to the Southern Oscillation; therefore, it is suggested that a precession forcing on the Southern Oscillation is responsible for the observed paleoproductivity dynamics.

  1. Comparative urban drive cycle simulations of light-duty hybrid vehicles with gasoline or diesel engines and emissions controls

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Smith, David E

    2013-01-01

    Electric hybridization is a very effective approach for reducing fuel consumption in light-duty vehicles. Lean combustion engines (including diesels) have also been shown to be significantly more fuel efficient than stoichiometric gasoline engines. Ideally, the combination of these two technologies would result in even more fuel efficient vehicles. However, one major barrier to achieving this goal is the implementation of lean-exhaust aftertreatment that can meet increasingly stringent emissions regulations without heavily penalizing fuel efficiency. We summarize results from comparative simulations of hybrid electric vehicles with either stoichiometric gasoline or diesel engines that include state-of-the-art aftertreatment emissions controls for both stoichiometric and lean exhaust. Fuel consumption and emissions for comparable gasoline and diesel light-duty hybrid electric vehicles were compared over a standard urban drive cycle and potential benefits for utilizing diesel hybrids were identified. Technical barriers and opportunities for improving the efficiency of diesel hybrids were identified.

  2. A Life-Cycle Cost Estimating Methodology for NASA-Developed Air Traffic Control Decision Support Tools

    NASA Technical Reports Server (NTRS)

    Wang, Jianzhong Jay; Datta, Koushik; Landis, Michael R. (Technical Monitor)

    2002-01-01

    This paper describes the development of a life-cycle cost (LCC) estimating methodology for air traffic control Decision Support Tools (DSTs) under development by the National Aeronautics and Space Administration (NASA), using a combination of parametric, analogy, and expert opinion methods. There is no one standard methodology and technique that is used by NASA or by the Federal Aviation Administration (FAA) for LCC estimation of prospective Decision Support Tools. Some of the frequently used methodologies include bottom-up, analogy, top-down, parametric, expert judgement, and Parkinson's Law. The developed LCC estimating methodology can be visualized as a three-dimensional matrix where the three axes represent coverage, estimation, and timing. This paper focuses on the three characteristics of this methodology that correspond to the three axes.

  3. Application of Ru(bpy) 32+ in control and formation of gold surface nanostructure through oxidation-reduction cycling

    NASA Astrophysics Data System (ADS)

    Bin, Qi; Zheng, Zhikun; Yang, Xiurong

    2007-03-01

    It was studied that the nanostructure formed on a gold surface via a simple oxidation-reduction cycles (ORC) in 0.1 M KCl containing Ru(bpy) 32+ with different concentrations. Atomic force microscopy (AFM) and energy-dispersed spectroscopy (EDS) were used to characterize the nanostructure formed on the gold surface. Sweep-step voltammetry and corresponding electroluminescence (ECL) response, in situ electrochemical quartz crystal microbalance (EQCM) measurement were used to monitor the ORC procedure. It was found that the surface structure became more uniform in the presence of Ru(bpy) 32+, and the surface roughness was decreasing with the increasing of Ru(bpy) 32+ concentration, suggesting a simple and effective method to control the formation of nanostructure on the gold surface.

  4. Waveform-controlled near-single-cycle milli-joule laser pulses generate sub-10 nm extreme ultraviolet continua.

    PubMed

    Schweinberger, Wolfgang; Sommer, Annkatrin; Bothschafter, Elisabeth; Li, Jiang; Krausz, Ferenc; Kienberger, Reinhard; Schultze, Martin

    2012-09-01

    We demonstrate the generation of waveform-controlled laser pulses with 1 mJ pulse energy and a full-width-half-maximum duration of ∼4  fs, therefore lasting less than two cycles of the electric field oscillating at their carrier frequency. The laser source is carrier-envelope-phase stabilized and used as the backbone of a kHz repetition rate source of high-harmonic continua with unprecedented flux at photon energies between 100 and 200 eV (corresponding to a wavelength range between 12-6 nm respectively). In combination we use these tools for the complete temporal characterization of the laser pulses via attosecond streaking spectroscopy.

  5. The carboxy-terminus of p63 links cell cycle control and the proliferative potential of epidermal progenitor cells

    PubMed Central

    Suzuki, Daisuke; Sahu, Raju; Leu, N. Adrian; Senoo, Makoto

    2015-01-01

    The transcription factor p63 (Trp63) plays a key role in homeostasis and regeneration of the skin. The p63 gene is transcribed from dual promoters, generating TAp63 isoforms with growth suppressive functions and dominant-negative ΔNp63 isoforms with opposing properties. p63 also encodes multiple carboxy (C)-terminal variants. Although mutations of C-terminal variants have been linked to the pathogenesis of p63-associated ectodermal disorders, the physiological role of the p63 C-terminus is poorly understood. We report here that deletion of the p63 C-terminus in mice leads to ectodermal malformation and hypoplasia, accompanied by a reduced proliferative capacity of epidermal progenitor cells. Notably, unlike the p63-null condition, we find that p63 C-terminus deficiency promotes expression of the cyclin-dependent kinase inhibitor p21Waf1/Cip1 (Cdkn1a), a factor associated with reduced proliferative capacity of both hematopoietic and neuronal stem cells. These data suggest that the p63 C-terminus plays a key role in the cell cycle progression required to maintain the proliferative potential of stem cells of many different lineages. Mechanistically, we show that loss of Cα, the predominant C-terminal p63 variant in epithelia, promotes the transcriptional activity of TAp63 and also impairs the dominant-negative activity of ΔNp63, thereby controlling p21Waf1/Cip1 expression. We propose that the p63 C-terminus links cell cycle control and the proliferative potential of epidermal progenitor cells via mechanisms that equilibrate TAp63 and ΔNp63 isoform function. PMID:25503409

  6. Hair cycle control by estrogens: catagen induction via estrogen receptor (ER)-alpha is checked by ER beta signaling.

    PubMed

    Ohnemus, Ulrich; Uenalan, Murat; Conrad, Franziska; Handjiski, Bori; Mecklenburg, Lars; Nakamura, Motonobu; Inzunza, José; Gustafsson, Jan-Ake; Paus, Ralf

    2005-03-01

    Although 17beta-estradiol (E2) is recognized as a potent hair growth modulator, our knowledge of estrogen function, signaling, and target genes in hair biology is still very limited. Between the two recognized estrogen receptors (ERs), ER alpha and ER beta, only ER alpha had been detected in murine skin. Here we show that ER alpha, ER beta, and ER beta ins are all expressed throughout the murine hair cycle, both at the protein and RNA level, but show distinct expression patterns. We confirm that topical E2 arrests murine pelage hair follicles in telogen and demonstrate that E2 is a potent inducer of premature catagen development. The ER antagonist ICI 182.780 does not induce anagen prematurely but accelerates anagen development and wave spreading in female mice. ER beta knockout mice display accelerated catagen development along with an increase in the number of apoptotic hair follicle keratinocytes. This suggests that, contrary to previous concepts, ER beta does indeed play a significant role in murine hair growth control: whereas the catagen-promoting properties of E2 are mediated via ER alpha, ER beta mainly may function as a silencer of ER alpha action in hair biology. These findings illustrate the complexity of hair growth modulation by estrogens and suggest that one key to more effective hair growth manipulation with ER ligands lies in the use of selective ER alpha or -beta antagonists/agonists. Our study also underscores that the hair cycling response to estrogens offers an ideal model for studying the controls and dynamics of wave propagation in biological systems.

  7. Inhibition of cullin RING ligases by cycle inhibiting factor: evidence for interference with Nedd8-induced conformational control.

    PubMed

    Boh, Boon Kim; Ng, Mei Ying; Leck, Yee Chin; Shaw, Barry; Long, Jed; Sun, Guang Wen; Gan, Yunn Hwen; Searle, Mark S; Layfield, Robert; Hagen, Thilo

    2011-10-21

    Cycle inhibiting factor (Cif) is produced by pathogenic intracellular bacteria and injected into the host cells via a type III secretion system. Cif is known to interfere with the eukaryotic cell cycle by inhibiting the function of cullin RING E3 ubiquitin ligases (CRLs). Cullin proteins form the scaffold protein of CRLs and are modified with the ubiquitin-like protein Nedd8, which exerts important conformational control required for CRL activity. Cif has recently been shown to catalyze the deamidation of Gln40 in Nedd8 to Glu. Here, we addressed how Nedd8 deamidation inhibits CRL activity. Our results indicate that Burkholderia pseudomallei Cif (also known as CHBP) inhibits the deconjugation of Nedd8 in vivo by inhibiting binding of the deneddylating COP9 signalosome (CSN) complex. We provide evidence that the reduced binding of CSN and the inhibition of CRL activity by Cif are due to interference with Nedd8-induced conformational control, which is dependent on the interaction between the Nedd8 hydrophobic patch and the cullin winged-helix B subdomain. Of note, mutation of Gln40 to Glu in ubiquitin, an additional target of Cif, inhibits the interaction between the hydrophobic surface of ubiquitin and the ubiquitin-binding protein p62/SQSTM1, showing conceptually that Cif activity can impair ubiquitin/ubiquitin-like protein non-covalent interactions. Our results also suggest that Cif may exert additional cellular effects by interfering with the association between ubiquitin and ubiquitin-binding proteins. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Changes in Circulating Levels and Ratios of Angiopoietins during Pregnancy, but not during the Menstrual Cycle and Controlled Ovarian Stimulation

    PubMed Central

    Hurliman, Amanda K.; Speroff, Leon; Stouffer, Richard L.; Patton, Phillip E.; Lee, Annette; Molskness, Theodore A.

    2009-01-01

    OBJECTIVE This study was designed to determine if angiopoietin (ANGPT)-1 and -2 are detectable in