Science.gov

Sample records for cycle alternative mechanisms

  1. Cell cycle arrest and apoptosis, two alternative mechanisms for PMKT2 killer activity.

    PubMed

    Santos, Antonio; Alonso, Alejandro; Belda, Ignacio; Marquina, Domingo

    2013-01-01

    Pichia membranifaciens CYC 1086 secretes a unique 30kDa killer toxin (PMKT2) that inhibits a variety of spoilage yeasts and fungi of agronomical interest. The cytocidal effect of PMKT2 on Saccharomyces cerevisiae cells was studied. Metabolic events associated with the loss of S. cerevisiae viability caused by PMKT2 were qualitatively identical to those reported for K28 killer toxin activity, but different to those reported for PMKT. At higher doses, none of the cellular events accounting for the action of PMKT, the killer toxin secreted by P. membranifaciens CYC 1106, was observed for PMKT2. Potassium leakage, sodium influx and the decrease of intracellular pH were not among the primary effects of PMKT2. We report here that this protein is unable to form ion-permeable channels in liposome membranes, suggesting that channel formation is not the mechanism of cytotoxic action of PMKT2. Nevertheless, flow cytometry studies have revealed a cell cycle arrest at an early S-phase with an immature bud and pre-replicated 1n DNA content. By testing the sensitivity of cells arrested at different stages in the cell cycle, we hoped to identify the execution point for lethality more precisely. Cells arrested at the G1-phase by α-factor or arrested at G2-phase by the spindle poison methyl benzimidazol-2-yl-carbamate (MBC) were protected against the toxin. Cells released from the arrest in both cases were killed by PMKT2 at a similar rate. Nevertheless, cells released from MBC-arrest were able to grow for a short time, and then viability dropped rapidly. These findings suggest that cells released from G2-phase are initially able to divide, but die in the presence of PMKT2 after initiating the S-phase in a new cycle, adopting a terminal phenotype within that cycle. By contrast, low doses of PMKT and PMKT2 were able to generate the same cellular response. The evidence presented here shows that treating yeast with low doses of PMKT2 leads to the typical membranous, cytoplasmic

  2. Separations Needs for the Alternate Chemical Cycles

    SciTech Connect

    Frederick F. Stewart

    2007-05-01

    The bulk of the efforts for the development of a hydrogen production plant supported by the Nuclear Hydrogen Initiative (NHI) have been directed towards the sulfur-iodine (S-I) thermochemical cycle. However, it was judged prudent to re-investigate alternate chemical cycles in light of new developments and technical accomplishments derived from the current S-I work. This work analyzes the available data for the promising alternate chemical cycles to provide an understanding of their inherent chemical separations needs. None of the cycles analyzed have separations that are potential “show stoppers”; although some of the indicated separations will be challenging to perform. The majority of the separations involve processes that are either more achievable or more developed

  3. LIFE CYCLE ASSESSMENT OF ELECTRICITY GENERATION ALTERNATIVES

    EPA Science Inventory

    This presentation summarizes various electricity and electricity/steam cogeneration alternatives. Among these alternatives, are fossil fuel and biomass power generation plants. These plants have different designs due to the need in fossil fuel (coal) plants to include process u...

  4. Alternate thermochemical cycles for advanced hydrogen production

    SciTech Connect

    Bowman, M.G.; Hollabaugh, C.M.; Jones, W.M.; Mason, C.F.V.

    1982-01-01

    Experimental studies have validated three classes of thermochemical cycles (Bismuth sulfate-sulfuric acid, magnesium sulfate-magnesium iodide, and oxide-based) based on high temperature solids decomposition as an endothermic step. Such cycles offer the possibility of high efficiency when coupled with high temperature isothermal heat sources. Methods for handling solids in high temperature decomposition reactions have been tested. The results suggest that efficient and practical cycles can be based on such reactions.

  5. Mechanisms and consequences of alternative polyadenylation

    PubMed Central

    Di Giammartino, Dafne Campigli; Nishida, Kensei; Manley, James L.

    2011-01-01

    Summary Alternative polyadenylation (APA) is emerging as a widespread mechanism used to control gene expression. Like alternative splicing, usage of alternative poly(A) sites allows a single gene to encode multiple mRNA transcripts. In some cases, this changes the mRNA coding potential; in other cases, the code remains unchanged but the 3’UTR length is altered, influencing the fate of mRNAs in several ways, for example, by altering the availability of RNA binding protein sites and microRNA binding sites. The mechansims governing both global and gene-specific APA are only starting to be deciphered. Here we review what is known about these mechanisms and the functional consequences of alternative polyadenlyation. PMID:21925375

  6. Chronically Alternating Light Cycles Increase Breast Cancer Risk in Mice.

    PubMed

    Van Dycke, Kirsten C G; Rodenburg, Wendy; van Oostrom, Conny T M; van Kerkhof, Linda W M; Pennings, Jeroen L A; Roenneberg, Till; van Steeg, Harry; van der Horst, Gijsbertus T J

    2015-07-20

    Although epidemiological studies in shift workers and flight attendants have associated chronic circadian rhythm disturbance (CRD) with increased breast cancer risk, causal evidence for this association is lacking. Several scenarios have been proposed to contribute to the shift work-cancer connection: (1) internal desynchronization, (2) light at night (resulting in melatonin suppression), (3) sleep disruption, (4) lifestyle disturbances, and (5) decreased vitamin D levels due to lack of sunlight. The confounders inherent in human field studies are less problematic in animal studies, which are therefore a good approach to assess the causal relation between circadian disturbance and cancer. However, the experimental conditions of many of these animal studies were far from the reality of human shift workers. For example, some involved xenografts (addressing tumor growth rather than cancer initiation and/or progression), chemically induced tumor models, or continuous bright light exposure, which can lead to suppression of circadian rhythmicity. Here, we have exposed breast cancer-prone p53(R270H/+)WAPCre conditional mutant mice (in a FVB genetic background) to chronic CRD by subjecting them to a weekly alternating light-dark (LD) cycle throughout their life. Animals exposed to the weekly LD inversions showed a decrease in tumor suppression. In addition, these animals showed an increase in body weight. Importantly, this study provides the first experimental proof that CRD increases breast cancer development. Finally, our data suggest internal desynchronization and sleep disturbance as mechanisms linking shift work with cancer development and obesity. PMID:26196479

  7. Life cycle models of conventional and alternative-fueled automobiles

    NASA Astrophysics Data System (ADS)

    Maclean, Heather Louise

    This thesis reports life cycle inventories of internal combustion engine automobiles with feasible near term fuel/engine combinations. These combinations include unleaded gasoline, California Phase 2 Reformulated Gasoline, alcohol and gasoline blends (85 percent methanol or ethanol combined with 15 percent gasoline), and compressed natural gas in spark ignition direct and indirect injection engines. Additionally, I consider neat methanol and neat ethanol in spark ignition direct injection engines and diesel fuel in compression ignition direct and indirect injection engines. I investigate the potential of the above options to have a lower environmental impact than conventional gasoline-fueled automobiles, while still retaining comparable pricing and consumer benefits. More broadly, the objective is to assess whether the use of any of the alternative systems will help to lead to the goal of a more sustainable personal transportation system. The principal tool is the Economic Input-Output Life Cycle Analysis model which includes inventories of economic data, environmental discharges, and resource use. I develop a life cycle assessment framework to assemble the array of data generated by the model into three aggregate assessment parameters; economics, externalities, and vehicle attributes. The first step is to develop a set of 'comparable cars' with the alternative fuel/engine combinations, based on characteristics of a conventional 1998 gasoline-fueled Ford Taurus sedan, the baseline vehicle for the analyses. I calculate the assessment parameters assuming that these comparable cars can attain the potential thermal efficiencies estimated by experts for each fuel/engine combination. To a first approximation, there are no significant differences in the assessment parameters for the vehicle manufacture, service, fixed costs, and the end-of-life for any of the options. However, there are differences in the vehicle operation life cycle components and the state of technology

  8. An Alternative Mechanism for Accelerated Carbon Sequestration in Concrete

    SciTech Connect

    Haselbach, Liv M.; Thomle, Jonathan N.

    2014-07-01

    The increased rate of carbon dioxide sequestration (carbonation) is desired in many primary and secondary life applications of concrete in order to make the life cycle of concrete structures more carbon neutral. Most carbonation rate studies have focused on concrete exposed to air under various conditions. An alternative mechanism for accelerated carbon sequestration in concrete was investigated in this research based on the pH change of waters in contact with pervious concrete which have been submerged in carbonate laden waters. The results indicate that the concrete exposed to high levels of carbonate species in water may carbonate faster than when exposed to ambient air, and that the rate is higher with higher concentrations. Validation of increased carbon dioxide sequestration was also performed via thermogravimetric analysis (TGA). It is theorized that the proposed alternative mechanism reduces a limiting rate effect of carbon dioxide dissolution in water in the micro pores of the concrete.

  9. Elucidating the mechanisms of double ionization using intense half-cycle, single-cycle, and double half-cycle pulses

    SciTech Connect

    Kamta, G. Lagmago; Starace, Anthony F.

    2003-10-01

    We investigate the interaction of a two-active electron system (Li{sup -}) with intense single-cycle and double half-cycle pulses. The 'intensity' and 'frequency' considered correspond to the 'multiphoton above-barrier regime'. For the single-cycle pulse (SCP), the electric field changes sign once, allowing electron wave packets created during the first half cycle to recollide with the parent ion when driven back by the field. For the double half-cycle pulse (DHP), however, the electric field does not change sign, and electron wave packets created during the first half cycle are not driven back to the parent ion. We find that both single and double ionization are significantly larger for the SCP than for the DHP, thereby elucidating the role of the rescattering mechanism. On the other hand, doubly ionized electrons produced by a half-cycle pulse and a DHP are found to have angular distributions in which one electron is ejected in the direction of the pulse field, and the other in the opposite direction. This clear signature of electron correlations suggests that 'shake-off', 'knockout', and, possibly, 'multiphoton-sharing' processes are alternative contributing mechanisms for double ionization in this regime.

  10. Alternative bisphosphonate targets and mechanisms of action.

    PubMed

    Bukowski, Jack F; Dascher, Christopher C; Das, Hiranmoy

    2005-03-18

    As the number of bisphosphonates continues to increase, they have found widespread use in an increasing number of clinical conditions. Ongoing examination of their targets and mechanisms of action has revealed that this surprisingly diverse class of drugs has effects beyond those first described for osteoclasts. These additional targets include osteoblasts, osteocytes, angiogenesis, and gammadelta T lymphocytes of the human immune system. The immune system effects are specifically targeted to gammadelta T cells and are reminiscent of the effects seen after ingestion of tea beverage. BP effects on such alternate targets may explain not only their antiresorptive effect, but also their effect on bone quality, tumors, and microbes.

  11. Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles

    SciTech Connect

    Lvov, Serguei; Chung, Mike; Fedkin, Mark; Lewis, Michele; Balashov, Victor; Chalkova, Elena; Akinfiev, Nikolay; Stork, Carol; Davis, Thomas; Gadala-Maria, Francis; Stanford, Thomas; Weidner, John; Law, Victor; Prindle, John

    2011-01-06

    Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and

  12. Evaluation of alternative thermochemical cycles-part III further development of the Cu-Cl cycle.

    SciTech Connect

    Lewis, M. A.; Ferrandon, M. S.; Tatterson, D. F.; Mathias, P.; Chemical Sciences and Engineering Division

    2009-01-01

    This is the third in a series of papers on alternative cycle evaluation. Part I described the evaluation methodology. Part II described the down-selection process where the most promising of the nine alternative cycles was determined. The Cu-Cl cycle was selected for further development because it alone meets the four criteria used. The current results indicate that the cycle is chemically viable, feasible with respect to engineering, energy-efficient, and capable of meeting DOE's timeline for an Integrated Laboratory Scale (ILS) demonstration. All of the reactions have been proven and the remaining technical challenges should be met with current technologies. The maximum temperature requirement is around 550 C (823 K), which can be obtained with a variety of heat sources. The lower temperature should mitigate the demands on the materials of construction. This paper, Part III, describes the procedure used to develop the Cu-Cl cycle beyond the relatively simple Level 3 efficiency calculation completed by the universities. The optimization process consisted of (i) updating the thermodynamic database used in the Aspen Plus{reg_sign} simulation, (ii) developing a robust flowsheet and optimizing the energy usage therein, (iii) designing a conceptual process incorporating the Aspen Plus{reg_sign} mass and energy flows, and then (iv) estimating the hydrogen production costs. The results presented here are preliminary because further optimization is ongoing.

  13. A life-cycle comparison of alternative automobile fuels.

    PubMed

    MacLean, H L; Lave, L B; Lankey, R; Joshi, S

    2000-10-01

    We examine the life cycles of gasoline, diesel, compressed natural gas (CNG), and ethanol (C2H5OH)-fueled internal combustion engine (ICE) automobiles. Port and direct injection and spark and compression ignition engines are examined. We investigate diesel fuel from both petroleum and biosources as well as C2H5OH from corn, herbaceous bio-mass, and woody biomass. The baseline vehicle is a gasoline-fueled 1998 Ford Taurus. We optimize the other fuel/powertrain combinations for each specific fuel as a part of making the vehicles comparable to the baseline in terms of range, emissions level, and vehicle lifetime. Life-cycle calculations are done using the economic input-output life-cycle analysis (EIO-LCA) software; fuel cycles and vehicle end-of-life stages are based on published model results. We find that recent advances in gasoline vehicles, the low petroleum price, and the extensive gasoline infrastructure make it difficult for any alternative fuel to become commercially viable. The most attractive alternative fuel is compressed natural gas because it is less expensive than gasoline, has lower regulated pollutant and toxics emissions, produces less greenhouse gas (GHG) emissions, and is available in North America in large quantities. However, the bulk and weight of gas storage cylinders required for the vehicle to attain a range comparable to that of gasoline vehicles necessitates a redesign of the engine and chassis. Additional natural gas transportation and distribution infrastructure is required for large-scale use of natural gas for transportation. Diesel engines are extremely attractive in terms of energy efficiency, but expert judgment is divided on whether these engines will be able to meet strict emissions standards, even with reformulated fuel. The attractiveness of direct injection engines depends on their being able to meet strict emissions standards without losing their greater efficiency. Biofuels offer lower GHG emissions, are sustainable, and

  14. A life-cycle comparison of alternative automobile fuels.

    PubMed

    MacLean, H L; Lave, L B; Lankey, R; Joshi, S

    2000-10-01

    We examine the life cycles of gasoline, diesel, compressed natural gas (CNG), and ethanol (C2H5OH)-fueled internal combustion engine (ICE) automobiles. Port and direct injection and spark and compression ignition engines are examined. We investigate diesel fuel from both petroleum and biosources as well as C2H5OH from corn, herbaceous bio-mass, and woody biomass. The baseline vehicle is a gasoline-fueled 1998 Ford Taurus. We optimize the other fuel/powertrain combinations for each specific fuel as a part of making the vehicles comparable to the baseline in terms of range, emissions level, and vehicle lifetime. Life-cycle calculations are done using the economic input-output life-cycle analysis (EIO-LCA) software; fuel cycles and vehicle end-of-life stages are based on published model results. We find that recent advances in gasoline vehicles, the low petroleum price, and the extensive gasoline infrastructure make it difficult for any alternative fuel to become commercially viable. The most attractive alternative fuel is compressed natural gas because it is less expensive than gasoline, has lower regulated pollutant and toxics emissions, produces less greenhouse gas (GHG) emissions, and is available in North America in large quantities. However, the bulk and weight of gas storage cylinders required for the vehicle to attain a range comparable to that of gasoline vehicles necessitates a redesign of the engine and chassis. Additional natural gas transportation and distribution infrastructure is required for large-scale use of natural gas for transportation. Diesel engines are extremely attractive in terms of energy efficiency, but expert judgment is divided on whether these engines will be able to meet strict emissions standards, even with reformulated fuel. The attractiveness of direct injection engines depends on their being able to meet strict emissions standards without losing their greater efficiency. Biofuels offer lower GHG emissions, are sustainable, and

  15. ALTERNATIVE FLOWSHEETS FOR THE SULFUR-IODINE THERMOCHEMICAL HYDROGEN CYCLE

    SciTech Connect

    BROWN,LC; LENTSCH,RD; BESENBRUCH,GE; SCHULTZ,KR; FUNK,JE

    2003-02-01

    OAK-B135 A hydrogen economy will need significant new sources of hydrogen. Unless large-scale carbon sequestration can be economically implemented, use of hydrogen reduces greenhouse gases only if the hydrogen is produced with non-fossil energy sources. Nuclear energy is one of the limited options available. One of the promising approaches to produce large quantities of hydrogen from nuclear energy efficiently is the Sulfur-Iodine (S-I) thermochemical water-splitting cycle, driven by high temperature heat from a helium Gas-Cooled Reactor. They have completed a study of nuclear-driven thermochemical water-splitting processes. The final task of this study was the development of a flowsheet for a prototype S-I production plant. An important element of this effort was the evaluation of alternative flowsheets and selection of the reference design.

  16. Life-Cycle Analysis of Alternative Aviation Fuels in GREET

    SciTech Connect

    Elgowainy, A.; Han, J.; Wang, M.; Carter, N.; Stratton, R.; Hileman, J.; Malwitz, A.; Balasubramanian, S.

    2012-06-01

    The Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model, developed at Argonne National Laboratory, has been expanded to include well-to-wake (WTWa) analysis of aviation fuels and aircraft. This report documents the key WTWa stages and assumptions for fuels that represent alternatives to petroleum jet fuel. The aviation module in GREET consists of three spreadsheets that present detailed characterizations of well-to-pump and pump-to-wake parameters and WTWa results. By using the expanded GREET version (GREET1_2011), we estimate WTWa results for energy use (total, fossil, and petroleum energy) and greenhouse gas (GHG) emissions (carbon dioxide, methane, and nitrous oxide) for (1) each unit of energy (lower heating value) consumed by the aircraft or(2) each unit of distance traveled/ payload carried by the aircraft. The fuel pathways considered in this analysis include petroleum-based jet fuel from conventional and unconventional sources (i.e., oil sands); Fisher-Tropsch (FT) jet fuel from natural gas, coal, and biomass; bio-jet fuel from fast pyrolysis of cellulosic biomass; and bio-jet fuel from vegetable and algal oils, which falls under the American Society for Testing and Materials category of hydroprocessed esters and fatty acids. For aircraft operation, we considered six passenger aircraft classes and four freight aircraft classes in this analysis. Our analysis revealed that, depending on the feedstock source, the fuel conversion technology, and the allocation or displacement credit methodology applied to co-products, alternative bio-jet fuel pathways have the potential to reduce life-cycle GHG emissions by 55–85 percent compared with conventional (petroleum-based) jet fuel. Although producing FT jet fuel from fossil feedstock sources — such as natural gas and coal — could greatly reduce dependence on crude oil, production from such sources (especially coal) produces greater WTWa GHG emissions compared with petroleum jet

  17. Life-cycle analysis of alternative aviation fuels in GREET

    SciTech Connect

    Elgowainy, A.; Han, J.; Wang, M.; Carter, N.; Stratton, R.; Hileman, J.; Malwitz, A.; Balasubramanian, S.

    2012-07-23

    The Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model, developed at Argonne National Laboratory, has been expanded to include well-to-wake (WTWa) analysis of aviation fuels and aircraft. This report documents the key WTWa stages and assumptions for fuels that represent alternatives to petroleum jet fuel. The aviation module in GREET consists of three spreadsheets that present detailed characterizations of well-to-pump and pump-to-wake parameters and WTWa results. By using the expanded GREET version (GREET1{_}2011), we estimate WTWa results for energy use (total, fossil, and petroleum energy) and greenhouse gas (GHG) emissions (carbon dioxide, methane, and nitrous oxide) for (1) each unit of energy (lower heating value) consumed by the aircraft or (2) each unit of distance traveled/ payload carried by the aircraft. The fuel pathways considered in this analysis include petroleum-based jet fuel from conventional and unconventional sources (i.e., oil sands); Fisher-Tropsch (FT) jet fuel from natural gas, coal, and biomass; bio-jet fuel from fast pyrolysis of cellulosic biomass; and bio-jet fuel from vegetable and algal oils, which falls under the American Society for Testing and Materials category of hydroprocessed esters and fatty acids. For aircraft operation, we considered six passenger aircraft classes and four freight aircraft classes in this analysis. Our analysis revealed that, depending on the feedstock source, the fuel conversion technology, and the allocation or displacement credit methodology applied to co-products, alternative bio-jet fuel pathways have the potential to reduce life-cycle GHG emissions by 55-85 percent compared with conventional (petroleum-based) jet fuel. Although producing FT jet fuel from fossil feedstock sources - such as natural gas and coal - could greatly reduce dependence on crude oil, production from such sources (especially coal) produces greater WTWa GHG emissions compared with petroleum jet

  18. The Load Dependence of Kinesin's Mechanical Cycle

    NASA Astrophysics Data System (ADS)

    Coppin, Chris M.; Pierce, Daniel W.; Hsu, Long; Vale, Ronald D.

    1997-08-01

    Kinesin is a dimeric motor protein that transports organelles in a stepwise manner toward the plus-end of microtubules by converting the energy of ATP hydrolysis into mechanical work. External forces can influence the behavior of kinesin, and force-velocity curves have shown that the motor will slow down and eventually stall under opposing loads of ≈ 5 pN. Using an in vitro motility assay in conjunction with a high-resolution optical trapping microscope, we have examined the behavior of individual kinesin molecules under two previously unexplored loading regimes: super-stall loads (>5 pN) and forward (plus-end directed) loads. Whereas some theories of kinesin function predict a reversal of directionality under high loads, we found that kinesin does not walk backwards under loads of up to 13 pN, probably because of an irreversible transition in the mechanical cycle. We also found that this cycle can be significantly accelerated by forward loads under a wide range of ATP concentrations. Finally, we noted an increase in kinesin's rate of dissociation from the microtubule with increasing load, which is consistent with a load dependent partitioning between two recently described kinetic pathways: a coordinated-head pathway (which leads to stepping) and an independent-head pathway (which is static).

  19. Prospectives on the risks of alternative fuel cycles.

    PubMed Central

    Johnson, D H; Kastenberg, W E; Griesmeyer, J M

    1981-01-01

    A commentary is provided on the uncertainties in the data and in qualifying the phenomena relating to the risks imposed by the various steps involved in the use of coal, oil, natural gas, hydropower, and nuclear fuels for the generation of electricity. Uncertainties appear to be extremely large for hydropower which exhibits both large scale ecological impacts and the potential for high consequence, moderate frequency events at specific sites. Major risk-related uncertainties with the use of nuclear fuels include those surrounding nuclear weapons proliferation and reactor accident frequencies and consequences. Uncertainties for coal and oil include specification of the damage function of air transported sulfates and the effects of atmospheric CO2 buildup, acid rain, and groundwater contamination from mine water runoff. Compounding these problems is the potential impact of the growing global competition for a diminishing supply of oil. In the studies reviewed herein, the assessed risks of the nuclear fuel cycle are no greater than those of the primary alternatives. Prudence suggests that we do not totally reject any particular option at this time on the basis of health effects alone; similarly, no option is an undisputed choice. PMID:7270773

  20. Prospectives on the risks of alternative fuel cycles.

    PubMed

    Johnson, D H; Kastenberg, W E; Griesmeyer, J M

    1981-09-01

    A commentary is provided on the uncertainties in the data and in qualifying the phenomena relating to the risks imposed by the various steps involved in the use of coal, oil, natural gas, hydropower, and nuclear fuels for the generation of electricity. Uncertainties appear to be extremely large for hydropower which exhibits both large scale ecological impacts and the potential for high consequence, moderate frequency events at specific sites. Major risk-related uncertainties with the use of nuclear fuels include those surrounding nuclear weapons proliferation and reactor accident frequencies and consequences. Uncertainties for coal and oil include specification of the damage function of air transported sulfates and the effects of atmospheric CO2 buildup, acid rain, and groundwater contamination from mine water runoff. Compounding these problems is the potential impact of the growing global competition for a diminishing supply of oil. In the studies reviewed herein, the assessed risks of the nuclear fuel cycle are no greater than those of the primary alternatives. Prudence suggests that we do not totally reject any particular option at this time on the basis of health effects alone; similarly, no option is an undisputed choice.

  1. Mechanisms and Regulation of Alternative Pre-mRNA Splicing

    PubMed Central

    Lee, Yeon

    2015-01-01

    Precursor messenger RNA (pre-mRNA) splicing is a critical step in the posttranscriptional regulation of gene expression, providing significant expansion of the functional proteome of eukaryotic organisms with limited gene numbers. Split eukaryotic genes contain intervening sequences or introns disrupting protein-coding exons, and intron removal occurs by repeated assembly of a large and highly dynamic ribonucleoprotein complex termed the spliceosome, which is composed of five small nuclear ribonucleoprotein particles, U1, U2, U4/U6, and U5. Biochemical studies over the past 10 years have allowed the isolation as well as compositional, functional, and structural analysis of splicing complexes at distinct stages along the spliceosome cycle. The average human gene contains eight exons and seven introns, producing an average of three or more alternatively spliced mRNA isoforms. Recent high-throughput sequencing studies indicate that 100% of human genes produce at least two alternative mRNA isoforms. Mechanisms of alternative splicing include RNA–protein interactions of splicing factors with regulatory sites termed silencers or enhancers, RNA–RNA base-pairing interactions, or chromatin-based effects that can change or determine splicing patterns. Disease-causing mutations can often occur in splice sites near intron borders or in exonic or intronic RNA regulatory silencer or enhancer elements, as well as in genes that encode splicing factors. Together, these studies provide mechanistic insights into how spliceosome assembly, dynamics, and catalysis occur; how alternative splicing is regulated and evolves; and how splicing can be disrupted by cis- and trans-acting mutations leading to disease states. These findings make the spliceosome an attractive new target for small-molecule, antisense, and genome-editing therapeutic interventions. PMID:25784052

  2. Optimization Of The Alternate Cycle In A Membrane Aeration/Filtration Combined Bioreactor

    NASA Astrophysics Data System (ADS)

    Wang, Hongjie; Dong, Wenyi; Yang, Yue; Gan, Guanghua; Li, Weiguang

    2010-11-01

    In this study, a membrane aeration/filtration combined bioreactor (CMBR) was constructed, and the effect of alternate cycle by CMBR on membrane fouling and oxygen utilization efficiency (OUE) was investigated. Results showed that under the condition, when the alternate cycle was 0.75˜3h, the ΔTMP (TMP value of the time when a filtration cycle was over) of CMBR maintained a basically constant value during the 6 days' continuous operation, which implied the CMBR achieved a favorable effect of the membrane fouling relieving. Too short or too long cycle would lead to a gradual increase of ΔTMP. OUE of CMBR increased with the extension of the alternate cycle. Thus, it suggested that the optimal alternate cycle of CMBR should be 3h.

  3. A Comparison Study of Various Nuclear Fuel Cycle Alternatives

    SciTech Connect

    Kwon, Eun-ha; Ko, Won-il

    2007-07-01

    As a nation develops its nuclear strategies, it must consider various aspects of nuclear energy such as sustainability, environmental-friendliness, proliferation-resistance, economics, technologies, and so on. Like all the policy decision, however, a nuclear fuel cycle option can not be superior in all aspects; the nation must identify its top priority and accordingly evaluate all the possible nuclear fuel cycle options. For such a purpose, this paper takes four different fuel cycle options that are likely adopted by the Korean government, considering the current status of nuclear power generation and the 3. Comprehensive Nuclear Energy Promotion Plan (CNEPP) - Once-through Cycle, DUPIC Recycle, Thermal Recycle and GEN-IV Recycle. The paper then evaluates each option in terms of resource utilization and waste generation. The analysis shows that the GEN-IV Recycle appears to be most competitive from these aspects. (authors)

  4. Alternate energy dissipation? Phenolic metabolites and the xanthophyll cycle.

    PubMed

    Close, Dugald C; Beadle, Chris L

    2003-04-01

    The dynamics of phenolic galloylglucoses (di-, tri-, tetra- and penta-galloylglucose), flavonoids (quercitin and quercitin glycosides) and sideroxylonal were compared with that of xanthophyll cycle-dependent energy dissipation during rapid induction of chilling-dependent photo-inhibition. Pre-dawn xanthophyll cycle engagement of seedlings of Eucalyptus nitens transferred from mild nursery conditions to a low temperature controlled environment increased logarithmically during eight days of treatment. Photochemical efficiency and flavonoids decreased after four days of treatment and non-photochemical quenching after two days of treatment. Galloylglucoses and sideroxylonal decreased linearly during treatment. These results demonstrate that rapid changes in foliar phenolic levels are associated with abrupt changes in the plant environment. It is argued that under these growth-chamber conditions, the xanthophyll cycle facilitated dissipation of excess light energy, lessening the requirement for the dissipation of energy or antioxidant activity through phenolic metabolites.

  5. Representing and constructing liquefaction cycle alternatives for FLNG FEED using system entity structure concepts

    NASA Astrophysics Data System (ADS)

    Ha, Sol; Lee, Kyu-Yeul

    2014-09-01

    To support the procedure for determining an optimal liquefaction cycle for FLNG FEED, an ontological modeling method which can automatically generate various alternative liquefaction cycles were carried out in this paper. General rules in combining equipment are extracted from existing onshore liquefaction cycles like C3MR and DMR cycle. A generic relational model which represents whole relations of the plant elements has all these rules, and it is expressed by using the system entity structure (SES), an ontological framework that hierarchically represents the elements of a system and their relationships. By using a process called pruning which reduces the SES to a candidate, various alternative relational models of the liquefaction cycles can be automatically generated. These alternatives were provided by XML-based formats, and they can be used for choosing an optimal liquefaction cycle on the basis of the assessments such as process simulation and reliability analysis

  6. Empirical Research of College Students' Alternative Frameworks of Particle Mechanics

    ERIC Educational Resources Information Center

    Wang, Hongmei

    2010-01-01

    Based on the constructive theory, about 300 college students of grade 05 of the electronic information specialty of Dezhou University are surveyed for their alternative frameworks of particle mechanics in college physics in this article. In the survey, the questionnaires are used to find out college students' alternative frameworks, and the…

  7. Accelerated Thermal Cycling and Failure Mechanisms

    NASA Technical Reports Server (NTRS)

    Ghaffarian, R.

    1999-01-01

    This paper reviews the accelerated thermal cycling test methods that are currently used by industry to characterize the interconnect reliability of commercial-off-the-shelf (COTS) ball grid array (BGA) and chip scale package (CSP) assemblies.

  8. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ....520 Section 1033.520 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.520 Alternative ramped modal... warm it up. Then follow the provisions of 40 CFR part 1065, subpart F for general pre-test...

  9. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ....520 Section 1033.520 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.520 Alternative ramped modal... warm it up. Then follow the provisions of 40 CFR part 1065, subpart F for general pre-test...

  10. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ....520 Section 1033.520 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.520 Alternative ramped modal... warm it up. Then follow the provisions of 40 CFR part 1065, subpart F for general pre-test...

  11. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ....520 Section 1033.520 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.520 Alternative ramped modal... warm it up. Then follow the provisions of 40 CFR part 1065, subpart F for general pre-test...

  12. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ....520 Section 1033.520 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.520 Alternative ramped modal... warm it up. Then follow the provisions of 40 CFR part 1065, subpart F for general pre-test...

  13. Alternative refrigerants and refrigeration cycles for domestic refrigerators

    SciTech Connect

    Sand, J.R.; Rice, C.L.; Vineyard, E.A.

    1992-12-01

    This project initially focused on using nonazeotropic refrigerant mixtures (NARMs) in a two-evaporator refrigerator-freezer design using two stages of liquid refrigerant subcooling. This concept was proposed and tested in 1975. The work suggested that the concept was 20% more efficient than the conventional one-evaporator refrigerator-freezer (RF) design. After considerable planning and system modeling based on using a NARM in a Lorenz-Meutzner (L-M) RF, the program scope was broadened to include investigation of a ``dual-loop`` concept where energy savings result from exploiting the less stringent operating conditions needed to satisfy cooling, of the fresh food section. A steady-state computer model (CYCLE-Z) capable of simulating conventional, dual loop, and L-M refrigeration cycles was developed. This model was used to rank the performance of 20 ozone-safe NARMs in the L-M refrigeration cycle while key system parameters were systematically varied. The results indicated that the steady-state efficiency of the L-M design was up to 25% greater than that of a conventional cycle. This model was also used to calculate the performance of other pure refrigerants relative to that of dichlorodifluoromethane, R-12, in conventional and dual-loop RF designs. Projected efficiency gains for these cycles were more modest, ranging from 0 to 10%. Individual compressor calorimeter tests of nine combinations of evaporator and condenser temperatures usually used to map RF compressor performance were carried out with R-12 and two candidate L-M NARMs in several compressors. Several models of a commercially produced two-evaporator RF were obtained as test units. Two dual-loop RF designs were built and tested as part of this project.

  14. Alternative refrigerants and refrigeration cycles for domestic refrigerators

    NASA Astrophysics Data System (ADS)

    Sand, J. R.; Rice, C. L.; Vineyard, E. A.

    1992-12-01

    This project initially focused on using nonazeotropic refrigerant mixtures (NARM's) in a two-evaporator refrigerator-freezer design using two stages of liquid refrigerant subcooling. This concept was proposed and tested in 1975. The work suggested that the concept was 20% more efficient than the conventional one-evaporator refrigerator-freezer (RF) design. After considerable planning and system modeling based on using a NARM in a Lorenz-Meutzner (L-M) RF, the program scope was broadened to include investigation of a 'dual-loop' concept where energy savings result from exploiting the less stringent operating conditions needed to satisfy cooling of the fresh food section. A steady-state computer model (CYCLE-Z) capable of simulating conventional, dual loop, and L-M refrigeration cycles was developed. This model was used to rank the performance of 20 ozone-safe NARM's in the L-M refrigeration cycle while key system parameters were systematically varied. The results indicated that the steady-state efficiency of the L-M design was up to 25% greater than that of a conventional cycle. This model was also used to calculate the performance of other pure refrigerants relative to that of dichlorodifluoromethane, R-12, in conventional and dual-loop RF designs. Projected efficiency gains for these cycles were more modest, ranging from 0 to 10%. Individual compressor calorimeter tests of nine combinations of evaporator and condenser temperatures usually used to map RF compressor performance were carried out with R-12 and two candidate L-M NARM's in several compressors. Several models of a commercially produced two-evaporator RF were obtained as test units. Two dual-loop RF designs were built and tested as part of this project.

  15. Tests of alternative reductants in the second uranium purification cycle

    SciTech Connect

    Thompson, M.C.

    1980-05-01

    Miniature mixer-settler tests of the second uranium purification cycle show that plutonium cannot be removed by hydroxylamine-hydrazine (NH/sub 2/OH-N/sub 2/H/sub 4/) because the acidity is too high, or by 2,5-di-t-pentylhydroquinone because HNO/sub 3/ oxidizes the hydroquinone. Plutonium can be removed satisfactorily when U(IV)-hydrazine is used as the reductant.

  16. Mechanisms of cycle development in carbonates

    SciTech Connect

    Grotzinger, J.P.; Read, J.F.

    1985-01-01

    Autocyclic models work in most tectonic environments, and are independent of subsidence, eustacy and time. Autocyclicity requires that: progradation occur in response to differential subsidence across platform; progradation proceeds in direction of increasing subsidence; cycles shallow to sea level; cycles not be significantly affected by vadose diagenesis. Autocyclic models fail to adequately explain causes of transgression. As the prograding wedge reaches its limit, it should approach a state of dynamic equilibrium; any advance will be negatively reinforced by slackened sediment production, while an equal retreat will be negatively reinforced by increased production. Allocyclic models rely on external controls of submergence events, which can result in premature arrest of prograding tidal flats, and incomplete shallowing of shelf to sea level. Episodic subsidence generates submergence events, but does not predict vadose alteration of cycle caps, nor can it operate on cratons or passive-margins where most cycles are formed. Tectono-eustacy might occur in all tectonic settings, but fails to generate significant rates of sea-level rise. Glacio-eustatic models explain the data best, favoring: assymmetric oscillations in sea-level with rapid transgressions; sea level falling below platform generating vadose profiles; arrested progradation and incomplete shallowing to sea level; cycle periods between 20,000 and 100,000 years. Oscillation amplitudes generally were less than 10 m, suggesting alpine rather than continental glaciation.

  17. Comprehensive life cycle inventories of alternative wastewater treatment systems.

    PubMed

    Foley, Jeffrey; de Haas, David; Hartley, Ken; Lant, Paul

    2010-03-01

    Over recent decades, the environmental regulations on wastewater treatment plants (WWTP) have trended towards increasingly stringent nutrient removal requirements for the protection of local waterways. However, such regulations typically ignore other environmental impacts that might accompany apparent improvements to the WWTP. This paper quantitatively defines the life cycle inventory of resources consumed and emissions produced in ten different wastewater treatment scenarios (covering six process configurations and nine treatment standards). The inventory results indicate that infrastructure resources, operational energy, direct greenhouse gas (GHG) emissions and chemical consumption generally increase with increasing nitrogen removal, especially at discharge standards of total nitrogen <5 mgN L(-1). Similarly, infrastructure resources and chemical consumption increase sharply with increasing phosphorus removal, but operational energy and direct GHG emissions are largely unaffected. These trends represent a trade-off of negative environmental impacts against improved local receiving water quality. However, increased phosphorus removal in WWTPs also represents an opportunity for increased resource recovery and reuse via biosolids applied to agricultural land. This study highlights that where biosolids displace synthetic fertilisers, a negative environmental trade-off may also occur by increasing the heavy metals discharged to soil. Proper analysis of these positive and negative environmental trade-offs requires further life cycle impact assessment and an inherently subjective weighting of competing environmental costs and benefits. PMID:20022351

  18. Alternative bacteriophage life cycles: the carrier state of Campylobacter jejuni.

    PubMed

    Siringan, Patcharin; Connerton, Phillippa L; Cummings, Nicola J; Connerton, Ian F

    2014-01-01

    Members of the genus Campylobacter are frequently responsible for human enteric disease, often through consumption of contaminated poultry products. Bacteriophages are viruses that have the potential to control pathogenic bacteria, but understanding their complex life cycles is key to their successful exploitation. Treatment of Campylobacter jejuni biofilms with bacteriophages led to the discovery that phages had established a relationship with their hosts typical of the carrier state life cycle (CSLC), where bacteria and bacteriophages remain associated in equilibrium. Significant phenotypic changes include improved aerotolerance under nutrient-limited conditions that would confer an advantage to survive in extra-intestinal environments, but a lack in motility eliminated their ability to colonize chickens. Under these circumstances, phages can remain associated with a compatible host and continue to produce free virions to prospect for new hosts. Moreover, we demonstrate that CSLC host bacteria can act as expendable vehicles for the delivery of bacteriophages to new host bacteria within pre-colonized chickens. The CSLC represents an important phase in the ecology of Campylobacter bacteriophage. PMID:24671947

  19. Alternative bacteriophage life cycles: the carrier state of Campylobacter jejuni.

    PubMed

    Siringan, Patcharin; Connerton, Phillippa L; Cummings, Nicola J; Connerton, Ian F

    2014-01-01

    Members of the genus Campylobacter are frequently responsible for human enteric disease, often through consumption of contaminated poultry products. Bacteriophages are viruses that have the potential to control pathogenic bacteria, but understanding their complex life cycles is key to their successful exploitation. Treatment of Campylobacter jejuni biofilms with bacteriophages led to the discovery that phages had established a relationship with their hosts typical of the carrier state life cycle (CSLC), where bacteria and bacteriophages remain associated in equilibrium. Significant phenotypic changes include improved aerotolerance under nutrient-limited conditions that would confer an advantage to survive in extra-intestinal environments, but a lack in motility eliminated their ability to colonize chickens. Under these circumstances, phages can remain associated with a compatible host and continue to produce free virions to prospect for new hosts. Moreover, we demonstrate that CSLC host bacteria can act as expendable vehicles for the delivery of bacteriophages to new host bacteria within pre-colonized chickens. The CSLC represents an important phase in the ecology of Campylobacter bacteriophage.

  20. ENVIRONMENTAL LIFE CYCLE ASSESSMENT OF GASOLINE ALTERNATIVES: MTBE AND ETHANOL ADDITIVES

    EPA Science Inventory

    Currently, the U.S. is considering options for additives to reformulated gasoline. To inform this debate the U.S. EPA's Office of Research and Development is conducting a screening life cycle assessment (LCA) of three gasoline alternatives. These alternatives include gasoline w...

  1. Exactly Solvable Quantum Mechanical Potentials: An Alternative Approach.

    ERIC Educational Resources Information Center

    Pronchik, Jeremy N.; Williams, Brian W.

    2003-01-01

    Describes an alternative approach to finding exactly solvable, one-dimensional quantum mechanical potentials. Differs from the usual approach in that instead of starting with a particular potential and seeking solutions to the related Schrodinger equations, it begins with known solutions to second-order ordinary differential equations and seeks to…

  2. An alternative mechanism for guanidinoacetic acid to affect methylation cycle.

    PubMed

    Ostojic, Sergej M

    2014-12-01

    Guanidinoacetic acid (also known as glycocyamine; GAA) is an endogenous substance which occurs in humans and plays a central role in the biosynthesis of creatine. The formation of creatine from GAA consumes methyl groups, and increases production of homocysteine. GAA may have the potential to stimulate insulin secretion. Insulin reduces plasma homocysteine and raises methyl group supply. It is possible that the ability of GAA to trigger the insulin secretion modulates methyl group metabolism, and comparatively counterbalance for the direct effect of GAA on increased methylation demand. Possible insulinotropic effect of GAA may contribute to total in vivo methylation demand during biotransformation. PMID:25468046

  3. The relation between the duty cycle and anesthetic effect in lidocaine iontophoresis using alternating current.

    PubMed

    Wakita, Ryo; Nakajima, Atsushi; Haida, Yu; Umino, Masahiro; Fukayama, Haruhisa

    2011-01-01

    We assessed the effect of the duty cycle on the anesthetic effect during lidocaine alternating current (AC) iontophoresis. A solution of 2% lidocaine was delivered to the medial antecubital skin for 20 minutes using AC iontophoresis with a duty cycle of 60%, 70%, or 80%. The von Frey test was then performed to evaluate the anesthetic effect. In the groups treated with a duty cycle of 80% or 70% the touch thresholds (TT) were significantly elevated from 0 minutes to 30 minutes and from 0 minutes to 20 minutes. TT were significantly elevated at 0 minutes in the group treated with a 60% duty cycle. The anesthetic effect was significantly enhanced in a duty cycle-dependent manner.

  4. Survey of alternative gas turbine engine and cycle design. Final report

    SciTech Connect

    Lukas, H.

    1986-02-01

    In the period of the 1940's to 1960's much experimentation was performed in the areas of intercooling, reheat, and recuperation, as well as the use of low-grade fuels in gas turbines. The Electric Power Research Institute (EPRI), in an effort to document past experience which can be used as the basis for current design activities, commissioned a study to document alternate cycles and components used in gas turbine design. The study was performed by obtaining the important technical and operational criteria of the cycles through a literature search of published documents, articles, and papers. Where possible the information was augmented through dialogue with persons associated with those cycles and with the manufacturers. The survey indicated that many different variations of the simple open-cycle gas turbine plant were used. Many of these changes resulted in increases in efficiency over the low simple-cycle efficiency of that period. Metallurgy, as well as compressor and turbine design, limited the simple-cycle efficiency to the upper teens. The cycle modifications increased those efficiencies to the twenties and thirties. Advances in metallurgy as well as compressor and turbine design, coupled with the decrease in flue cost, stopped the development of these complex cycles. Many of the plants operated successfully for many years, and only because newer simple-cycle gas turbine plants and large steam plants had better heat rates were these units shutdown or put into stand-by service. 24 refs., 25 figs., 114 tabs.

  5. Alternative life cycle strategies of Megalodiscus temperatus in tadpoles and metamorphosed anurans.

    PubMed

    Bolek, M G; Janovy, J

    2008-09-01

    Megalodiscus temperatus (Stafford, 1905) is a common paramphistome trematode of North American amphibians with a two host life cycle and has been reported to infect frogs and rarely tadpoles. In this study we document the alternative life cycle strategy of M. temperatus in tadpoles and metamorphosed anurans. We show through field work and experimental infections that M. temperatus can establish in both anuran life stages and worms become gravid and release eggs in both tadpoles and metamorphosed frogs. However, worms exhibit differences in route of infection, development, egg production, and diet in tadpoles and metamorphosed anurans. These alternative life history strategies of M. temperatus suggest different selective pressures on the development and reproductive success of these worms in tadpoles and metamorphosed anurans, and we discuss the evolutionary avenues for and constraints on amphibian trematode life cycles presented by these two different anuran life stages.

  6. Spacetime alternatives in the quantum mechanics of a relativistic particle

    SciTech Connect

    Whelan, J.T. Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, Cambridge, CB3 0EH )

    1994-11-15

    Hartle's generalized quantum mechanics formalism is used to examine spacetime coarse grainings, i.e., sets of alternatives defined with respect to a region extended in time as well as space, in the quantum mechanics of a free relativistic particle. For a simple coarse graining and suitable initial conditions, tractable formulas are found for branch wave functions. Despite the nonlocality of the positive-definite version of the Klein-Gordon inner product, which means that nonoverlapping branches are not sufficient to imply decoherence, some initial conditions are found to give decoherence and allow the consistent assignment of probabilities.

  7. Dynamic performance of dissipative dielectric elastomers under alternating mechanical load

    NASA Astrophysics Data System (ADS)

    Zhang, Junshi; Chen, Hualing; Sheng, Junjie; Liu, Lei; Wang, Yongquan; Jia, Shuhai

    2014-07-01

    This paper presents a theoretical study about the effect of dissipation on the dynamic performance of a dielectric elastomer membrane subject to a combination of mechanical load and voltage. The thermodynamic dissipative model is given and the equation of motion is deduced by a free energy method. It is found that when the applied mechanical load and voltage are static, the membrane may reach a state of equilibrium after the viscoelastic relaxation. When the voltage is static but the mechanical load is sinusoidal, the membrane will resonate at multiple frequencies. The study result indicates that the viscoelasticity can reduce the natural frequency and increase the mean stretch of the dielectric elastomer. After the power source is cut off, the effect of current leakage on dynamic performance under alternating mechanical load is that the natural frequency increases and the mean stretch reduces.

  8. An extensive program of periodic alternative splicing linked to cell cycle progression

    PubMed Central

    Dominguez, Daniel; Tsai, Yi-Hsuan; Weatheritt, Robert; Wang, Yang; Blencowe, Benjamin J; Wang, Zefeng

    2016-01-01

    Progression through the mitotic cell cycle requires periodic regulation of gene function at the levels of transcription, translation, protein-protein interactions, post-translational modification and degradation. However, the role of alternative splicing (AS) in the temporal control of cell cycle is not well understood. By sequencing the human transcriptome through two continuous cell cycles, we identify ~1300 genes with cell cycle-dependent AS changes. These genes are significantly enriched in functions linked to cell cycle control, yet they do not significantly overlap genes subject to periodic changes in steady-state transcript levels. Many of the periodically spliced genes are controlled by the SR protein kinase CLK1, whose level undergoes cell cycle-dependent fluctuations via an auto-inhibitory circuit. Disruption of CLK1 causes pleiotropic cell cycle defects and loss of proliferation, whereas CLK1 over-expression is associated with various cancers. These results thus reveal a large program of CLK1-regulated periodic AS intimately associated with cell cycle control. DOI: http://dx.doi.org/10.7554/eLife.10288.001 PMID:27015110

  9. Effect of operational cycle time length on nitrogen removal in an alternating oxidation ditch system.

    PubMed

    Mantziaras, I D; Stamou, A; Katsiri, A

    2011-06-01

    This paper refers to nitrogen removal optimization of an alternating oxidation ditch system through the use of a mathematical model and pilot testing. The pilot system where measurements have been made has a total volume of 120 m(3) and consists of two ditches operating in four phases during one cycle and performs carbon oxidation, nitrification, denitrification and settling. The mathematical model consists of one-dimensional mass balance (convection-dispersion) equations based on the IAWPRC ASM 1 model. After the calibration and verification of the model, simulation system performance was made. Optimization is achieved by testing operational cycles and phases with different time lengths. The limits of EU directive 91/271 for nitrogen removal have been used for comparison. The findings show that operational cycles with smaller time lengths can achieve higher nitrogen removals and that an "equilibrium" between phase time percentages in the whole cycle, for a given inflow, must be achieved.

  10. Parallel operation of two Brayton-cycle alternators with parasitic speed controllers

    NASA Technical Reports Server (NTRS)

    Perz, D. A.

    1972-01-01

    The experimental paralleling characteristics of two 1200 Hz Brayton-cycle alternators are presented. Since the Brayton power conversion system uses electric speed controllers, the paralleling requirements are somewhat different from those for conventional ground-based systems. Results include the transient effects of synchronizing the two alternators with various phase-angle, voltage, and frequency differences. Based on these results, the effects of synchronizing differences can be defined, and adjustment requirements of the parasitic speed controllers during synchronizing can be established. Data indicate that parasitically loaded alternators are able to parallel over a wide range of synchronizing differences. However, equilibrium could not be reached in extreme cases where alternator load differences were great and, at the same time, the phase-angle error was large (150 deg or more).

  11. 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

  12. Quantitative Financial Analysis of Alternative Energy Efficiency Shareholder Incentive Mechanisms

    SciTech Connect

    Cappers, Peter; Goldman, Charles; Chait, Michele; Edgar, George; Schlegel, Jeff; Shirley, Wayne

    2008-08-03

    Rising energy prices and climate change are central issues in the debate about our nation's energy policy. Many are demanding increased energy efficiency as a way to help reduce greenhouse gas emissions and lower the total cost of electricity and energy services for consumers and businesses. Yet, as the National Action Plan on Energy Efficiency (NAPEE) pointed out, many utilities continue to shy away from seriously expanding their energy efficiency program offerings because they claim there is insufficient profit-motivation, or even a financial disincentive, when compared to supply-side investments. With the recent introduction of Duke Energy's Save-a-Watt incentive mechanism and ongoing discussions about decoupling, regulators and policymakers are now faced with an expanded and diverse landscape of financial incentive mechanisms, Determining the 'right' way forward to promote deep and sustainable demand side resource programs is challenging. Due to the renaissance that energy efficiency is currently experiencing, many want to better understand the tradeoffs in stakeholder benefits between these alternative incentive structures before aggressively embarking on a path for which course corrections can be time-consuming and costly. Using a prototypical Southwest utility and a publicly available financial model, we show how various stakeholders (e.g. shareholders, ratepayers, etc.) are affected by these different types of shareholder incentive mechanisms under varying assumptions about program portfolios. This quantitative analysis compares the financial consequences associated with a wide range of alternative incentive structures. The results will help regulators and policymakers better understand the financial implications of DSR program incentive regulation.

  13. Millimeter wave detection of nuclear radiation: An alternative detection mechanism

    SciTech Connect

    Gopalsami, N.; Chien, H. T.; Heifetz, A.; Koehl, E. R.; Raptis, A. C.

    2009-08-15

    We present a nuclear radiation detection mechanism using millimeter waves as an alternative to conventional detection. It is based on the concept that nuclear radiation causes ionization of air and that if we place a dielectric material near the radiation source, it acts as a charge accumulator of the air ions. We have found that millimeter waves can interrogate the charge cloud on the dielectric material remotely. This concept was tested with a standoff millimeter wave system by monitoring the charge levels on a cardboard tube placed in an x-ray beam.

  14. Millimeter wave detection of nuclear radiation - an alternative detection mechanism.

    SciTech Connect

    Gopalsami, N.; Chien, H. T.; Heifetz, A.; Koehl, E. R.; Raptis, A. C.; Nuclear Engineering Division

    2009-08-01

    We present a nuclear radiation detection mechanism using millimeter waves as an alternative to conventional detection. It is based on the concept that nuclear radiation causes ionization of air and that if we place a dielectric material near the radiation source, it acts as a charge accumulator of the air ions. We have found that millimeter waves can interrogate the charge cloud on the dielectric material remotely. This concept was tested with a standoff millimeter wave system by monitoring the charge levels on a cardboard tube placed in an x-ray beam.

  15. Millimeter wave detection of nuclear radiation: an alternative detection mechanism.

    PubMed

    Gopalsami, N; Chien, H T; Heifetz, A; Koehl, E R; Raptis, A C

    2009-08-01

    We present a nuclear radiation detection mechanism using millimeter waves as an alternative to conventional detection. It is based on the concept that nuclear radiation causes ionization of air and that if we place a dielectric material near the radiation source, it acts as a charge accumulator of the air ions. We have found that millimeter waves can interrogate the charge cloud on the dielectric material remotely. This concept was tested with a standoff millimeter wave system by monitoring the charge levels on a cardboard tube placed in an x-ray beam.

  16. Comparative evaluation of three alternative power cycles for waste heat recovery from the exhaust of adiabatic diesel engines

    NASA Technical Reports Server (NTRS)

    Bailey, M. M.

    1985-01-01

    Three alternative power cycles were compared in application as an exhaust-gas heat-recovery system for use with advanced adiabatic diesel engines. The power cycle alternatives considered were steam Rankine, organic Rankine with RC-1 as the working fluid, and variations of an air Brayton cycle. The comparison was made in terms of fuel economy and economic payback potential for heavy-duty trucks operating in line-haul service. The results indicate that, in terms of engine rated specific fuel consumption, a diesel/alternative-power-cycle engine offers a significant improvement over the turbocompound diesel used as the baseline for comparison. The maximum imporvement resulted from the use of a Rankine cycle heat-recovery system in series with turbocompounding. The air Brayton cycle alternatives studied, which included both simple-cycle and compression-intercooled configurations, were less effective and provided about half the fuel consumption improvement of the Rankine cycle alternatives under the same conditions. Capital and maintenance cost estimates were also developed for each of the heat-recovery power cycle systems. These costs were integrated with the fuel savings to identify the time required for net annual savings to pay back the initial capital investment. The sensitivity of capital payback time to arbitrary increases in fuel price, not accompanied by corresponding hardware cost inflation, was also examined. The results indicate that a fuel price increase is required for the alternative power cycles to pay back capital within an acceptable time period.

  17. Effect of alternative pathway therapy on branched chain amino acid metabolism in urea cycle disorder patients.

    PubMed

    Scaglia, Fernando; Carter, Susan; O'Brien, William E; Lee, Brendan

    2004-04-01

    Urea cycle disorders (UCDs) are a group of inborn errors of hepatic metabolism caused by the loss of enzymatic activities that mediate the transfer of nitrogen from ammonia to urea. These disorders often result in life-threatening hyperammonemia and hyperglutaminemia. A combination of sodium phenylbutyrate and sodium phenylacetate/benzoate is used in the clinical management of children with urea cycle defects as a glutamine trap, diverting nitrogen from urea synthesis to alternatives routes of excretion. We have observed that patients treated with these compounds have selective branched chain amino acid (BCAA) deficiency despite adequate dietary protein intake. However, the direct effect of alternative therapy on the steady state levels of plasma branched chain amino acids has not been well characterized. We have measured steady state plasma branched chain and other essential non-branched chain amino acids in control subjects, untreated ornithine transcarbamylase deficiency females and treated null activity urea cycle disorder patients in the fed steady state during the course of stable isotope studies. Steady-state leucine levels were noted to be significantly lower in treated urea cycle disorder patients when compared to either untreated ornithine transcarbamylase deficiency females or control subjects (P<0.0001). This effect was reproduced in control subjects who had depressed leucine levels when treated with sodium phenylacetate/benzoate (P<0.0001). Our studies suggest that this therapeutic modality has a substantial impact on the metabolism of branched chain amino acids in urea cycle disorder patients. These findings suggest that better titration of protein restriction could be achieved with branched chain amino acid supplementation in patients with UCDs who are on alternative route therapy.

  18. Catalytic and mechanical cycles in F-ATP synthases: Fourth in the Cycles Review Series

    PubMed Central

    Dimroth, Peter; von Ballmoos, Christoph; Meier, T

    2006-01-01

    Cycles have a profound role in cellular life at all levels of organization. Well-known cycles in cell metabolism include the tricarboxylic acid and the urea cycle, in which a specific carrier substrate undergoes a sequence of chemical transformations and is regenerated at the end. Other examples include the interconversions of cofactors, such as NADH or ATP, which are present in the cell in limiting amounts and have to be recycled effectively for metabolism to continue. Every living cell performs a rapid turnover of ATP to ADP to fulfil various energetic demands and effectively regenerates the ATP from ADP in an energy-consuming process. The turnover of the ATP cycle is impressive; a human uses about its body weight in ATP per day. Enzymes perform catalytic reaction cycles in which they undergo several chemical and physical transformations before they are converted back to their original states. The ubiquitous F1Fo ATP synthase is of particular interest not only because of its biological importance, but also owing to its unique rotational mechanism. Here, we give an overview of the membrane-embedded Fo sector, particularly with respect to the recent crystal structure of the c ring from Ilyobacter tartaricus, and summarize current hypotheses for the mechanism by which rotation of the c ring is generated. PMID:16607397

  19. The life cycle assessment of alternative fuel chains for urban buses and trolleybuses.

    PubMed

    Kliucininkas, L; Matulevicius, J; Martuzevicius, D

    2012-05-30

    This paper describes a comparative analysis of public transport alternatives in the city of Kaunas, Lithuania. An LCA (Life Cycle Assessment) inventory analysis of fuel chains was undertaken using the midi urban bus and a similar type of trolleybus. The inventory analysis of fuel chains followed the guidelines provided by the ISO 14040 and ISO 14044 standards. The ReCiPe Life Cycle Impact Assessment (LCIA) methodology was used to quantify weighted damage originating from five alternative fuel chains. The compressed biogas fuel chain had the lowest weighted damage value, namely 45.7 mPt/km, whereas weighted damage values of the fuel chains based on electricity generation for trolleybuses were 60.6 mPt/km (for natural gas) and 78.9 mPt/km (for heavy fuel oil). The diesel and compressed natural gas fuel chains exhibited considerably higher damage values of 114.2 mPt/km and 132.6 mPt/km, respectively. The comparative life cycle assessment of fuel chains suggested that biogas-powered buses and electric trolleybuses can be considered as the best alternatives to use when modernizing the public transport fleet in Kaunas. PMID:22326758

  20. The life cycle assessment of alternative fuel chains for urban buses and trolleybuses.

    PubMed

    Kliucininkas, L; Matulevicius, J; Martuzevicius, D

    2012-05-30

    This paper describes a comparative analysis of public transport alternatives in the city of Kaunas, Lithuania. An LCA (Life Cycle Assessment) inventory analysis of fuel chains was undertaken using the midi urban bus and a similar type of trolleybus. The inventory analysis of fuel chains followed the guidelines provided by the ISO 14040 and ISO 14044 standards. The ReCiPe Life Cycle Impact Assessment (LCIA) methodology was used to quantify weighted damage originating from five alternative fuel chains. The compressed biogas fuel chain had the lowest weighted damage value, namely 45.7 mPt/km, whereas weighted damage values of the fuel chains based on electricity generation for trolleybuses were 60.6 mPt/km (for natural gas) and 78.9 mPt/km (for heavy fuel oil). The diesel and compressed natural gas fuel chains exhibited considerably higher damage values of 114.2 mPt/km and 132.6 mPt/km, respectively. The comparative life cycle assessment of fuel chains suggested that biogas-powered buses and electric trolleybuses can be considered as the best alternatives to use when modernizing the public transport fleet in Kaunas.

  1. Changes of alternative respiration during the division cycle of Candida tropicalis.

    PubMed

    Novák, B; László, E

    1988-01-01

    The changes in cyanide-resistant and SHAM-sensitive respiration have been examined in the cell cycle of yeast cells synchronized by nutrient starvation. The changing of the cyanide-resistant respiration of cells proliferating in synchronizing fermentor, where the glucose concentration was continuously decreasing, was associated with the stage in cell cycle rather than with the alteration of environment. The cyanide-resistant alternative respiration may be attributed characteristic of a certain part of the cell cycle termed "A" phase. This hypothesis is supported by the observation that in cultures proliferating, synchronously under constant conditions, the cyanide-resistant respiration changes periodically and reaches its maximum in the "A" phase after the cell division.

  2. Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms

    PubMed Central

    Antal, Andrea; Herrmann, Christoph S.

    2016-01-01

    Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS. Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions. Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations. Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations. PMID:27242932

  3. Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms.

    PubMed

    Antal, Andrea; Herrmann, Christoph S

    2016-01-01

    Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS. Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions. Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations. Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations. PMID:27242932

  4. Management of radioactive waste gases from the nuclear fuel cycle. Volume I. Comparison of alternatives

    SciTech Connect

    Evans, A.G.; Prout, W.E.; Buckner, J.T.; Buckner, M.R.

    1980-12-01

    Alternatives were compared for collection and fixation of radioactive waste gases released during normal operation of the nuclear fuel cycle, and for transportation and storage/disposal of the resulting waste forms. The study used a numerical rating scheme to evaluate and compare the alternatives for krypton-85, iodine-129, and carbon-14; whereas a subjective evaluation, based on published reports and engineering judgement, was made for transportation and storage/disposal options. Based on these evaluations, certain alternatives are recommended for an integrated scheme for waste management of each of the subject waste gases. Phase II of this project, which is concerned with the development of performance criteria for the waste forms associated with the subject gases, will be completed by the end of 1980. This work will be documented as Volume II of this report.

  5. A simple calibration method for mechanically braked cycle ergometers.

    PubMed

    Van Praagh, E; Bedu, M; Roddier, P; Coudert, J

    1992-01-01

    The calibration of cycle ergometers should be checked regularly. Some studies have shown calibration errors of more than 40%. A simple, inexpensive calibrating method for mechanically braked cycle ergometers was developed and tried out on a new type of ergocycle. The cycle ergometer was elevated and the crank replaced by a pulley fitted to the shaft. The crank speed (rpm) increased linearly as a function of time when different masses were applied on the pulley. For a given braking force on the cycle ergometer, different accelerations corresponding to the increased pulley forces could be measured. When extrapolating for zero acceleration, it was possible to determine a "limit-force" which allowed the system to be in equilibrium. Additional force creates motion. The same experiments were repeated with increasing braking forces. Using the differently sized gear sprockets of the transmission system, it was possible to calculate the actual force, including all the resistances. The actual force found by the calibrating method was then compared with the indicated force proposed by the manufacturer. With increasing forces, the relative errors decreased from 9.6 to 2.9%. The cycle ergometer calibrated by this technique meets the standards recommended in exercise physiology. PMID:1544728

  6. Epigenetic mechanisms in diurnal cycles of metabolism and neurodevelopment.

    PubMed

    Powell, Weston T; LaSalle, Janine M

    2015-10-15

    The circadian cycle is a genetically encoded clock that drives cellular rhythms of transcription, translation and metabolism. The circadian clock interacts with the diurnal environment that also drives transcription and metabolism during light/dark, sleep/wake, hot/cold and feast/fast daily and seasonal cycles. Epigenetic regulation provides a mechanism for cells to integrate genetic programs with environmental signals in order produce an adaptive and consistent output. Recent studies have revealed that DNA methylation is one epigenetic mechanism that entrains the circadian clock to a diurnal environment. We also review recent circadian findings in the epigenetic neurodevelopmental disorders Prader-Willi, Angelman and Rett syndromes and hypothesize a link between optimal brain development and intact synchrony between circadian and diurnal rhythms. PMID:26105183

  7. Fuel-cycle greenhouse gas emissions impacts of alternative transportation fuels and advanced vehicle technologies.

    SciTech Connect

    Wang, M. Q.

    1998-12-16

    At an international conference on global warming, held in Kyoto, Japan, in December 1997, the United States committed to reduce its greenhouse gas (GHG) emissions by 7% over its 1990 level by the year 2012. To help achieve that goal, transportation GHG emissions need to be reduced. Using Argonne's fuel-cycle model, I estimated GHG emissions reduction potentials of various near- and long-term transportation technologies. The estimated per-mile GHG emissions results show that alternative transportation fuels and advanced vehicle technologies can help significantly reduce transportation GHG emissions. Of the near-term technologies evaluated in this study, electric vehicles; hybrid electric vehicles; compression-ignition, direct-injection vehicles; and E85 flexible fuel vehicles can reduce fuel-cycle GHG emissions by more than 25%, on the fuel-cycle basis. Electric vehicles powered by electricity generated primarily from nuclear and renewable sources can reduce GHG emissions by 80%. Other alternative fuels, such as compressed natural gas and liquefied petroleum gas, offer limited, but positive, GHG emission reduction benefits. Among the long-term technologies evaluated in this study, conventional spark ignition and compression ignition engines powered by alternative fuels and gasoline- and diesel-powered advanced vehicles can reduce GHG emissions by 10% to 30%. Ethanol dedicated vehicles, electric vehicles, hybrid electric vehicles, and fuel-cell vehicles can reduce GHG emissions by over 40%. Spark ignition engines and fuel-cell vehicles powered by cellulosic ethanol and solar hydrogen (for fuel-cell vehicles only) can reduce GHG emissions by over 80%. In conclusion, both near- and long-term alternative fuels and advanced transportation technologies can play a role in reducing the United States GHG emissions.

  8. Alternative life cycle strategies and colonization of young anurans by Gorgoderina attenuata in Nebraska.

    PubMed

    Bolek, Matthew G; Snyder, Scott D; Janovy, John

    2009-06-01

    Studies on life cycles and epizootiology of North American frog bladder flukes indicate that adult frogs become infected predominantly by ingesting tadpoles or other frogs that serve as second intermediate hosts for gorgoderid metacercariae. Other studies have indicated that newly metamorphosed frogs are rarely infected with these parasites because they are gape-limited predators that cannot feed on large intermediate hosts such as tadpoles and other frogs. We examined the role of potential intermediate hosts in the recruitment of the frog bladder fluke, Gorgoderina attenuata, to metamorphosed northern leopard frogs, Woodhouse's toads, and bullfrogs from western Nebraska. We completed the life cycle of G. attenuata in the laboratory in 3 anuran species by experimentally infecting a variety of hosts. In addition, we generated and compared DNA sequence data from life cycle stages collected from a variety of naturally infected hosts. Our field and laboratory data indicate that in Nebraska G. attenuata has a truncated, 2-host life cycle that includes fingernail clams and anurans. Cercariae are ingested directly by tadpoles; unencysted juvenile worms then develop in the kidneys of tadpoles before moving to, and maturing in, the urinary bladder when tadpoles metamorphose. Additionally, G. attenuata can infect metamorphosed leopard frogs, bullfrogs, and toads when metacercariae in damselfly second intermediate hosts are ingested. These worms can also infect adult bullfrogs when they feed on other infected anurans possessing worms in their kidneys. Comparison of our material to published accounts of G. attenuata morphology and life cycles in Massachusetts suggests that previous work may have inadvertently involved 2 different species of gorgoderids. Our comparative approach to life cycle studies in different anuran life stages and multiple species of hosts suggests that tadpoles and metamorphosed anurans have favored alternative life cycle strategies in this trematode

  9. Alternative life cycle strategies and colonization of young anurans by Gorgoderina attenuata in Nebraska.

    PubMed

    Bolek, Matthew G; Snyder, Scott D; Janovy, John

    2009-06-01

    Studies on life cycles and epizootiology of North American frog bladder flukes indicate that adult frogs become infected predominantly by ingesting tadpoles or other frogs that serve as second intermediate hosts for gorgoderid metacercariae. Other studies have indicated that newly metamorphosed frogs are rarely infected with these parasites because they are gape-limited predators that cannot feed on large intermediate hosts such as tadpoles and other frogs. We examined the role of potential intermediate hosts in the recruitment of the frog bladder fluke, Gorgoderina attenuata, to metamorphosed northern leopard frogs, Woodhouse's toads, and bullfrogs from western Nebraska. We completed the life cycle of G. attenuata in the laboratory in 3 anuran species by experimentally infecting a variety of hosts. In addition, we generated and compared DNA sequence data from life cycle stages collected from a variety of naturally infected hosts. Our field and laboratory data indicate that in Nebraska G. attenuata has a truncated, 2-host life cycle that includes fingernail clams and anurans. Cercariae are ingested directly by tadpoles; unencysted juvenile worms then develop in the kidneys of tadpoles before moving to, and maturing in, the urinary bladder when tadpoles metamorphose. Additionally, G. attenuata can infect metamorphosed leopard frogs, bullfrogs, and toads when metacercariae in damselfly second intermediate hosts are ingested. These worms can also infect adult bullfrogs when they feed on other infected anurans possessing worms in their kidneys. Comparison of our material to published accounts of G. attenuata morphology and life cycles in Massachusetts suggests that previous work may have inadvertently involved 2 different species of gorgoderids. Our comparative approach to life cycle studies in different anuran life stages and multiple species of hosts suggests that tadpoles and metamorphosed anurans have favored alternative life cycle strategies in this trematode.

  10. Assessment of Alternative Funding Mechanisms for the IAEA

    SciTech Connect

    Toomey, Christopher; Wyse, Evan T.; Kurzrok, Andrew J.; Ford, Benjamin E.

    2012-06-15

    While the International Atomic Energy Agency (IAEA) has enjoyed substantial success and prestige in the international community, there is growing concern that global demographic trends, advances in technology and the trend towards austerity in Member State budgets will stretch the Agency’s resources to a point where it may no longer be possible to execute its multifaceted mission in its entirety. As part of an ongoing effort by the Next Generation Safeguards Initiative to evaluate the IAEA’s long-term budgetary concerns , this paper proposes a series of alternate funding mechanisms that have the potential to sustain the IAEA in the long-term, including endowment, charity, and fee-for-service funding models.

  11. Effect of "Pose" cycling on efficiency and pedaling mechanics.

    PubMed

    Korff, Thomas; Fletcher, Graham; Brown, David; Romer, Lee M

    2011-06-01

    The purpose of this study was to determine the effect of "Pose" cycling (a combination of specific bicycle setup and pedaling technique) on metabolic efficiency and pedaling mechanics. Eighteen recreational cyclists were tested for efficiency and pedaling mechanics during steady-state cycling (90% gas-exchange threshold) using two different bicycle setups (preferred and "Pose") and three different pedaling rates (70, 90 and 110 rpm). Nine of the participants underwent a coaching intervention (4 × 1 h) consisting of drills based on the "Pose" instruction manual. The remaining nine participants did not receive an intervention. All participants were tested before and after the intervention period. Analyses of variance were performed to test the independent effects of the "Pose"-specific bicycle setup and pedaling technique on gross efficiency and pedaling mechanics. The "Pose"-specific bicycle setup resulted in increased gross efficiency at each pedaling rate compared to the participants' preferred bicycle position (P < 0.05). This increase in efficiency was accompanied by a significant increase in trunk frontal area (P < 0.05). The coaching intervention resulted in decreased gross efficiency at 110 rpm (P < 0.05); at this pedaling rate the intervention resulted in a slight increase in the non-muscular contribution to pedal power in the experimental group and a decrease in the control group. The combination of changed bicycle setup and pedaling technique had no effect on gross efficiency and only small effects on pedaling mechanics. Our findings add to a growing body of literature that short-term interventions in pedaling technique can change pedaling mechanics but do not improve efficiency during steady-state cycling.

  12. Alternative development in Polystoma gallieni (Platyhelminthes, Monogenea) and life cycle evolution.

    PubMed

    Badets, Mathieu; Du Preez, Louis; Verneau, Olivier

    2013-10-01

    Considering the addition of intermediate transmission steps during life cycle evolution, developmental plasticity, canalization forces and inherited parental effect must be invoked to explain new host colonization. Unfortunately, there is a lack of experimental procedures and relevant models to explore the adaptive value of alternative developmental phenotypes during life cycle evolution. However, within the monogeneans that are characterized by a direct life cycle, an extension of the transmission strategy of amphibian parasites has been reported within species of Polystoma and Metapolystoma (Polyopisthocotylea; Polystomatidae). In this study, we tested whether the infection success of Polystoma gallieni within tadpoles of its specific host, the Stripeless Tree Frog Hyla meridionalis, differs depending on the parental origin of the oncomiracidium. An increase in the infection success of the parasitic larvae when exposed to the same experimental conditions as their parents was expected as an adaptive pattern of non-genetic inherited information. Twice as many parasites were actually recorded from tadpoles infected with oncomiracidia hatching from eggs of the bladder parental phenotype (1.63 ± 0.82 parasites per host) than from tadpoles infected with oncomiracidia hatching from eggs of the branchial parental phenotype (0.83 ± 0.64 parasites per host). Because in natural environments the alternation of the two phenotypes is likely to occur due to the ecology of its host, the differential infection success within young tadpoles could have an adaptive value that favors the parasite transmission over time.

  13. Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    1998-01-01

    Ceramic thermal barrier coatings have attracted increased attention for diesel engine applications. The advantages of using the ceramic coatings include a potential increase in efficiency and power density and a decrease in maintenance cost. Zirconia-based ceramics are the most important coating materials for such applications because of their low thermal conductivity, relatively high thermal expansivity and excellent mechanical properties. However, durability of thick thermal barrier coatings (TBCS) under severe temperature cycling encountered in engine conditions, remains a major question. The thermal transients associated with the start/stop and no-load/full-load engine cycle, and with the in-cylinder combustion process, generate thermal low cycle fatigue (LCF) and thermal high cycle fatigue (HCF) in the coating system. Therefore, the failure mechanisms of thick TBCs are expected to be quite different from those of thin TBCs under these temperature transients. The coating failure is related not only to thermal expansion mismatch and oxidation of the bond coats and substrates, but also to the steep thermal stress gradients induced in the coating systems. Although it has been reported that stresses generated by thermal transients can initiate surface and interface cracks in a coating system, the mechanisms of the crack propagation and of coating failure under the complex LCF and HCF conditions are still not understood. In this paper, the thermal fatigue behavior of an yttria partially stabilized zirconia coating system under simulated LCF and HCF engine conditions is investigated. The effects of LCF and HCF on surface crack initiation and propagation are also discussed.

  14. Alternative splicing: An important mechanism in stem cell biology

    PubMed Central

    Chen, Kenian; Dai, Xiaojing; Wu, Jiaqian

    2015-01-01

    Alternative splicing (AS) is an essential mechanism in post-transcriptional regulation and leads to protein diversity. It has been shown that AS is prevalent in metazoan genomes, and the splicing pattern is dynamically regulated in different tissues and cell types, including embryonic stem cells. These observations suggest that AS may play critical roles in stem cell biology. Since embryonic stem cells and induced pluripotent stem cells have the ability to give rise to all types of cells and tissues, they hold the promise of future cell-based therapy. Many efforts have been devoted to understanding the mechanisms underlying stem cell self-renewal and differentiation. However, most of the studies focused on the expression of a core set of transcription factors and regulatory RNAs. The role of AS in stem cell differentiation was not clear. Recent advances in high-throughput technologies have allowed the profiling of dynamic splicing patterns and cis-motifs that are responsible for AS at a genome-wide scale, and provided novel insights in a number of studies. In this review, we discuss some recent findings involving AS and stem cells. An emerging picture from these findings is that AS is integrated in the transcriptional and post-transcriptional networks and together they control pluripotency maintenance and differentiation of stem cells. PMID:25621101

  15. Moving toward multilateral mechanisms for the fuel cycle

    SciTech Connect

    Panasyuk,A.; Rosenthal,M.; Efremov, G. V.

    2009-04-17

    Multilateral mechanisms for the fuel cycle are seen as a potentially important way to create an industrial infrastructure that will support a renaissance and at the same time not contribute to the risk of nuclear proliferation. In this way, international nuclear fuel cycle centers for enrichment can help to provide an assurance of supply of nuclear fuel that will reduce the likelihood that individual states will pursue this sensitive technology, which can be used to produce nuclear material directly usable nuclear weapons. Multinational participation in such mechanisms can also potentially promote transparency, build confidence, and make the implementation of IAEA safeguards more effective or more efficient. At the same time, it is important to ensure that there is no dissemination of sensitive technology. The Russian Federation has taken a lead role in this area by establishing an International Uranium Enrichment Center (IUEC) for the provision of enrichment services at its uranium enrichment plant located at the Angarsk Electrolysis Chemical Complex (AECC). This paper describes how the IUEe is organized, who its members are, and the steps that it has taken both to provide an assured supply of nuclear fuel and to ensure protection of sensitive technology. It also describes the relationship between the IUEC and the IAEA and steps that remain to be taken to enhance its assurance of supply. Using the IUEC as a starting point for discussion, the paper also explores more generally the ways in which features of such fuel cycle centers with multinational participation can have an impact on safeguards arrangements, transparency, and confidence-building. Issues include possible lAEA safeguards arrangements or other links to the IAEA that might be established at such fuel cycle centers, impact of location in a nuclear weapon state, and the transition by the IAEA to State Level safeguards approaches.

  16. An alternative mechanism of bioluminescence color determination in firefly luciferase.

    PubMed

    Branchini, Bruce R; Southworth, Tara L; Murtiashaw, Martha H; Magyar, Rachelle A; Gonzalez, Susan A; Ruggiero, Maria C; Stroh, Justin G

    2004-06-15

    Beetle luciferases (including those of the firefly) use the same luciferin substrate to naturally display light ranging in color from green (lambda(max) approximately 530 nm) to red (lambda(max) approximately 635 nm). In a recent communication, we reported (Branchini, B. R., Murtiashaw, M. H., Magyar, R. A., Portier, N. C., Ruggiero, M. C., and Stroh, J. G. (2002) J. Am. Chem. Soc. 124, 2112-2113) that the synthetic adenylate of firefly luciferin analogue D-5,5-dimethylluciferin was transformed into the emitter 5,5-dimethyloxyluciferin in bioluminescence reactions catalyzed by luciferases from Photinus pyralis and the click beetle Pyrophorus plagiophthalamus. 5,5-Dimethyloxyluciferin is constrained to exist in the keto form and fluoresces mainly in the red. However, bioluminescence spectra revealed that green light emission was produced by the firefly enzyme, and red light was observed with the click beetle protein. These results, augmented with steady-state kinetic studies, were taken as experimental support for mechanisms of firefly bioluminescence color that require only a single keto form of oxyluciferin. We report here the results of mutagenesis studies designed to determine the basis of the observed differences in bioluminescence color with the analogue adenylate. Mutants of P. pyralis luciferase putative active site residues Gly246 and Phe250, as well as corresponding click beetle residues Ala243 and Ser247 were constructed and characterized using bioluminescence emission spectroscopy and steady state kinetics with adenylate substrates. Based on an analysis of these and recently reported (Branchini, B. R., Southworth, T. L., Murtiashaw, M. H., Boije, H., and Fleet, S. E. (2003) Biochemistry 42, 10429-10436) data, we have developed an alternative mechanism of bioluminescence color. The basis of the mechanism is that luciferase modulates emission color by controlling the resonance-based charge delocalization of the anionic keto form of the oxyluciferin excited

  17. The Dynamical Mechanisms of the Cell Cycle Size Checkpoint

    NASA Astrophysics Data System (ADS)

    Feng, Shi-Fu; Yan, Jie; Liu, Zeng-Rong; Yang, Ling

    2012-10-01

    Cell division must be tightly coupled to cell growth in order to maintain cell size, whereas the mechanisms of how initialization of mitosis is regulated by cell size remain to be elucidated. We develop a mathematical model of the cell cycle, which incorporates cell growth to investigate the dynamical properties of the size checkpoint in embryos of Xenopus laevis. We show that the size checkpoint is naturally raised from a saddle-node bifurcation, and in a mutant case, the cell loses its size control ability due to the loss of this saddle-node point.

  18. Comparative life-cycle cost analysis for low-level mixed waste remediation alternatives

    SciTech Connect

    Jackson, J.A.; White, T.P.; Kloeber, J.M.; Toland, R.J.; Cain, J.P.; Buitrago, D.Y.

    1995-03-01

    The purpose of this study is two-fold: (1) to develop a generic, life-cycle cost model for evaluating low-level, mixed waste remediation alternatives, and (2) to apply the model specifically, to estimate remediation costs for a site similar to the Fernald Environmental Management Project near Cincinnati, OH. Life-cycle costs for vitrification, cementation, and dry removal process technologies are estimated. Since vitrification is in a conceptual phase, computer simulation is used to help characterize the support infrastructure of a large scale vitrification plant. Cost estimating relationships obtained from the simulation data, previous cost estimates, available process data, engineering judgment, and expert opinion all provide input to an Excel based spreadsheet for generating cash flow streams. Crystal Ball, an Excel add-on, was used for discounting cash flows for net present value analysis. The resulting LCC data was then analyzed using multi-attribute decision analysis techniques with cost and remediation time as criteria. The analytical framework presented allows alternatives to be evaluated in the context of budgetary, social, and political considerations. In general, the longer the remediation takes, the lower the net present value of the process. This is true because of the time value of money and large percentage of the costs attributed to storage or disposal.

  19. Comparative life-cycle cost analysis for low-level mixed waste remediation alternatives. Technical report

    SciTech Connect

    Jackson, J.A.; White, T.P.; Kloeber, J.M.; Toland, R.J.; Cain, J.P.

    1995-03-01

    The purpose of this study is two-fold: (1) to develop a generic, life-cycle cost model for evaluating low-level, mixed waste remediation alternatives, and (2) to apply the model, specifically, to estimate remediation costs for a site similar to the Femald Environmental Management Project near Cincinnati, OH. Life-cycle costs for virtification, cementation, and dry removal process technologies are estimated. Since vitrification is in a conceptual phase, computer simulation is used to help characterize the support infrastructure of a large scale vitrification plant. Cost estimating relationships obtained from the simulation data, previous cost estimates, available process data, engineering judgment, and expert opinion all provide input to an Excel based spreadsheet for generating cash flow streams. Crystal Ball, an Excel add-on, was used for discounting cash flows for net present value analysis. The resulting LCC data was then analyzed using multi-attribute decision analysis techniques with cost and remediation time as criteria. The analytical framework presented allows alternatives to be evaluated in the context of budgetary, social, and political considerations. In general, the longer the remediation takes, the lower the net present value of the process.

  20. Treatment of sewage sludge in a thermophilic membrane reactor (TMR) with alternate aeration cycles.

    PubMed

    Collivignarelli, Maria Cristina; Castagnola, Federico; Sordi, Marco; Bertanza, Giorgio

    2015-10-01

    The management of sewage sludge is becoming a more and more important issue, both at national and international level, in particular due to the uncertain recovery/disposal future options. Therefore, it is clear that the development of new technologies that can mitigate the problem at the source by reducing sludge production is necessary, such as the European Directive 2008/98/EC prescribes. This work shows the results obtained with a thermophilic membrane reactor, for processing a biological sludge derived from a wastewater treatment plant (WWTP) that treats urban and industrial wastewater. Sewage sludge was treated in a thermophilic membrane reactor (TMR), at pilot-scale (1 m(3) volume), with alternate aeration cycles. The experimentation was divided into two phases: a "startup phase" during which, starting with a psychrophilic/mesophilic biomass, thermophilic conditions were progressively reached, while feeding a highly biodegradable substrate; the obtained thermophilic biomass was then used, in the "regime phase", to digest biological sludge which was fed to the plant. Good removal yields were observed: 64% and 57% for volatile solids (VS) and total COD (CODtot), respectively, with an average hydraulic retention time (HRT) equal to 20 d, an organic loading rate (OLR) of about 1.4-1.8 kg COD m(-3) d(-1) and aeration/non aeration cycles alternated every 4 h.

  1. Life-cycle cost and impacts: alternatives for managing KE basin sludge

    SciTech Connect

    Alderman, C.J.

    1997-06-27

    This document presents the results of a life-cycle cost and impacts evaluation of alternatives for managing sludge that will be removed from the K Basins. The two basins are located in the 100-K Area of the Hanford Site. This evaluation was conducted by Fluor Daniel Hanford, Inc. (FDH) and its subcontractors to support decisions regarding the ultimate disposition of the sludge. The long-range plan for the Hanford Site calls for spent nuclear fuel (SNF), sludge, debris, and water to be removed from the K East (KE) and K West (KW) Basins. This activity will be conducted as a removal action under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The scope of the CERCLA action will be limited to removing the SNF, sludge, debris, and water from the basins and transferring them to authorized facilities for interim storage and/or treatment and disposal. The scope includes treating the sludge and water in the 100-K Area prior to the transfer. Alternatives for the removal action are evaluated in a CERCLA engineering evaluation/cost analysis (EE/CA) and include different methods for managing sludge from the KE Basins. The scope of the removal action does not include storing, treating, or disposing of the sludge once it is transferred to the receiving facility and the EE/CA does not evaluate those downstream activities. This life-cycle evaluation goes beyond the EE/CA and considers the full life-cycle costs and impacts of dispositioning sludge.

  2. Mathematical model of alternative mechanism of telomere length maintenance

    NASA Astrophysics Data System (ADS)

    Kollár, Richard; Bod'ová, Katarína; Nosek, Jozef; Tomáška, L'ubomír

    2014-03-01

    Biopolymer length regulation is a complex process that involves a large number of biological, chemical, and physical subprocesses acting simultaneously across multiple spatial and temporal scales. An illustrative example important for genomic stability is the length regulation of telomeres—nucleoprotein structures at the ends of linear chromosomes consisting of tandemly repeated DNA sequences and a specialized set of proteins. Maintenance of telomeres is often facilitated by the enzyme telomerase but, particularly in telomerase-free systems, the maintenance of chromosomal termini depends on alternative lengthening of telomeres (ALT) mechanisms mediated by recombination. Various linear and circular DNA structures were identified to participate in ALT, however, dynamics of the whole process is still poorly understood. We propose a chemical kinetics model of ALT with kinetic rates systematically derived from the biophysics of DNA diffusion and looping. The reaction system is reduced to a coagulation-fragmentation system by quasi-steady-state approximation. The detailed treatment of kinetic rates yields explicit formulas for expected size distributions of telomeres that demonstrate the key role played by the J factor, a quantitative measure of bending of polymers. The results are in agreement with experimental data and point out interesting phenomena: an appearance of very long telomeric circles if the total telomere density exceeds a critical value (excess mass) and a nonlinear response of the telomere size distributions to the amount of telomeric DNA in the system. The results can be of general importance for understanding dynamics of telomeres in telomerase-independent systems as this mode of telomere maintenance is similar to the situation in tumor cells lacking telomerase activity. Furthermore, due to its universality, the model may also serve as a prototype of an interaction between linear and circular DNA structures in various settings.

  3. Phototoxicity: Its Mechanism and Animal Alternative Test Methods

    PubMed Central

    Park, Hyeonji; Lim, Kyung-Min

    2015-01-01

    The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential. PMID:26191378

  4. Carcinogenesis of nasopharyngeal carcinoma: an alternate hypothetical mechanism.

    PubMed

    Poh, Sharon Shuxian; Chua, Melvin Lee Kiang; Wee, Joseph T S

    2016-01-06

    Current proposed mechanisms implicate both early and latent Epstein-Barr virus (EBV) infection in the carcinogenic cascade, whereas epidemiological studies have always associated nasopharyngeal carcinoma (NPC) with early childhood EBV infection and with chronic ear, nose, and sinus conditions. Moreover, most patients with NPC present with IgA antibody titers to EBV capsid antigen (VCA-IgA), which can precede actual tumor presentation by several years. If early childhood EBV infection indeed constitutes a key event in NPC carcinogenesis, one would have to explain the inability to detect the virus in normal nasopharyngeal epithelium of patients at a high risk for EBV infection. It is perhaps possible that EBV resides within the salivary glands, instead of the epithelium, during latency. This claim is indirectly supported by observations that the East Asian phenotype shares the characteristics of an increased susceptibility to NPC and immature salivary gland morphogenesis, the latter of which is influenced by the association of salivary gland morphogenesis with an evolutionary variant of the human ectodysplasin receptor gene (EDAR), EDARV370A. Whether the immature salivary gland represents a more favorable nidus for EBV is uncertain, but in patients with infectious mononucleosis, EBV has been isolated in this anatomical organ. The presence of EBV-induced lymphoepitheliomas in the salivary glands and lungs further addresses the possibility of submucosal spread of the virus. Adding to the fact that the fossa of Rosen Müller contains a transformative zone active only in the first decade of life, one might be tempted to speculate the possibility of an alternative carcinogenic cascade for NPC that is perhaps not dissimilar to the model of human papillomavirus and cervical cancer.

  5. Mechanisms leading to reversible mechanical dysfunction in severe CAD: alternatives to myocardial stunning.

    PubMed

    Mazzadi, Alejandro N; André-Fouët, Xavier; Costes, Nicolas; Croisille, Pierre; Revel, Didier; Janier, Marc F

    2006-12-01

    Patients with severe chronic coronary artery disease (CAD) exhibit a highly altered myocardial pattern of perfusion, metabolism, and mechanical performance. In this context, the diagnosis of stunning remains elusive not only because of methodological and logistic considerations, but also because of the pathophysiological characteristics of the myocardium of these patients. In addition, a number of alternative pathophysiological mechanisms may act by mimicking the functional manifestations usually attributed to stunning. The present review describes three mechanisms that could theoretically lead to reversible mechanical dysfunction in these patients: myocardial wall stress, the tethering effect, and myocardial expression and release of auto- and paracrine agents. Attention is focused on the role of these mechanisms in scintigraphically "normal" regions (i.e., regions usually showing normal perfusion, glucose metabolism, and cellular integrity as assessed by nuclear imaging techniques), in which stunning is usually considered, but these mechanisms could also operate throughout the viable myocardium. We hypothesize that reversion of these three mechanisms could partially explain the unexpected functional benefit after reperfusion recently highlighted by high-spatial-resolution imaging techniques. PMID:16861690

  6. [The regulation mechanism of the female menstrual cycle].

    PubMed

    Yoshiki, N; Aso, T

    1997-11-01

    The hormonal patterns during menstrual cycle, which consist of cyclic alterations in gonadotropins, estradiol, and progesterone, are controlled by hypothalamic-pituitary-ovarian feedback mechanism. GnRH produced in hypothalamus acts on the pituitary cells to secrete FSH and LH, which stimulate the follicular development. The developed follicles secrete estradiol, progesterone, inhibin, activin, and follistatin. Estradiol and progesterone, at different concentrations and/or ratios, either positively or negatively control the feedback of hypothalamic-pituitary axis in regulating the secretion of GnRH, FSH and LH. Inhibin and follistatin selectively suppress, whereas activin enhances the secretion of FSH in the pituitary. Recently, various additional factors produced by the ovary have been identified to contribute to the follicular development by paracrine and/or autocrine regulation as well as to feedback on hypothalamic-pituitary unit.

  7. Life cycle comparison of waste-to-energy alternatives for municipal waste treatment in Chilean Patagonia.

    PubMed

    Bezama, Alberto; Douglas, Carla; Méndez, Jacqueline; Szarka, Nóra; Muñoz, Edmundo; Navia, Rodrigo; Schock, Steffen; Konrad, Odorico; Ulloa, Claudia

    2013-10-01

    The energy system in the Region of Aysén, Chile, is characterized by a strong dependence on fossil fuels, which account for up to 51% of the installed capacity. Although the implementation of waste-to-energy concepts in municipal waste management systems could support the establishment of a more fossil-independent energy system for the region, previous studies have concluded that energy recovery systems are not suitable from an economic perspective in Chile. Therefore, this work intends to evaluate these technical options from an environmental perspective, using life cycle assessment as a tool for a comparative analysis, considering Coyhaique city as a case study. Three technical alternatives were evaluated: (i) landfill gas recovery and flaring without energy recovery; (ii) landfill gas recovery and energy use; and (iii) the implementation of an anaerobic digestion system for the organic waste fraction coupled with energy recovery from the biogas produced. Mass and energy balances of the three analyzed alternatives have been modeled. The comparative LCA considered global warming potential, abiotic depletion and ozone layer depletion as impact categories, as well as required raw energy and produced energy as comparative regional-specific indicators. According to the results, the use of the recovered landfill gas as an energy source can be identified as the most environmentally appropriate solution for Coyhaique, especially when taking into consideration the global impact categories.

  8. Life cycle comparison of waste-to-energy alternatives for municipal waste treatment in Chilean Patagonia.

    PubMed

    Bezama, Alberto; Douglas, Carla; Méndez, Jacqueline; Szarka, Nóra; Muñoz, Edmundo; Navia, Rodrigo; Schock, Steffen; Konrad, Odorico; Ulloa, Claudia

    2013-10-01

    The energy system in the Region of Aysén, Chile, is characterized by a strong dependence on fossil fuels, which account for up to 51% of the installed capacity. Although the implementation of waste-to-energy concepts in municipal waste management systems could support the establishment of a more fossil-independent energy system for the region, previous studies have concluded that energy recovery systems are not suitable from an economic perspective in Chile. Therefore, this work intends to evaluate these technical options from an environmental perspective, using life cycle assessment as a tool for a comparative analysis, considering Coyhaique city as a case study. Three technical alternatives were evaluated: (i) landfill gas recovery and flaring without energy recovery; (ii) landfill gas recovery and energy use; and (iii) the implementation of an anaerobic digestion system for the organic waste fraction coupled with energy recovery from the biogas produced. Mass and energy balances of the three analyzed alternatives have been modeled. The comparative LCA considered global warming potential, abiotic depletion and ozone layer depletion as impact categories, as well as required raw energy and produced energy as comparative regional-specific indicators. According to the results, the use of the recovered landfill gas as an energy source can be identified as the most environmentally appropriate solution for Coyhaique, especially when taking into consideration the global impact categories. PMID:23988463

  9. Alternating stimulation of synergistic muscles during functional electrical stimulation cycling improves endurance in persons with spinal cord injury.

    PubMed

    Decker, M J; Griffin, L; Abraham, L D; Brandt, L

    2010-12-01

    Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used the standard "co-activation" protocol from the manufacturer of the FES cycle which involved intermittent simultaneous activation of the entire quadriceps muscle group for 400 ms. The other strategy was an "alternation" stimulation protocol which involved alternately stimulating the rectus femoris (RF) muscle for 100 ms and the vastus medialis (VM) and vastus lateralis (VL) muscles for 100 ms, with two sets with a 400 ms burst. Thus, during the alternation protocol, each of the muscle groups rested for two 100 ms "off" periods in each 400 ms burst. There was no difference in average cycling cadence (28 RPM) between the two protocols. The alternation stimulation protocol produced longer ride times and longer virtual distances traveled and used lower stimulation intensity levels with no differences in average MMG amplitudes compared to the co-activation protocol. These results demonstrate that FES-cycling performance can be enhanced by a synergistic muscle alternation stimulation strategy. PMID:20708950

  10. Alternating stimulation of synergistic muscles during functional electrical stimulation cycling improves endurance in persons with spinal cord injury.

    PubMed

    Decker, M J; Griffin, L; Abraham, L D; Brandt, L

    2010-12-01

    Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used the standard "co-activation" protocol from the manufacturer of the FES cycle which involved intermittent simultaneous activation of the entire quadriceps muscle group for 400 ms. The other strategy was an "alternation" stimulation protocol which involved alternately stimulating the rectus femoris (RF) muscle for 100 ms and the vastus medialis (VM) and vastus lateralis (VL) muscles for 100 ms, with two sets with a 400 ms burst. Thus, during the alternation protocol, each of the muscle groups rested for two 100 ms "off" periods in each 400 ms burst. There was no difference in average cycling cadence (28 RPM) between the two protocols. The alternation stimulation protocol produced longer ride times and longer virtual distances traveled and used lower stimulation intensity levels with no differences in average MMG amplitudes compared to the co-activation protocol. These results demonstrate that FES-cycling performance can be enhanced by a synergistic muscle alternation stimulation strategy.

  11. Mechanisms of brain evolution: regulation of neural progenitor cell diversity and cell cycle length.

    PubMed

    Borrell, Victor; Calegari, Federico

    2014-09-01

    In the last few years, several studies have revisited long-held assumptions in the field of brain development and evolution providing us with a fundamentally new vision on the mechanisms controlling its size and shape, hence function. Among these studies, some described hitherto unforeseeable subtypes of neural progenitors while others reinterpreted long-known observations about their cell cycle in alternative new ways. Most remarkably, this knowledge combined has allowed the generation of mammalian model organisms in which brain size and folding has been selectively increased giving us the means to understand the mechanisms underlying the evolution of the most complex and sophisticated organ. Here we review the key findings made in this area and make a few conjectures about their evolutionary meaning including the likelihood of Martians conquering our planet. PMID:24786671

  12. Assessment of Alternate Delivery Mechanisms for Asynchronous Adult Distance Learners.

    ERIC Educational Resources Information Center

    Usrey, Michael W.

    Within a course at the University of Colorado addressing the management of research and development, a comparison of alternate asynchronous delivery media was conducted. For the course session on the management of intellectual property, asynchronous students were given access to the VHS tapes traditionally utilized, plus World Wide Web-based and…

  13. Paying for College: Student Loans and Alternative Financing Mechanisms.

    ERIC Educational Resources Information Center

    Eureka Project, Sacramento, CA.

    As a part of a study on financing higher education in California, information is presented on student loans and alternative methods of financing. Part 1 reviews problems caused by a heavy reliance on the federal Guaranteed Student Loan program (GSL). It discusses troubles of the GSL program; the lack of policy purpose; program costs; defaults;…

  14. Mechanisms for synchrony and alternation in song interactions of the bushcricket Mecopoda elongata (Tettigoniidae: Orthoptera)

    PubMed Central

    Hartbauer, Manfred; Kratzer, Silvia; Steiner, Klaus; Römer, Heiner

    2014-01-01

    Males of the bushcricket Mecopoda elongata synchronise or alternate their chirps with their neighbours in an aggregation. Since synchrony is imperfect, leader and follower chirps are established in song interactions; females prefer leader chirps in phonotactic trials. Using playback experiments and simulations of song oscillator interactions, we investigate the mechanisms that result in synchrony and alternation, and the probability for the leader role in synchrony. A major predictor for the leader role of a male is its intrinsic chirp period, which varies in a population from 1.6 to 2.3 s. Faster singing males establish the leader role more often than males with longer chirp periods. The phase-response curve (PRC) of the song oscillators differs to other rhythmically calling or flashing insects, in that only the disturbed cycle is influenced in duration by a stimulus. This results in sustained leader or follower chirps of one male, when the intrinsic chirp periods of two males differ by 150 ms or more. By contrast, the individual shape of the male’s PRC has only little influence on the outcome of chirp interactions. The consequences of these findings for the evolution of synchrony in this species are discussed. PMID:15614532

  15. [Effects and mechanism of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem].

    PubMed

    Wang, Li-qin; Qi, Yu-chun; Dong, Yun-she; Peng, Qin; Guo, Shu-fang; He, Yun-long; Yan, Zhong-qing

    2015-11-01

    As a widespread natural phenomenon in the soil of middle and high latitude as well as high altitude, freeze-thawing cycles have a great influence on the nitrogen cycle of terrestrial ecosystem in non-growing season. Freeze-thawing cycles can alter the physicochemical and biological properties of the soil, which thereby affect the migration and transformation of soil nitrogen. The impacts of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem found in available studies remain inconsistent, the mechanism is still not clear, and the research methods also need to be further explored and innovated. So it is necessary to sum up and analyze the existing achievements in order to better understand the processes of soil nitrogen cycle subjected to freeze-thawing cycles. This paper reviewed the research progress in China and abroad about the effects and mechanisms of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem, including mineralization, immobilization, nitrification and denitrification, N leakage and gaseous loss, and analyzed the deficiencies of extant research. The possible key research topics that should be urgently paid more attention to in the future were also discussed.

  16. Chemisorption On Nanoparticles: An Alternative Mechanism For Hydrogen Storage

    SciTech Connect

    Williamson, A; Reboredo, F; Galli, G

    2004-04-09

    We present first principles, computational predictions of a porous, nano-structured semiconductor material that will reversibly store hydrogen for fuel cell applications. The material is competitive with current metal hydride storage materials, but contains only carbon and silicon, reducing both its cost and environmental impact. Additionally, unlike metal hydrides, the core skeleton structure of this material is unaltered when cycling from full hydrogen storage to full hydrogen depletion, removing engineering complications associated with expansion/contraction of the material.

  17. Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and Impacts of Key Design Alternatives: Preprint

    SciTech Connect

    Heath, G. A.; Burkhardt, J. J.; Turchi, C. S.

    2011-09-01

    Climate change and water scarcity are important issues for today's power sector. To inform capacity expansion decisions, hybrid life cycle assessment is used to evaluate a reference design of a parabolic trough concentrating solar power (CSP) facility located in Daggett, California, along four sustainability metrics: life cycle greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). This wet-cooled, 103 MW plant utilizes mined nitrate salts in its two-tank, thermal energy storage (TES) system. Design alternatives of dry-cooling, a thermocline TES, and synthetically-derived nitrate salt are evaluated. During its life cycle, the reference CSP plant is estimated to emit 26 g CO2eq per kWh, consume 4.7 L/kWh of water, and demand 0.40 MJeq/kWh of energy, resulting in an EPBT of approximately 1 year. The dry-cooled alternative is estimated to reduce life cycle water consumption by 77% but increase life cycle GHG emissions and CED by 8%. Synthetic nitrate salts may increase life cycle GHG emissions by 52% compared to mined. Switching from two-tank to thermocline TES configuration reduces life cycle GHG emissions, most significantly for plants using synthetically-derived nitrate salts. CSP can significantly reduce GHG emissions compared to fossil-fueled generation; however, dry-cooling may be required in many locations to minimize water consumption.

  18. Fundamental study of failure mechanisms of pressure vessels under thermo-mechanical cycling in multiphase environments

    NASA Astrophysics Data System (ADS)

    Penso Mula, Jorge Antonio

    Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling services have been well known problems in the petrochemical, power and nuclear industries. Published literature and industry surveys show that similar problems have been occurring during the last 50 years. Understanding the causes of cracking and bulging would lead to improvements in the reliability of these pressure vessels. This study attempts to add information required for improving the knowledge and fundamental understanding of these problems. Cracking and bulging, most often in the weld areas, commonly experienced in delayed coking units (e.g. coke drums) in oil refineries are typical examples. The coke drum was selected for this study because of the existing field experience and past industrial investigation results that were available to serve as the baseline references for the analytical studies performed for this dissertation. Another reason for selecting the delayed coking units for this study was due to their high economical yields. Shutting down these units would cause a high negative economic impact on the refinery operations. Several failure mechanisms were hypothesized. The finite element method was used to analyze these significant variables and to verify the hypotheses. In conclusion, a fundamental explanation of the occurrence of bulging and cracking in pressure vessels in multiphase environments has been developed. Several important factors have been identified, including the high convection coefficient of the boiling layer during filling and quenching, the mismatch in physical, thermal and mechanical properties in the dissimilar weld of the clad plates and process conditions such as heating and quenching rate and warming time. Material selection for coke drums should consider not only fatigue strength but also corrosion resistance at high temperatures and low temperatures. Cracking occurs due to low cycle fatigue and corrosion. The FEA

  19. Distribution of power output during cycling: impact and mechanisms.

    PubMed

    Atkinson, Greg; Peacock, Oliver; St Clair Gibson, Alan; Tucker, Ross

    2007-01-01

    We aim to summarise the impact and mechanisms of work-rate pacing during individual cycling time trials (TTs). Unlike time-to-exhaustion tests, a TT provides an externally valid model for examining how an initial work rate is chosen and maintained by an athlete during self-selected exercise. The selection and distribution of work rate is one of many factors that influence cycling speed. Mathematical models are available to predict the impact of factors such as gradient and wind velocity on cycling speed, but only a few researchers have examined the inter-relationships between these factors and work-rate distribution within a TT. When environmental conditions are relatively stable (e.g. in a velodrome) and the TT is >10 minutes, then an even distribution of work rate is optimal. For a shorter TT (< or = 10 minutes), work rate should be increased during the starting effort because this proportion of total race time is significant. For a very short TT (< or = 2 minutes), the starting effort should be maximal, since the time saved during the starting phase is predicted to outweigh any time lost during the final metres because of fatigue. A similar 'time saving' rationale underpins the advice that work rate should vary in parallel with any changes in gradient or wind speed during a road TT. Increasing work rate in headwind and uphill sections, and vice versa, decreases the variability in speed and, therefore, the total race time. It seems that even experienced cyclists naturally select a supraoptimal work rate at the start of a longer TT. Whether such a start can be 'blunted' through coaching or the monitoring of psychophysiological variables is unknown. Similarly, the extent to which cyclists can vary and monitor work rate during a TT is unclear. There is evidence that sub-elite cyclists can vary work rate by +/-5% the average for a TT lasting 25-60 minutes, but such variability might be difficult with high-performance cyclists whose average work rate during a TT is

  20. Genomic Scars Generated by Polymerase Theta Reveal the Versatile Mechanism of Alternative End-Joining

    PubMed Central

    van Schendel, Robin; van Heteren, Jane; Welten, Richard; Tijsterman, Marcel

    2016-01-01

    For more than half a century, genotoxic agents have been used to induce mutations in the genome of model organisms to establish genotype-phenotype relationships. While inaccurate replication across damaged bases can explain the formation of single nucleotide variants, it remained unknown how DNA damage induces more severe genomic alterations. Here, we demonstrate for two of the most widely used mutagens, i.e. ethyl methanesulfonate (EMS) and photo-activated trimethylpsoralen (UV/TMP), that deletion mutagenesis is the result of polymerase Theta (POLQ)-mediated end joining (TMEJ) of double strand breaks (DSBs). This discovery allowed us to survey many thousands of available C. elegans deletion alleles to address the biology of this alternative end-joining repair mechanism. Analysis of ~7,000 deletion breakpoints and their cognate junctions reveals a distinct order of events. We found that nascent strands blocked at sites of DNA damage can engage in one or more cycles of primer extension using a more downstream located break end as a template. Resolution is accomplished when 3’ overhangs have matching ends. Our study provides a step-wise and versatile model for the in vivo mechanism of POLQ action, which explains the molecular nature of mutagen-induced deletion alleles. PMID:27755535

  1. 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

  2. A Freshwater Starvation Mechanism for Dansgaard-Oeschger Cycles

    NASA Astrophysics Data System (ADS)

    Wolff, E. W.; Hewitt, I.; Fowler, A.; Clark, C.; Evatt, G. W.; Munday, D. R.; Stokes, C.

    2014-12-01

    Many northern hemisphere climate records, particularly those from around the North Atlantic, show a series of rapid climate changes that recurred on centennial to millennial timescales throughout most of the last glacial period. These Dansgaard-Oeschger (D-O) sequences are observed most prominently in Greenland ice cores, although they have a global signature, including an out of phase Antarctic signal. They consist of warming jumps of order 10°C, occurring in typically 40 years, followed generally by a slow cooling (Greenland Interstadial, GI) lasting between a few centuries and a few millennia, and then a final rapid temperature drop into a cold Greenland Stadial (GS) that lasts for a similar period. The most distinctive feature of D-O cycles is the rapid warming event, often attributed to a sudden change in the strength of the Atlantic meridional overturning circulation (AMOC). Recent work has suggested that AMOC is most easily disrupted by freshwater delivered through the Arctic. We suggest that the proposed AMOC changes may have occurred as part of a natural oscillation, in which runoff from the Laurentide ice sheet into the Arctic is controlled by temperature around the North Atlantic. The Arctic buffers the salinity changes, but under warm conditions, high runoff eventually leads to water entering the North Atlantic with low enough salinity to switch AMOC into its weaker state. Under the colder conditions now prevailing, the Arctic is starved of runoff, and the salinity rises until a further switch occurs. Contrary to many previous studies, this mechanism does not require large freshwater pulses to the North Atlantic. Instead, steady changes in ice-sheet runoff, driven by the AMOC, lead to a naturally arising oscillator, in which the rapid warmings come about because the Arctic Ocean is starved of freshwater. The changing size of the ice sheets would have affected the magnitude and extent of runoff, and we suggest that this may provide a simple explanation

  3. Small molecules reveal an alternative mechanism of Bax activation

    PubMed Central

    Brahmbhatt, Hetal; Uehling, David; Al-awar, Rima; Leber, Brian; Andrews, David

    2016-01-01

    The pro-apoptotic protein Bax commits a cell to death by permeabilizing the mitochondrial outer membrane (MOM). To obtain small-molecule probes for elucidating the molecular mechanism(s) of Bax activation, we screened for compounds that induced Bax-mediated liposome permeabilization. We identified five structurally different small molecules that promoted both Bax targeting to and oligomerization at membranes. All five compounds initiated Bax oligomerization in the absence of membranes by a mechanism unlike Bax activation by Bcl-2 homology 3 domain (BH3) proteins. Some of the compounds induced Bax/Bak-dependent apoptosis in cells. Activation of Bax by the most active compound was poorly inhibited by the anti-apoptotic protein Bcl-XL and requires a cysteine residue at position 126 of Bax that is not required for activation by BH3 proteins. Our results reveal a novel pathway for Bax activation independent of pro-apoptotic BH3 proteins that may have important implications for the regulation of Bax activity in cells. PMID:26916338

  4. Molecular mechanisms creating bistable switches at cell cycle transitions

    PubMed Central

    Verdugo, Anael; Vinod, P. K.; Tyson, John J.; Novak, Bela

    2013-01-01

    Progression through the eukaryotic cell cycle is characterized by specific transitions, where cells move irreversibly from stage i−1 of the cycle into stage i. These irreversible cell cycle transitions are regulated by underlying bistable switches, which share some common features. An inhibitory protein stalls progression, and an activatory protein promotes progression. The inhibitor and activator are locked in a double-negative feedback loop, creating a one-way toggle switch that guarantees an irreversible commitment to move forward through the cell cycle, and it opposes regression from stage i to stage i−1. In many cases, the activator is an enzyme that modifies the inhibitor in multiple steps, whereas the hypo-modified inhibitor binds strongly to the activator and resists its enzymatic activity. These interactions are the basis of a reaction motif that provides a simple and generic account of many characteristic properties of cell cycle transitions. To demonstrate this assertion, we apply the motif in detail to the G1/S transition in budding yeast and to the mitotic checkpoint in mammalian cells. Variations of the motif might support irreversible cellular decision-making in other contexts. PMID:23486222

  5. Species-driven changes in nitrogen cycling can provide a mechanism for plant invasions.

    PubMed

    Laungani, Ramesh; Knops, Johannes M H

    2009-07-28

    Traits that permit successful invasions have often seemed idiosyncratic, and the key biological traits identified vary widely among species. This fundamentally limits our ability to determine the invasion potential of a species. However, ultimately, successful invaders must have positive growth rates that longer term result in higher biomass accumulation than competing established species. In many terrestrial ecosystems nitrogen limits plant growth, and is a key factor determining productivity and the outcome of competition among species. Plant nitrogen use may provide a powerful framework to evaluate the invasive potential of a species in nitrogen-limiting ecosystems. Six mechanisms influence plant nitrogen use or acquisition: photosynthetic tissue allocation, photosynthetic nitrogen use efficiency, nitrogen fixation, nitrogen-leaching losses, gross nitrogen mineralization, and plant nitrogen residence time. Here we show that among these alternatives, the key mechanism allowing invasion for Pinus strobus into nitrogen limited grasslands was its higher nitrogen residence time. This higher nitrogen residence time created a positive feedback that redistributed nitrogen from the soil into the plant. This positive feedback allowed P. strobus to accumulate twice as much nitrogen in its tissues and four times as much nitrogen to photosynthetic tissues, as compared with other plant species. In turn, this larger leaf nitrogen pool increased total plant carbon gain of P. strobus two- to sevenfold as compared with other plant species. Thus our data illustrate that plant species can change internal ecosystem nitrogen cycling feedbacks and this mechanism can allow them to gain a competitive advantage over other plant species. PMID:19592506

  6. Species-driven changes in nitrogen cycling can provide a mechanism for plant invasions.

    PubMed

    Laungani, Ramesh; Knops, Johannes M H

    2009-07-28

    Traits that permit successful invasions have often seemed idiosyncratic, and the key biological traits identified vary widely among species. This fundamentally limits our ability to determine the invasion potential of a species. However, ultimately, successful invaders must have positive growth rates that longer term result in higher biomass accumulation than competing established species. In many terrestrial ecosystems nitrogen limits plant growth, and is a key factor determining productivity and the outcome of competition among species. Plant nitrogen use may provide a powerful framework to evaluate the invasive potential of a species in nitrogen-limiting ecosystems. Six mechanisms influence plant nitrogen use or acquisition: photosynthetic tissue allocation, photosynthetic nitrogen use efficiency, nitrogen fixation, nitrogen-leaching losses, gross nitrogen mineralization, and plant nitrogen residence time. Here we show that among these alternatives, the key mechanism allowing invasion for Pinus strobus into nitrogen limited grasslands was its higher nitrogen residence time. This higher nitrogen residence time created a positive feedback that redistributed nitrogen from the soil into the plant. This positive feedback allowed P. strobus to accumulate twice as much nitrogen in its tissues and four times as much nitrogen to photosynthetic tissues, as compared with other plant species. In turn, this larger leaf nitrogen pool increased total plant carbon gain of P. strobus two- to sevenfold as compared with other plant species. Thus our data illustrate that plant species can change internal ecosystem nitrogen cycling feedbacks and this mechanism can allow them to gain a competitive advantage over other plant species.

  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. Alternative Contrast Mechanisms in High Field MR Microscopy.

    NASA Astrophysics Data System (ADS)

    Engelhardt, Robert Thomas

    1995-01-01

    In high-field MR Microscopy, the T_1 relaxation times may become long and converge while the T_2 relaxation times may become short and converge. As a result, much of the contrast is due solely to differences in spin density. The use of T_{1rho} as an alternative contrast parameter in high-field MR Microscopy has been explored here. To this end, MR Microscopy experiments have been performed using 2.0 and 9.4 Tesla Bruker MRI systems. Spectroscopy experiments at 9.4 Tesla were performed on several phantoms (5.75% agar gel, 1.0 mM MnCl_2, 7.3% and 20% gelatin). Imaging experiments were performed on two, 17.5 day old, perfusion fixed, mouse embryos, embedded in 7.3% gelatin to minimize drying and susceptibility differences. The relaxation times, T_1, T _2, and T_{1rho }, the signal to noise ratios (SNR) and contrast to noise ratios (CNR), have been measured for several types of tissue. The T_{1rho} relaxation times were measured at four locking field strengths, 0.7, 0.9, 1.3 and 1.7 G. T_1 and T_2 imaging experiments were performed using a conventional spin warp imaging sequence. T_{1rho } imaging experiments were performed using a presaturating spin locking pulse, followed by a conventional spin warp imaging sequence. Muscle, diencephalon, lung and liver were chosen for the relaxation time measurements as they offered both good tissue specificity and size. Both static and locking field dispersion of T _{1rho} were observed in the selected mouse embryo tissues. The observed T _{1rho} relaxation times were generally longer than the T_2 relaxation times, increased with locking field strength, and were consistently shorter at 9.4 Tesla than at 2.0 Tesla. The static field dispersion of T_ {1rho} and T_2 are both believed to be due, in part, to diffusion losses through susceptibility induced gradients. The losses are much smaller in the T_{1rho} images, and decrease as the locking pulse is increased. Finally, under certain circumstances, T_{1rho }-weighting could produce

  9. Cross-dressing: an alternative mechanism for antigen presentation.

    PubMed

    Campana, Stefania; De Pasquale, Claudia; Carrega, Paolo; Ferlazzo, Guido; Bonaccorsi, Irene

    2015-12-01

    Cross-dressing involves the transfer of preformed functional peptide-MHC complexes from the surface of donor cells to recipient cells, such as dendritic cells (DCs). These cross-dressed cells might eventually present the intact, unprocessed peptide-MHC complexes to T lymphocytes. In this review we will discuss some recent findings concerning the intercellular transfer of preformed MHC complexes and the possible mechanisms by which the transfer may occur. We will report evidences showing that both MHC class I and MHC class II functional complexes might be transferred, highlighting the physiological relevance of these cross-dressed cells for the presentation of exogenous antigens to both cytotoxic and helper T lymphocytes.

  10. Alternative mechanisms of receptor editing in autoreactive B cells.

    PubMed

    Kalinina, Olga; Doyle-Cooper, Colleen M; Miksanek, Jennifer; Meng, Wenzhao; Prak, Eline Luning; Weigert, Martin G

    2011-04-26

    Pathogenic anti-DNA antibodies expressed in systemic lupus erythematosis bind DNA mainly through electrostatic interactions between the positively charged Arg residues of the antibody complementarity determining region (CDR) and the negatively charged phosphate groups of DNA. The importance of Arg in CDR3 for DNA binding has been shown in mice with transgenes coding for anti-DNA V(H) regions; there is also a close correlation between arginines in CDR3 of antibodies and DNA binding. Codons for Arg can readily be formed by V(D)J rearrangement; thereby, antibodies that bind DNA are part of the preimmune repertoire. Anti-DNAs in healthy mice are regulated by receptor editing, a mechanism that replaces κ light (L) chains compatible with DNA binding with κ L chains that harbor aspartic residues. This negatively charged amino acid is thought to neutralize Arg sites in the V(H). Editing by replacement is allowed at the κ locus, because the rearranged VJ is nested between unrearranged Vs and Js. However, neither λ nor heavy (H) chain loci are organized so as to allow such second rearrangements. In this study, we analyze regulation of anti-DNA H chains in mice that lack the κ locus, κ-/κ- mice. These mice show that the endogenous preimmune repertoire does indeed include a high frequency of antibodies with Arg in their CDR3s (putative anti-DNAs) and they are associated mainly with the editor L chain λx. The editing mechanisms in the case of λ-expressing B cells include L chain allelic inclusion and V(H) replacement.

  11. Beyond membrane channelopathies: alternative mechanisms underlying complex human disease

    PubMed Central

    Boudoulas, Konstantinos Dean; Mohler, Peter J

    2011-01-01

    Over the past fifteen years, our understanding of the molecular mechanisms underlying human disease has flourished in large part due to the discovery of gene mutations linked with membrane ion channels and transporters. In fact, ion channel defects (“channelopathies” — the focus of this review series) have been associated with a spectrum of serious human disease phenotypes including cystic fibrosis, cardiac arrhythmia, diabetes, skeletal muscle defects, and neurological disorders. However, we now know that human disease, particularly excitable cell disease, may be caused by defects in non-ion channel polypeptides including in cellular components residing well beneath the plasma membrane. For example, over the past few years, a new class of potentially fatal cardiac arrhythmias has been linked with cytoplasmic proteins that include sub-membrane adapters such as ankyrin-B (ANK2), ankyrin-G (ANK3), and alpha-1 syntrophin, membrane coat proteins including caveolin-3 (CAV3), signaling platforms including yotiao (AKAP9), and cardiac enzymes (GPD1L). The focus of this review is to detail the exciting role of lamins, yet another class of gene products that have provided elegant new insight into human disease. PMID:21642948

  12. Correlations using the NREM-REM sleep cycle frequency support distinct regulation mechanisms for REM and NREM sleep.

    PubMed

    Le Bon, O; Staner, L; Rivelli, S K; Hoffmann, G; Pelc, I; Linkowski, P

    2002-07-01

    Polysomnograms of most homeothermic species distinguish two states, rapid eye movement (REM) and non-REM (NREM) sleep. These alternate several times during the night for reasons and following rules that remain poorly understood. It is unknown whether each state has its own function and regulation or whether they represent two facets of the same process. The present study compared the mean REM/NREM sleep ratio and the mean number of NREM-REM sleep cycles across 3 consecutive nights. The rationale was that, if REM and NREM sleep are tightly associated, their ratio should be comparable whatever the cycle frequency in the night. Twenty-six healthy subjects of both sexes were recorded at their home for 4 consecutive nights. The correlation between the REM/NREM sleep ratio and the number of cycles was highly significant. Of the two sleep components, REM sleep was associated to the number of cycles, whereas NREM sleep was not. This suggests that the relationship between REM sleep and NREM sleep is rather weak within cycles, does not support the concept of NREM-REM sleep cycles as miniature units of the sleep process, and favors the concept of distinct mechanisms of regulation for the two components.

  13. Alternative Physical Therapy Protocol Using a Cycle Ergometer During Hospital Rehabilitation of Coronary Artery Bypass Grafting: a Clinical Trial

    PubMed Central

    Trevisan, Margarete Diprat; Lopes, Diene Gomes Colvara; de Mello, Renato Gorga Bandeira; Macagnan, Fabrício Edler; Kessler, Adriana

    2015-01-01

    OBJECTIVE To compare the efficacy of a cycle ergometer-based exercise program to a standard protocol on the increment of the maximum distance walked during the six-minute walk test in the postoperative rehabilitation of patients submitted to coronary artery bypass grafting. METHODS A controlled clinical trial pilot, blinded to the outcome, enrolled subjects who underwent coronary artery bypass grafting in a hospital from Southern Brazil. Subjects were designated for the standard physical rehabilitation protocol or to an alternative cycle ergometer-based protocol through simple random sampling. The primary outcome was the difference in the maximum distance walked in the six-minute walk test before and after the allocated intervention. RESULTS Twenty-four patients were included in the analysis, 10 in the standard protocol and 14 in the alternative protocol group. There was an increment in the maximum distance walked in both groups, and borderline superiority in the intervention group comparing to the control group (312.2 vs. 249.7; P=0.06). CONCLUSION There was an increase in the maximum distance walked in the alternative protocol compared to the standard protocol. Thus, it is postulated that the use of a cycle ergometer can be included in physical rehabilitation in the hospital phase of postoperative coronary artery bypass grafting. However, randomized studies with larger sample size should be conducted to assess the significance of these findings. PMID:26934400

  14. Accelerated Thermal Cycling and Failure Mechanisms for BGA and CSP Assemblies

    NASA Technical Reports Server (NTRS)

    Ghaffarian, Reza

    2000-01-01

    This paper reviews the accelerated thermal cycling test methods that are currently used by industry to characterize the interconnect reliability of commercial-off-the-shelf (COTS) ball grid array (BGA) and chip scale package (CSP) assemblies. Acceleration induced failure mechanisms varied from conventional surface mount (SM) failures for CSPs. Examples of unrealistic life projections for other CSPs are also presented. The cumulative cycles to failure for ceramic BGA assemblies performed under different conditions, including plots of their two Weibull parameters, are presented. The results are for cycles in the range of -30 C to 100 C, -55 C to 100 C, and -55 C to 125 C. Failure mechanisms as well as cycles to failure for thermal shock and thermal cycling conditions in the range of -55 C to 125 C were compared. Projection to other temperature cycling ranges using a modified Coffin-Manson relationship is also presented.

  15. Simulations of heart mechanics over the cardiac cycle

    NASA Astrophysics Data System (ADS)

    Tavoularis, Stavros; Doyle, Matthew; Bourgault, Yves

    2009-11-01

    This study is concerned with the numerical simulation of blood flow and myocardium motion with fluid-structure interaction of the left ventricle (LV) of a canine heart over the entire cardiac cycle. The LV geometry is modeled as a series of nested prolate ellipsoids and is capped with cylindrical tubes representing the inflow and outflow tracts. The myocardium is modeled as a multi-layered, slightly compressible, transversely isotropic, hyperelastic material, with each layer having different principal directions to approximate the fibrous structure. Blood is modeled as a slightly compressible Newtonian fluid. Blood flow into and out of the LV is driven by left atrial and aortic pressures applied at the distal ends of the inflow and outflow tracts, respectively, along with changes in the stresses in the myocardium caused by time-dependent changes in its material properties, which simulate the cyclic contraction and relaxation of the muscle fibers. Numerical solutions are obtained with the use of a finite element code. The computed temporal and spatial variations of pressure and velocity in the blood and stresses and strains in the myocardium will be discussed and compared to physiological data. The variation of the LV cavity volume over the cardiac cycle will also be discussed.

  16. Progress of Stirling cycle analysis and loss mechanism characterization

    NASA Technical Reports Server (NTRS)

    Tew, R. C., Jr.

    1986-01-01

    An assessment of Stirling engine thermodynamic modeling and design codes shows a general deficiency; this deficiency is due to poor understanding of the fluid flow and heat transfer phenomena that occur in the oscillating flow and pressure level environment within the engines. Stirling engine thermodynamic loss mechanisms are listed. Several experimental and computational research efforts now underway to characterize various loss mechanisms are reviewed. The need for additional experimental rigs and rig upgrades is discussed. Recent developments and current efforts in Stirling engine thermodynamic modeling are also reviewed.

  17. Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae.

    PubMed

    van Rossum, Harmen M; Kozak, Barbara U; Niemeijer, Matthijs S; Duine, Hendrik J; Luttik, Marijke A H; Boer, Viktor M; Kötter, Peter; Daran, Jean-Marc G; van Maris, Antonius J A; Pronk, Jack T

    2016-05-01

    Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction.

  18. Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae.

    PubMed

    van Rossum, Harmen M; Kozak, Barbara U; Niemeijer, Matthijs S; Duine, Hendrik J; Luttik, Marijke A H; Boer, Viktor M; Kötter, Peter; Daran, Jean-Marc G; van Maris, Antonius J A; Pronk, Jack T

    2016-05-01

    Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction. PMID:26895788

  19. Mitochondrial Mechanisms of Redox Cycling Agents Implicated in Parkinson's Disease

    PubMed Central

    Lopert, Pamela

    2016-01-01

    Environmental agents have been implicated in Parkinson's disease (PD) based on epidemiological studies and the ability of toxicants to replicate features of PD. However, the precise mechanisms by which toxicants induce dopaminergic toxicity observed in the idiopathic form of PD remain to be fully understood. The roles of ROS and mitochondria are strongly suggested in the mechanisms by which these toxicants exert dopaminergic toxicity. There are marked differences and similarities shared by the toxicants in increasing steady-state levels of mitochondrial ROS. Furthermore, toxicants increase steady-state mitochondrial ROS levels by stimulating the production, inhibiting the antioxidant pathways of both. This review will focus on the role of mitochondria and ROS in PD associated with environmental exposures to redox-based toxicants. PMID:25749885

  20. Life-cycle assessment of municipal solid waste management alternatives with consideration of uncertainty: SIWMS development and application

    SciTech Connect

    El Hanandeh, Ali; El-Zein, Abbas

    2010-05-15

    This paper describes the development and application of the Stochastic Integrated Waste Management Simulator (SIWMS) model. SIWMS provides a detailed view of the environmental impacts and associated costs of municipal solid waste (MSW) management alternatives under conditions of uncertainty. The model follows a life-cycle inventory approach extended with compensatory systems to provide more equitable bases for comparing different alternatives. Economic performance is measured by the net present value. The model is verified against four publicly available models under deterministic conditions and then used to study the impact of uncertainty on Sydney's MSW management 'best practices'. Uncertainty has a significant effect on all impact categories. The greatest effect is observed in the global warming category where a reversal of impact direction is predicted. The reliability of the system is most sensitive to uncertainties in the waste processing and disposal. The results highlight the importance of incorporating uncertainty at all stages to better understand the behaviour of the MSW system.

  1. Assessment of potential impacts of municipal solid waste treatment alternatives by using life cycle approach: a case study in Vietnam.

    PubMed

    Thanh, Nguyen Phuc; Matsui, Yasuhiro

    2013-10-01

    In Vietnam, most of municipal solid waste (MSW) is disposed of at open dumping and landfill sites, and the methane gas from waste is the un-ignorable source of greenhouse gas (GHG) emission. It is indispensable to explore the possibility for GHG mitigation in MSW management. The objective of this study was to estimate alternative waste treatment practices towards the GHG emission mitigation, energy consumption and generation, reduction of landfill volume, and various benefits for proposing the appropriate selection by scenario analyses for representative Vietnam's cities. Impacts were calculated by utilizing life cycle assessment (LCA) method. A literature review survey on the current applicability of LCA database for assessing impacts from waste sector in developing countries, especially for Vietnam, was carried out. This study assessed the contribution of alternative solid waste treatment practices. The result showed that, except investment and operation costs, incineration with energy recovery seems the suitable alternative for treating waste from representative cities of Vietnam according to reduction of GHG emission and waste burden to landfill sites and energy recovery and generation. Besides, MSW composition was identified as an important factor directly influencing to impacts as well as other products and benefits of waste treatment alternatives. Reliable data on waste composition are indispensable for assessing to choose, improve, or plan the waste treatment practices towards sustainable development. PMID:23475528

  2. Benefits and risks of emerging technologies: integrating life cycle assessment and decision analysis to assess lumber treatment alternatives.

    PubMed

    Tsang, Michael P; Bates, Matthew E; Madison, Marcus; Linkov, Igor

    2014-10-01

    Assessing the best options among emerging technologies (e.g., new chemicals, nanotechnologies) is complicated because of trade-offs across benefits and risks that are difficult to quantify given limited and fragmented availability of information. This study demonstrates the integration of multicriteria decision analysis (MCDA) and life cycle assessment (LCA) to address technology alternative selection decisions. As a case study, prioritization of six lumber treatment alternatives [micronized copper quaternary (MCQ); alkaline copper quaternary (ACQ); water-borne copper naphthenate (CN); oil-borne copper naphthenate (CNo); water-borne copper quinolate (CQ); and water-borne zinc naphthenate (ZN)] for military use are considered. Multiattribute value theory (MAVT) is used to derive risk and benefit scores. Risk scores are calculated using a cradle-to-gate LCA. Benefit scores are calculated by scoring of cost, durability, and corrosiveness criteria. Three weighting schemes are used, representing Environmental, Military and Balanced stakeholder perspectives. Aggregated scores from all three perspectives show CQ to be the least favorable alterative. MCQ is identified as the most favorable alternative from the Environmental stakeholder perspective. From the Military stakeholder perspective, ZN is determined to be the most favorable alternative, followed closely by MCQ. This type of scoring and ranking of multiple heterogeneous criteria in a systematic and transparent way facilitates better justification of technology selection and regulation.

  3. Benefits and risks of emerging technologies: integrating life cycle assessment and decision analysis to assess lumber treatment alternatives.

    PubMed

    Tsang, Michael P; Bates, Matthew E; Madison, Marcus; Linkov, Igor

    2014-10-01

    Assessing the best options among emerging technologies (e.g., new chemicals, nanotechnologies) is complicated because of trade-offs across benefits and risks that are difficult to quantify given limited and fragmented availability of information. This study demonstrates the integration of multicriteria decision analysis (MCDA) and life cycle assessment (LCA) to address technology alternative selection decisions. As a case study, prioritization of six lumber treatment alternatives [micronized copper quaternary (MCQ); alkaline copper quaternary (ACQ); water-borne copper naphthenate (CN); oil-borne copper naphthenate (CNo); water-borne copper quinolate (CQ); and water-borne zinc naphthenate (ZN)] for military use are considered. Multiattribute value theory (MAVT) is used to derive risk and benefit scores. Risk scores are calculated using a cradle-to-gate LCA. Benefit scores are calculated by scoring of cost, durability, and corrosiveness criteria. Three weighting schemes are used, representing Environmental, Military and Balanced stakeholder perspectives. Aggregated scores from all three perspectives show CQ to be the least favorable alterative. MCQ is identified as the most favorable alternative from the Environmental stakeholder perspective. From the Military stakeholder perspective, ZN is determined to be the most favorable alternative, followed closely by MCQ. This type of scoring and ranking of multiple heterogeneous criteria in a systematic and transparent way facilitates better justification of technology selection and regulation. PMID:25209330

  4. Three high duty cycle, space-qualified mechanisms

    NASA Technical Reports Server (NTRS)

    Akin, David; Horber, Ralph; Wolfson, Jake

    1993-01-01

    The Michelson Doppler Imager (MDI) is a scientific instrument aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. In 1995, the spacecraft will be put into a halo orbit about the L1 Lagrangian point (equal Sun and Earth gravity). The MDI looks at the sun continuously and takes a picture with a large format CCD camera every 3 seconds. The design goal of the mission is 6 years, so over 60 million pictures will be taken. The sun, being a high intensity source, provides a signal with a single pixel noise level of 0.2 percent. Many images are combined to measure the oscillatory motion of the sun so very high performance is required of the mechanisms in order that they not add noise to the data. The MDI instrument is made up of two parts, the electronics package and the optics package. This paper describes the design and testing of three mechanisms on the MDI which are required to operate large numbers of times.

  5. Alternate sulfate thermochemical hydrogen cycles for use with nuclear process heat

    SciTech Connect

    Bowman, M.G.

    1981-01-01

    The chemical reactions in the bismuth sulfate-sulfuric acid and magnesium sulfate-magnesium iodide cycles are discussed. Cycles based on solid decomposition reactions are better suited for high temperature isothermal heat sources than for gas cooled reactors. The bismuth cycle might possibly be adapted to a high temperature gas cooled system since the equilibrium dessociation pressure reaches one atmosphere at approximately 1035K and additional heat is required at lower temperatures to dry the solid and effect the low temperature reactions required to close the cycle. Two methods for conducting high temperature solid decomposition operations were tested. The first system involved a rotary kiln, which was used to study the decomposition of ZnSO/sub 4/ (to ZnO), La/sub 2/(SO/sub 4/)/sub 3/ (to La/sub 2/O/sub 2/SO/sub 4/) and Co/sub 3/O/sub 4/ (to CoO). The results of these studies, and some runs with Bi/sub 2/O(SO/sub 4/)/sub 2/ (to form Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/) are tabulated. Early attempts to study Bi/sub 2/O(SO/sub 4/)/sub 2/ decomposition in a fluidized bed system were unsuccessful since these sulfate particles would not fluidize satisfactorily. Therefore, a dual-particle fluidized bed system was constructed for use with rapid, high temperature decomposition reactions. The dual-particle fluidized bed concept was tested by studies of ZnSO/sub 4/ decomposition. In these experiments, a constant flow of argon carrier gas was passed through the fluidized bed and the quantity of ZnSO/sub 4/ varied to obtain different mol ratios of carrier gas to sulfate feed. Temperatures were measured by means of a thermocouple on the exterior of the quartz tube containing the fluidized bed. The results from two series of experiments are tabulated.

  6. Microstructural fracture mechanics in high-cycle fatigue

    SciTech Connect

    Rios, E.R. de los; Navarro, A.

    1997-12-31

    Microstructural Fracture Mechanics principles are used to develop a model of crack growth in long life fatigue. In its simplest form microstructural modelling considers the material as a polycrystal of uniform grain size D, with a crack system divided into three zones: the crack, the plastic zone and the microstructural barrier zone. The solution of the equilibrium equation allows for the calculation of the stresses sustained by the crack wake, plastic zone, barrier zone and elastic enclave, and the crack tip plastic displacement {phi}. Crack growth rate is calculated through a Paris type relationship in terms of {phi}, i.e., da/dN = C{phi}{sup n}. Conditions for crack arrest and instability are established.

  7. 45 CFR 148.128 - State flexibility in individual market reforms-alternative mechanisms.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 1 2011-10-01 2011-10-01 false State flexibility in individual market reforms-alternative mechanisms. 148.128 Section 148.128 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES... Requirements Relating to Access and Renewability of Coverage § 148.128 State flexibility in individual...

  8. 45 CFR 148.128 - State flexibility in individual market reforms-alternative mechanisms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 1 2013-10-01 2013-10-01 false State flexibility in individual market reforms-alternative mechanisms. 148.128 Section 148.128 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES... Requirements Relating to Access and Renewability of Coverage § 148.128 State flexibility in individual...

  9. 45 CFR 148.128 - State flexibility in individual market reforms-alternative mechanisms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 45 Public Welfare 1 2012-10-01 2012-10-01 false State flexibility in individual market reforms-alternative mechanisms. 148.128 Section 148.128 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES... Requirements Relating to Access and Renewability of Coverage § 148.128 State flexibility in individual...

  10. 45 CFR 148.128 - State flexibility in individual market reforms-alternative mechanisms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 1 2014-10-01 2014-10-01 false State flexibility in individual market reforms-alternative mechanisms. 148.128 Section 148.128 Public Welfare Department of Health and Human Services... Requirements Relating to Access and Renewability of Coverage § 148.128 State flexibility in individual...

  11. Toxic emissions from mobile sources: a total fuel-cycle analysis for conventional and alternative fuel vehicles.

    PubMed

    Winebrake, J J; Wang, M Q; He, D

    2001-07-01

    Mobile sources are among the largest contributors of four hazardous air pollutants--benzene, 1,3-butadiene, acetaldehyde, and formaldehyde--in urban areas. At the same time, federal and state governments are promoting the use of alternative fuel vehicles as a means to curb local air pollution. As yet, the impact of this movement toward alternative fuels with respect to toxic emissions has not been well studied. The purpose of this paper is to compare toxic emissions from vehicles operating on a variety of fuels, including reformulated gasoline (RFG), natural gas, ethanol, methanol, liquid petroleum gas (LPG), and electricity. This study uses a version of Argonne National Laboratory's Greenhouse Gas, Regulated Emissions, and Energy Use in Transportation (GREET) model, appropriately modified to estimate toxic emissions. The GREET model conducts a total fuel-cycle analysis that calculates emissions from both downstream (e.g., operation of the vehicle) and upstream (e.g., fuel production and distribution) stages of the fuel cycle. We find that almost all of the fuels studied reduce 1,3-butadiene emissions compared with conventional gasoline (CG). However, the use of ethanol in E85 (fuel made with 85% ethanol) or RFG leads to increased acetaldehyde emissions, and the use of methanol, ethanol, and compressed natural gas (CNG) may result in increased formaldehyde emissions. When the modeling results for the four air toxics are considered together with their cancer risk factors, all the fuels and vehicle technologies show air toxic emission reduction benefits.

  12. Life cycle assessment of a parabolic trough concentrating solar power plant and the impacts of key design alternatives.

    PubMed

    Burkhardt, John J; Heath, Garvin A; Turchi, Craig S

    2011-03-15

    Climate change and water scarcity are important issues for today's power sector. To inform capacity expansion decisions, hybrid life cycle assessment is used to evaluate a reference design of a parabolic trough concentrating solar power (CSP) facility located in Daggett, CA, along four sustainability metrics: life cycle (LC) greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). This wet-cooled, 103 MW plant utilizes mined nitrates salts in its two-tank, thermal energy storage (TES) system. Design alternatives of dry-cooling, a thermocline TES, and synthetically derived nitrate salt are evaluated. During its LC, the reference CSP plant is estimated to emit 26 g of CO(2eq) per kWh, consume 4.7 L/kWh of water, and demand 0.40 MJ(eq)/kWh of energy, resulting in an EPBT of approximately 1 year. The dry-cooled alternative is estimated to reduce LC water consumption by 77% but increase LC GHG emissions and CED by 8%. Synthetic nitrate salts may increase LC GHG emissions by 52% compared to mined. Switching from two-tank to thermocline TES configuration reduces LC GHG emissions, most significantly for plants using synthetically derived nitrate salts. CSP can significantly reduce GHG emissions compared to fossil-fueled generation; however, dry-cooling may be required in many locations to minimize water consumption.

  13. Quantifying variability in life cycle greenhouse gas inventories of alternative middle distillate transportation fuels.

    PubMed

    Stratton, Russell W; Wong, Hsin Min; Hileman, James I

    2011-05-15

    The presence of variability in life cycle analysis (LCA) is inherent due to both inexact LCA procedures and variation of numerical inputs. Variability in LCA needs to be clearly distinguished from uncertainty. This paper uses specific examples from the production of diesel and jet fuels from 14 different feedstocks to demonstrate general trends in the types and magnitudes of variability present in life cycle greenhouse gas (LC-GHG) inventories of middle distillate fuels. Sources of variability have been categorized as pathway specific, coproduct usage and allocation, and land use change. The results of this research demonstrate that subjective choices such as coproduct usage and allocation methodology can be more important sources of variability in the LC-GHG inventory of a fuel option than the process and energy use of fuel production. Through the application of a consistent analysis methodology across all fuel options, the influence of these subjective biases is minimized, and the LC-GHG inventories for each feedstock-to-fuel option can be effectively compared and discussed. By considering the types and magnitudes of variability across multiple fuel pathways, it is evident that LCA results should be presented as a range instead of a point value. The policy implications of this are discussed.

  14. Environmental impacts of remediation of a trichloroethene-contaminated site: life cycle assessment of remediation alternatives.

    PubMed

    Lemming, Gitte; Hauschild, Michael Z; Chambon, Julie; Binning, Philip J; Bulle, Cécile; Margni, Manuele; Bjerg, Poul L

    2010-12-01

    The environmental impacts of remediation of a chloroethene-contaminated site were evaluated using life cycle assessment (LCA). The compared remediation options are (i) in situ bioremediation by enhanced reductive dechlorination (ERD), (ii) in situ thermal desorption (ISTD), and (iii) excavation of the contaminated soil followed by off-site treatment and disposal. The results showed that choosing the ERD option will reduce the life-cycle impacts of remediation remarkably compared to choosing either ISTD or excavation, which are more energy-demanding. In addition to the secondary impacts of remediation, this study includes assessment of local toxic impacts (the primary impact) related to the on-site contaminant leaching to groundwater and subsequent human exposure via drinking water. The primary human toxic impacts were high for ERD due to the formation and leaching of chlorinated degradation products, especially vinyl chloride during remediation. However, the secondary human toxic impacts of ISTD and excavation are likely to be even higher, particularly due to upstream impacts from steel production. The newly launched model, USEtox, was applied for characterization of primary and secondary toxic impacts and combined with a site-dependent fate model of the leaching of chlorinated ethenes from the fractured clay till site.

  15. Life cycle assessment of a power tower concentrating solar plant and the impacts of key design alternatives.

    PubMed

    Whitaker, Michael B; Heath, Garvin A; Burkhardt, John J; Turchi, Craig S

    2013-06-01

    A hybrid life cycle assessment (LCA) is used to evaluate four sustainability metrics over the life cycle of a power tower concentrating solar power (CSP) facility: greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). The reference design is for a dry-cooled, 106 MW(net) power tower facility located near Tucson, AZ that uses a mixture of mined nitrate salts as the heat transfer fluid and storage medium, a two-tank thermal energy storage system designed for six hours of full load-equivalent storage, and receives auxiliary power from the local electric grid. A thermocline-based storage system, synthetically derived salts, and natural gas auxiliary power are evaluated as design alternatives. Over its life cycle, the reference plant is estimated to have GHG emissions of 37 g CO2eq/kWh, consume 1.4 L/kWh of water and 0.49 MJ/kWh of energy, and have an EPBT of 15 months. Using synthetic salts is estimated to increase GHG emissions by 12%, CED by 7%, and water consumption by 4% compared to mined salts. Natural gas auxiliary power results in greater than 10% decreases in GHG emissions, water consumption, and CED. The thermocline design is most advantageous when coupled with the use of synthetic salts.

  16. Effect of root canal preparation, type of endodontic post and mechanical cycling on root fracture strength

    PubMed Central

    RIPPE, Marília Pivetta; SANTINI, Manuela Favarin; BIER, Carlos Alexandre Souza; BALDISSARA, Paolo; VALANDRO, Luiz Felipe

    2014-01-01

    Objective To evaluate the impact of the type of root canal preparation, intraradicular post and mechanical cycling on the fracture strength of roots. Material and Methods eighty human single rooted teeth were divided into 8 groups according to the instruments used for root canal preparation (manual or rotary instruments), the type of intraradicular post (fiber posts- FRC and cast post and core- CPC) and the use of mechanical cycling (MC) as follows: Manual and FRC; Manual, FRC and MC; Manual and CPC; Manual, CPC and MC; Rotary and FRC; Rotary, FRC and MC; Rotary and CPC; Rotary, CPC and MC. The filling was performed by lateral compactation. All root canals were prepared for a post with a 10 mm length, using the custom #2 bur of the glass fiber post system. For mechanical cycling, the protocol was applied as follows: an angle of incidence of 45°, 37°C, 88 N, 4 Hz, 2 million pulses. All groups were submitted to fracture strength test in a 45° device with 1 mm/ min cross-head speed until failure occurred. Results The 3-way ANOVA showed that the root canal preparation strategy (p<0.03) and post type (p<0.0001) affected the fracture strength results, while mechanical cycling (p=0.29) did not. Conclusion The root canal preparation strategy only influenced the root fracture strength when restoring with a fiber post and mechanical cycling, so it does not seem to be an important factor in this scenario. PMID:25025556

  17. Experimental evolution of an alternating uni- and multicellular life cycle in Chlamydomonas reinhardtii

    PubMed Central

    Ratcliff, William C.; Herron, Matthew D.; Howell, Kathryn; Pentz, Jennifer T.; Rosenzweig, Frank; Travisano, Michael

    2013-01-01

    The transition to multicellularity enabled the evolution of large, complex organisms, but early steps in this transition remain poorly understood. Here we show that multicellular complexity, including development from a single cell, can evolve rapidly in a unicellular organism that has never had a multicellular ancestor. We subject the alga Chlamydomonas reinhardtii to conditions that favour multicellularity, resulting in the evolution of a multicellular life cycle in which clusters reproduce via motile unicellular propagules. While a single-cell genetic bottleneck during ontogeny is widely regarded as an adaptation to limit among-cell conflict, its appearance very early in this transition suggests that it did not evolve for this purpose. Instead, we find that unicellular propagules are adaptive even in the absence of intercellular conflict, maximizing cluster-level fecundity. These results demonstrate that the unicellular bottleneck, a trait essential for evolving multicellular complexity, can arise rapidly via co-option of the ancestral unicellular form. PMID:24193369

  18. A deep-seated mechanism for cycle-dependent sunspot group tilt angles

    NASA Astrophysics Data System (ADS)

    Isik, Emre

    2016-07-01

    The cycle-averaged tilt angle of sunspot groups is an important quantity in determining the magnetic flux diffusing across the equator, which is highly correlated with the strength of the next cycle. This quantity has recently been reported to be anti-correlated with the strength of the solar cycle. I suggest that a deep-seated thermodynamic cycle can be responsible for the observed correlation. Motivated by helioseismic indications, I calculate the effect of cooling of the convective overshoot region on the stability and dynamics of thin, unstable flux tubes. I find that only 5-20 K of cooling in the layer can explain the observed range of tilt angle fluctuations among different cycles. This mechanism can play a role in the nonlinear saturation and amplitude fluctuations of the solar dynamo.

  19. Essential and alternative prey in a ponerine ant: variations according to the colony life cycle.

    PubMed

    Suzzoni, J P; Schatz, B; Dejean, A

    2000-11-01

    We studied the prey specialization of Plectroctena minor, a ponerine ant known to capture mostly millipedes. We compared the prey spectrum of the hunting workers from large colonies with that of the founding queens. The hunting workers captured all kinds of tested prey, but hunted mostly millipedes. Founding queens, which avoided relatively large prey, including the millipedes tested, captured mostly isopods under experimental conditions. We also verified that the presence of millipedes in the diet of the larvae of large colonies was necessary for the production of winged females and strongly enhanced the production of workers, permitting us to assert that P. minor is a predatory species specialized in the capture of millipedes. In contrast, the presence of millipedes had no impact on the production of males. We thus assert that millipedes constitute the 'essential prey' of P. minor, while other arthropod taxa are therefore 'alternative prey'. PMID:11144023

  20. Sleep and alertness during alternating monophasic and polyphasic rest-activity cycles.

    PubMed

    Porcú, S; Casagrande, M; Ferrara, M; Bellatreccia, A

    1998-07-01

    People involved in shift work often have to face altered patterns of sleep and wakefulness. This is particularly true for schedules involving night shifts and/or fragmentation of duty periods throughout the 24-hr day. In such conditions, it can be difficult to obtain satisfactory periods of sleep, and sleepiness on duty is a frequent and dangerous occurrence. The aim of this study was to evaluate sleep and wakefulness periods of subjects whose work schedule was characterized by an alternation of 2 hours of activity and 4 hours of rest (sleep allowed), repeated 4 times throughout the 24-hr day. This schedule was alternated with 24 hours off duty. Nine healthy male volunteers were monitored by means of ambulatory polysomnography while attending their 24-hr rest-activity schedule. Sleep periods were visually scored according to standard criteria. Wake periods were visually scored using both 30 s and 5 s epochs in order to reveal episodes of drowsiness and/or microsleep. Results showed that total sleep time was substantially reduced as compared to the usual 7-8 hour monophasic nocturnal sleep. Subjects did not sleep during the first rest period (11.00-15.00). Time in sleep linearly increased in the course of the 3 remaining rest periods. Normal sleep stage distribution was substantially spared only in the last rest period (3.00-7.00 a.m.). With regard to duty periods, only a few microsleeps were detected and their number did not significantly vary across the four 2-hr activity periods. In conclusion, this rest-activity schedule, despite the considerable sleep reduction, allowed maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps. Whether future research will prove that this regimen does not cause an impairment of performance, it should be a suitable strategy for the management of continuous operations. PMID:9845015

  1. Sleep and alertness during alternating monophasic and polyphasic rest-activity cycles.

    PubMed

    Porcú, S; Casagrande, M; Ferrara, M; Bellatreccia, A

    1998-07-01

    People involved in shift work often have to face altered patterns of sleep and wakefulness. This is particularly true for schedules involving night shifts and/or fragmentation of duty periods throughout the 24-hr day. In such conditions, it can be difficult to obtain satisfactory periods of sleep, and sleepiness on duty is a frequent and dangerous occurrence. The aim of this study was to evaluate sleep and wakefulness periods of subjects whose work schedule was characterized by an alternation of 2 hours of activity and 4 hours of rest (sleep allowed), repeated 4 times throughout the 24-hr day. This schedule was alternated with 24 hours off duty. Nine healthy male volunteers were monitored by means of ambulatory polysomnography while attending their 24-hr rest-activity schedule. Sleep periods were visually scored according to standard criteria. Wake periods were visually scored using both 30 s and 5 s epochs in order to reveal episodes of drowsiness and/or microsleep. Results showed that total sleep time was substantially reduced as compared to the usual 7-8 hour monophasic nocturnal sleep. Subjects did not sleep during the first rest period (11.00-15.00). Time in sleep linearly increased in the course of the 3 remaining rest periods. Normal sleep stage distribution was substantially spared only in the last rest period (3.00-7.00 a.m.). With regard to duty periods, only a few microsleeps were detected and their number did not significantly vary across the four 2-hr activity periods. In conclusion, this rest-activity schedule, despite the considerable sleep reduction, allowed maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps. Whether future research will prove that this regimen does not cause an impairment of performance, it should be a suitable strategy for the management of continuous operations.

  2. CYCLE pilot: a protocol for a pilot randomised study of early cycle ergometry versus routine physiotherapy in mechanically ventilated patients

    PubMed Central

    Molloy, Alexander J; Clarke, France; Herridge, Margaret S; Koo, Karen K Y; Rudkowski, Jill; Seely, Andrew J E; Pellizzari, Joseph R; Tarride, Jean-Eric; Mourtzakis, Marina; Karachi, Timothy; Cook, Deborah J

    2016-01-01

    Introduction Early exercise with in-bed cycling as part of an intensive care unit (ICU) rehabilitation programme has the potential to improve physical and functional outcomes following critical illness. The objective of this study is to determine the feasibility of enrolling adults in a multicentre pilot randomised clinical trial (RCT) of early in-bed cycling versus routine physiotherapy to inform a larger RCT. Methods and analysis 60-patient parallel group pilot RCT in 7 Canadian medical-surgical ICUs. We will include all previously ambulatory adult patients within the first 0–4 days of mechanical ventilation, without exclusion criteria. After informed consent, patients will be randomised using a web-based, centralised electronic system, to 30 min of in-bed leg cycling in addition to routine physiotherapy, 5 days per week, for the duration of their ICU stay (28 days maximum) or routine physiotherapy alone. We will measure patients' muscle strength (Medical Research Council Sum Score, quadriceps force) and function (Physical Function in ICU Test (scored), 30 s sit-to-stand, 2 min walk test) at ICU awakening, ICU discharge and hospital discharge. Our 4 feasibility outcomes are: (1) patient accrual of 1–2 patients per month per centre, (2) protocol violation rate <20%, (3) outcome measure ascertainment >80% at the 3 time points and (4) blinded outcomes ascertainment >80% at hospital discharge. Hospital outcome assessors are blinded to group assignment, whereas participants, ICU physiotherapists, ICU caregivers, research coordinators and ICU outcome assessors are not blinded to group assignment. We will analyse feasibility outcomes with descriptive statistics. Ethics and dissemination Each participating centre will obtain local ethics approval, and results of the study will be published to inform the design and conduct of a future multicentre RCT of in-bed cycling to improve physical outcomes in ICU survivors. Trial registration number NCT02377830; Pre

  3. Evaluation of different end-of-life management alternatives for used natural cork stoppers through life cycle assessment.

    PubMed

    Demertzi, Martha; Dias, Ana Cláudia; Matos, Arlindo; Arroja, Luís Manuel

    2015-12-01

    An important aspect of sustainable development is the implementation of effective and sustainable waste management strategies. The present study focuses on a Life Cycle Assessment (LCA) approach to different waste management strategies for natural cork stoppers, namely incineration at a municipal solid waste incinerator, landfilling in a sanitary landfill, and recycling. In the literature, there are no LCA studies analyzing in detail the end-of-life stage of natural cork stoppers as well as other cork products. In addition, cork is usually treated as wood at the end-of-life stage. Thus, the outcome of this study can provide an important insight into this matter. The results showed that different management alternatives, namely incineration and recycling, could be chosen depending on the impact category considered. The former alternative presented the best environmental results in the impact categories of climate change, ozone depletion and acidification, while the latter for photochemical ozone formation and mineral and fossil resource depletion. The landfilling alternative did not present the best environmental performance in any of the impact categories. However, when the biogenic carbon dioxide emission was assessed for the climate change category, the landfilling alternative was found to be the most effective since most of the biogenic carbon would be permanently stored in the cork products and not emitted into the atmosphere. A sensitivity analysis was performed and the results showed that there are various parameters that can significantly influence the results (e.g., carbon content in cork and decay rate of cork in the landfill). Thus, LCA studies should include a detailed description concerning their assumptions when the end-of-life stage is included in the boundaries since they can influence the results, and furthermore, to facilitate the comparison of different end-of-life scenarios. The present study and the obtained results could be useful for the

  4. Evaluation of different end-of-life management alternatives for used natural cork stoppers through life cycle assessment.

    PubMed

    Demertzi, Martha; Dias, Ana Cláudia; Matos, Arlindo; Arroja, Luís Manuel

    2015-12-01

    An important aspect of sustainable development is the implementation of effective and sustainable waste management strategies. The present study focuses on a Life Cycle Assessment (LCA) approach to different waste management strategies for natural cork stoppers, namely incineration at a municipal solid waste incinerator, landfilling in a sanitary landfill, and recycling. In the literature, there are no LCA studies analyzing in detail the end-of-life stage of natural cork stoppers as well as other cork products. In addition, cork is usually treated as wood at the end-of-life stage. Thus, the outcome of this study can provide an important insight into this matter. The results showed that different management alternatives, namely incineration and recycling, could be chosen depending on the impact category considered. The former alternative presented the best environmental results in the impact categories of climate change, ozone depletion and acidification, while the latter for photochemical ozone formation and mineral and fossil resource depletion. The landfilling alternative did not present the best environmental performance in any of the impact categories. However, when the biogenic carbon dioxide emission was assessed for the climate change category, the landfilling alternative was found to be the most effective since most of the biogenic carbon would be permanently stored in the cork products and not emitted into the atmosphere. A sensitivity analysis was performed and the results showed that there are various parameters that can significantly influence the results (e.g., carbon content in cork and decay rate of cork in the landfill). Thus, LCA studies should include a detailed description concerning their assumptions when the end-of-life stage is included in the boundaries since they can influence the results, and furthermore, to facilitate the comparison of different end-of-life scenarios. The present study and the obtained results could be useful for the

  5. Generation of spatially periodic patterns by a mechanical instability: a mechanical alternative to the Turing model.

    PubMed

    Harris, A K; Stopak, D; Warner, P

    1984-04-01

    We have studied the generation of spatial patterns created by mechanical (rather than chemical) instabilities. When dissociated fibroblasts are suspended in a gel of reprecipitated collagen, and the contraction of the gel as a whole is physically restrained by attachment of its margin to a glass fibre meshwork, then the effect of the fibroblasts' traction is to break up the cell-matrix mixture into a series of clumps or aggregations of cells and compressed matrix. These aggregations are interconnected by linear tracts of collagen fibres aligned under the tensile stress exerted by fibroblast traction. The patterns generated by this mechanical instability vary depending upon cell population density and other factors. Over a certain range of cell concentrations, this mechanical instability yields geometric patterns which resemble but are usually much less regular than the patterns which develop normally in the dermis of developing bird skin. We propose that an equivalent mechanical instability, occurring during the embryonic development of this skin, could be the cause not only of the clumping of dermal fibroblasts to form the feather papillae, but also of the alignment of collagen fibres into the characteristic polygonal network of fibre bundles - which interconnect these papillae and which presage the subsequent pattern of the dermal muscles serving to control feather movements. More generally, we suggest that this type of mechanical instability can serve the morphogenetic functions for which Turing's chemical instability and other reaction-diffusion systems have been proposed. Mechanical instabilities can create physical structures directly, in one step, in contrast to the two or more steps which would be required if positional information first had to be specified by chemical gradients and then only secondarily implemented in physical form. In addition, physical forces can act more quickly and at much longer range than can diffusing chemicals and can generate a

  6. Cycle training induces muscle hypertrophy and strength gain: strategies and mechanisms.

    PubMed

    Ozaki, Hayao; Loenneke, J P; Thiebaud, R S; Abe, T

    2015-03-01

    Cycle training is widely performed as a major part of any exercise program seeking to improve aerobic capacity and cardiovascular health. However, the effect of cycle training on muscle size and strength gain still requires further insight, even though it is known that professional cyclists display larger muscle size compared to controls. Therefore, the purpose of this review is to discuss the effects of cycle training on muscle size and strength of the lower extremity and the possible mechanisms for increasing muscle size with cycle training. It is plausible that cycle training requires a longer period to significantly increase muscle size compared to typical resistance training due to a much slower hypertrophy rate. Cycle training induces muscle hypertrophy similarly between young and older age groups, while strength gain seems to favor older adults, which suggests that the probability for improving in muscle quality appears to be higher in older adults compared to young adults. For young adults, higher-intensity intermittent cycling may be required to achieve strength gains. It also appears that muscle hypertrophy induced by cycle training results from the positive changes in muscle protein net balance.

  7. The Primary and Secondary Production of Germanium: A Life-Cycle Assessment of Different Process Alternatives

    NASA Astrophysics Data System (ADS)

    Robertz, Benedicte; Verhelle, Jensen; Schurmans, Maarten

    2015-02-01

    Germanium is a semiconducting metalloid element used in optical fibers, catalysis, infrared optics, solar cells, and light-emitting diodes. The need for Ge in these markets is considered to increase by a steady ~1% on a yearly basis. Its economic importance, coupled with the identified supply risks, has led to the classification of germanium as a critical raw material within Europe. Since the early 1950s, Umicore Electro-Optic Materials has supplied germanium-based materials solutions to its markets around the world. Umicore extracts germanium from a wide range of refining and recycling feeds. The main objectives of this study were to quantify the potential environmental impacts of the production of germanium from production scraps from the photovoltaic industry and to compare them with the potential impacts of the primary production of germanium from coal. The data related to the secondary production are Umicore-specific data. Environmental impact scores have been calculated for the impact categories recommended by the International reference life cycle data system. The comparison of the primary and secondary production highlights the benefit linked to the recycling of metals.

  8. Alternative "global warming" metrics in life cycle assessment: a case study with existing transportation data.

    PubMed

    Peters, Glen P; Aamaas, Borgar; T Lund, Marianne; Solli, Christian; Fuglestvedt, Jan S

    2011-10-15

    The Life Cycle Assessment (LCA) impact category "global warming" compares emissions of long-lived greenhouse gases (LLGHGs) using Global Warming Potential (GWP) with a 100-year time-horizon as specified in the Kyoto Protocol. Two weaknesses of this approach are (1) the exclusion of short-lived climate forcers (SLCFs) and biophysical factors despite their established importance, and (2) the use of a particular emission metric (GWP) with a choice of specific time-horizons (20, 100, and 500 years). The GWP and the three time-horizons were based on an illustrative example with value judgments and vague interpretations. Here we illustrate, using LCA data of the transportation sector, the importance of SLCFs relative to LLGHGs, different emission metrics, and different treatments of time. We find that both the inclusion of SLCFs and the choice of emission metric can alter results and thereby change mitigation priorities. The explicit inclusion of time, both for emissions and impacts, can remove value-laden assumptions and provide additional information for impact assessments. We believe that our results show that a debate is needed in the LCA community on the impact category "global warming" covering which emissions to include, the emission metric(s) to use, and the treatment of time. PMID:21936535

  9. Alternative "global warming" metrics in life cycle assessment: a case study with existing transportation data.

    PubMed

    Peters, Glen P; Aamaas, Borgar; T Lund, Marianne; Solli, Christian; Fuglestvedt, Jan S

    2011-10-15

    The Life Cycle Assessment (LCA) impact category "global warming" compares emissions of long-lived greenhouse gases (LLGHGs) using Global Warming Potential (GWP) with a 100-year time-horizon as specified in the Kyoto Protocol. Two weaknesses of this approach are (1) the exclusion of short-lived climate forcers (SLCFs) and biophysical factors despite their established importance, and (2) the use of a particular emission metric (GWP) with a choice of specific time-horizons (20, 100, and 500 years). The GWP and the three time-horizons were based on an illustrative example with value judgments and vague interpretations. Here we illustrate, using LCA data of the transportation sector, the importance of SLCFs relative to LLGHGs, different emission metrics, and different treatments of time. We find that both the inclusion of SLCFs and the choice of emission metric can alter results and thereby change mitigation priorities. The explicit inclusion of time, both for emissions and impacts, can remove value-laden assumptions and provide additional information for impact assessments. We believe that our results show that a debate is needed in the LCA community on the impact category "global warming" covering which emissions to include, the emission metric(s) to use, and the treatment of time.

  10. Muscular tissues of the squid Doryteuthis pealeii express identical myosin heavy chain isoforms: an alternative mechanism for tuning contractile speed.

    PubMed

    Shaffer, Justin F; Kier, William M

    2012-01-15

    The speed of muscle contraction is largely controlled at the sarcomere level by the ATPase activity of the motor protein myosin. Differences in amino acid sequence in catalytically important regions of myosin yield different myosin isoforms with varying ATPase activities and resulting differences in cross-bridge cycling rates and interfilamentary sliding velocities. Modulation of whole-muscle performance by changes in myosin isoform ATPase activity is regarded as a universal mechanism to tune contractile properties, especially in vertebrate muscles. Invertebrates such as squid, however, may exhibit an alternative mechanism to tune contractile properties that is based on differences in muscle ultrastructure, including variable myofilament and sarcomere lengths. To determine definitively whether contractile properties of squid muscles are regulated via different myosin isoforms (i.e. different ATPase activities), the nucleotide and amino acid sequences of the myosin heavy chain from the squid Doryteuthis pealeii were determined from the mantle, arm, tentacle, fin and funnel retractor musculature. We identified three myosin heavy chain isoforms in squid muscular tissues, with differences arising at surface loop 1 and the carboxy terminus. All three isoforms were detected in all five tissues studied. These results suggest that the muscular tissues of D. pealeii express identical myosin isoforms, and it is likely that differences in muscle ultrastructure, not myosin ATPase activity, represent the most important mechanism for tuning contractile speeds.

  11. Ceramic Inlays: Effect of Mechanical Cycling and Ceramic Type on Restoration-dentin Bond Strength.

    PubMed

    Trindade, F Z; Kleverlaan, C J; da Silva, L H; Feilzer, A J; Cesar, P F; Bottino, M A; Valandro, L F

    2016-01-01

    This study aimed to evaluate the bond strength between dentin and five different ceramic inlays in permanent maxillary premolars, with and without mechanical cycling. One hundred permanent maxillary premolars were prepared and divided into 10 groups (n=10) according to the ceramic system (IPS e.Max Press; IPS e.Max CAD; Vita PM9; Vita Mark II; and Vita VM7) and the mechanical cycling factor (with and without [100 N, 2 Hz, 1.2×10(6) cycles]). The inlays were adhesively cemented, and all of the specimens were cut into microbars (1×1 mm, nontrimming method), which were tested under microtensile loading. The failure mode was classified and contact angle, roughness, and microtopographic analyses were performed on each ceramic surface. The mechanical cycling had a significant effect (p=0.0087) on the bond strength between dentin and IPS e.max Press. The Vita Mark II group had the highest bond strength values under both conditions, with mechanical cycling (9.7±1.8 MPa) and without (8.2±1.9 MPa), while IPS e.Max CAD had the lowest values (2.6±1.6 and 2.2±1.4, respectively). The adhesive failure mode at the ceramic/cement interface was the most frequent. Vita Mark II showed the highest value of average roughness. IPS e.max Press and Vita Mark II ceramics presented the lowest contact angles. In conclusion, the composition and manufacturing process of ceramics seem to have an influence on the ceramic surface and resin cement bond strength. Mechanical cycling did not cause significant degradation on the dentin and ceramic bond strength under the configuration used. PMID:27455117

  12. Structures of yeast mitochondrial ADP/ATP carriers support a domain-based alternating-access transport mechanism.

    PubMed

    Ruprecht, Jonathan J; Hellawell, Alex M; Harding, Marilyn; Crichton, Paul G; McCoy, Airlie J; Kunji, Edmund R S

    2014-01-28

    The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix. The carrier cycles by an unresolved mechanism between the cytoplasmic state, in which the carrier accepts ADP from the cytoplasm, and the matrix state, in which it accepts ATP from the mitochondrial matrix. Here we present the structures of the yeast ADP/ATP carriers Aac2p and Aac3p in the cytoplasmic state. The carriers have three domains and are closed at the matrix side by three interdomain salt-bridge interactions, one of which is braced by a glutamine residue. Glutamine braces are conserved in mitochondrial carriers and contribute to an energy barrier, preventing the conversion to the matrix state unless substrate binding occurs. At the cytoplasmic side a second salt-bridge network forms during the transport cycle, as demonstrated by functional analysis of mutants with charge-reversed networks. Analyses of the domain structures and properties of the interdomain interfaces indicate that interconversion between states involves movement of the even-numbered α-helices across the surfaces of the odd-numbered α-helices by rotation of the domains. The odd-numbered α-helices have an L-shape, with proline or serine residues at the kinks, which functions as a lever-arm, coupling the substrate-induced disruption of the matrix network to the formation of the cytoplasmic network. The simultaneous movement of three domains around a central translocation pathway constitutes a unique mechanism among transport proteins. These findings provide a structural description of transport by mitochondrial carrier proteins, consistent with an alternating-access mechanism.

  13. Comparative alternative materials assessment to screen toxicity hazards in the life cycle of CIGS thin film photovoltaics.

    PubMed

    Eisenberg, Daniel A; Yu, Mengjing; Lam, Carl W; Ogunseitan, Oladele A; Schoenung, Julie M

    2013-09-15

    Copper-indium-gallium-selenium-sulfide (CIGS) thin film photovoltaics are increasingly penetrating the market supply for consumer solar panels. Although CIGS is attractive for producing less greenhouse gas emissions than fossil-fuel based energy sources, CIGS manufacturing processes and solar cell devices use hazardous materials that should be carefully considered in evaluating and comparing net environmental benefits of energy products. Through this research, we present a case study on the toxicity hazards associated with alternative materials selection for CIGS manufacturing. We applied two numeric models, The Green Screen for Safer Chemicals and the Toxic Potential Indicator. To improve the sensitivity of the model outputs, we developed a novel, life cycle thinking based hazard assessment method that facilitates the projection of hazards throughout material life cycles. Our results show that the least hazardous CIGS solar cell device and manufacturing protocol consist of a titanium substrate, molybdenum metal back electrode, CuInS₂ p-type absorber deposited by spray pyrolysis, ZnS buffer deposited by spray ion layer gas reduction, ZnO:Ga transparent conducting oxide (TCO) deposited by sputtering, and the encapsulant polydimethylsiloxane.

  14. Identification of Wilms' tumor 1-associating protein complex and its role in alternative splicing and the cell cycle.

    PubMed

    Horiuchi, Keiko; Kawamura, Takeshi; Iwanari, Hiroko; Ohashi, Riuko; Naito, Makoto; Kodama, Tatsuhiko; Hamakubo, Takao

    2013-11-15

    Wilms' tumor 1-associating protein (WTAP) is a putative splicing regulator that is thought to be required for cell cycle progression through the stabilization of cyclin A2 mRNA and mammalian early embryo development. To further understand how WTAP acts in the context of the cellular machinery, we identified its interacting proteins in human umbilical vein endothelial cells and HeLa cells using shotgun proteomics. Here we show that WTAP forms a novel protein complex including Hakai, Virilizer homolog, KIAA0853, RBM15, the arginine/serine-rich domain-containing proteins BCLAF1 and THRAP3, and certain general splicing regulators, most of which have reported roles in post-transcriptional regulation. The depletion of these respective components of the complex resulted in reduced cell proliferation along with G2/M accumulation. Double knockdown of the serine/arginine-rich (SR)-like proteins BCLAF1 and THRAP3 by siRNA resulted in a decrease in the nuclear speckle localization of WTAP, whereas the nuclear speckles were intact. Furthermore, we found that the WTAP complex regulates alternative splicing of the WTAP pre-mRNA by promoting the production of a truncated isoform, leading to a change in WTAP protein expression. Collectively, these findings show that the WTAP complex is a novel component of the RNA processing machinery, implying an important role in both posttranscriptional control and cell cycle regulation. PMID:24100041

  15. Comparative alternative materials assessment to screen toxicity hazards in the life cycle of CIGS thin film photovoltaics.

    PubMed

    Eisenberg, Daniel A; Yu, Mengjing; Lam, Carl W; Ogunseitan, Oladele A; Schoenung, Julie M

    2013-09-15

    Copper-indium-gallium-selenium-sulfide (CIGS) thin film photovoltaics are increasingly penetrating the market supply for consumer solar panels. Although CIGS is attractive for producing less greenhouse gas emissions than fossil-fuel based energy sources, CIGS manufacturing processes and solar cell devices use hazardous materials that should be carefully considered in evaluating and comparing net environmental benefits of energy products. Through this research, we present a case study on the toxicity hazards associated with alternative materials selection for CIGS manufacturing. We applied two numeric models, The Green Screen for Safer Chemicals and the Toxic Potential Indicator. To improve the sensitivity of the model outputs, we developed a novel, life cycle thinking based hazard assessment method that facilitates the projection of hazards throughout material life cycles. Our results show that the least hazardous CIGS solar cell device and manufacturing protocol consist of a titanium substrate, molybdenum metal back electrode, CuInS₂ p-type absorber deposited by spray pyrolysis, ZnS buffer deposited by spray ion layer gas reduction, ZnO:Ga transparent conducting oxide (TCO) deposited by sputtering, and the encapsulant polydimethylsiloxane. PMID:23811631

  16. Strategic Grassland Bird Conservation throughout the annual cycle: Linking policy alternatives, landowner decisions, and biological population outcomes

    USGS Publications Warehouse

    Drum, Ryan G.; Ribic, Christine; Koch, Katie; Lonsdorf, Eric V.; Grant, Edward C.; Ahlering, Marissa; Barnhill, Laurel; Dailey, Thomas; Lor, Socheata; Mueller, Connie; Pavlacky, D.C.; Rideout, Catherine; Sample, David W.

    2015-01-01

    Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.

  17. Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives, Landowner Decisions, and Biological Population Outcomes

    PubMed Central

    Drum, Ryan G.; Ribic, Christine A.; Koch, Katie; Lonsdorf, Eric; Grant, Evan; Ahlering, Marissa; Barnhill, Laurel; Dailey, Thomas; Lor, Socheata; Mueller, Connie; Pavlacky, David C.; Rideout, Catherine; Sample, David

    2015-01-01

    Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds. PMID:26569108

  18. Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives, Landowner Decisions, and Biological Population Outcomes.

    PubMed

    Drum, Ryan G; Ribic, Christine A; Koch, Katie; Lonsdorf, Eric; Grant, Evan; Ahlering, Marissa; Barnhill, Laurel; Dailey, Thomas; Lor, Socheata; Mueller, Connie; Pavlacky, David C; Rideout, Catherine; Sample, David

    2015-01-01

    Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds. PMID:26569108

  19. Hybrid life-cycle assessment (LCA) of CO2 emission with management alternatives for household food wastes in Japan.

    PubMed

    Inaba, Rokuta; Nansai, Keisuke; Fujii, Minoru; Hashimoto, Seiji

    2010-06-01

    In this study, we conducted a hybrid life-cycle assessment (LCA) to evaluate reductions in CO(2) emissions by food waste biogasification of household food wastes in Japan. Two alternative scenarios were examined. In one alternative (Ref), all combustible municipal solid wastes (MSWs), including food waste, are incinerated. In the other (Bio), food waste is biogasified, while the other combustible wastes are incinerated. An inventory analysis of energy and material flow in the MSW management system was conducted. Subsequently, the inventory data were summarized into an input-output format, and a make-use input-output framework was applied. Furthermore, a production equilibrium model was established using a matrix representing the input- output relationship of energy and materials among the processes and sectors. Several levels of power generation efficiency from incineration were applied as a sensitivity analysis. The hybrid LCA indicated that the difference between the Bio and Ref scenarios, from the perspective of CO( 2) emissions, is relatively small. However, a 13-14% reduction of CO(2) emissions of the total waste management sector in Japan may be achieved by improving the efficiency of power generation from incineration from 10% to 25%.

  20. Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives, Landowner Decisions, and Biological Population Outcomes.

    PubMed

    Drum, Ryan G; Ribic, Christine A; Koch, Katie; Lonsdorf, Eric; Grant, Evan; Ahlering, Marissa; Barnhill, Laurel; Dailey, Thomas; Lor, Socheata; Mueller, Connie; Pavlacky, David C; Rideout, Catherine; Sample, David

    2015-01-01

    Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.

  1. Hybrid life-cycle assessment (LCA) of CO2 emission with management alternatives for household food wastes in Japan.

    PubMed

    Inaba, Rokuta; Nansai, Keisuke; Fujii, Minoru; Hashimoto, Seiji

    2010-06-01

    In this study, we conducted a hybrid life-cycle assessment (LCA) to evaluate reductions in CO(2) emissions by food waste biogasification of household food wastes in Japan. Two alternative scenarios were examined. In one alternative (Ref), all combustible municipal solid wastes (MSWs), including food waste, are incinerated. In the other (Bio), food waste is biogasified, while the other combustible wastes are incinerated. An inventory analysis of energy and material flow in the MSW management system was conducted. Subsequently, the inventory data were summarized into an input-output format, and a make-use input-output framework was applied. Furthermore, a production equilibrium model was established using a matrix representing the input- output relationship of energy and materials among the processes and sectors. Several levels of power generation efficiency from incineration were applied as a sensitivity analysis. The hybrid LCA indicated that the difference between the Bio and Ref scenarios, from the perspective of CO( 2) emissions, is relatively small. However, a 13-14% reduction of CO(2) emissions of the total waste management sector in Japan may be achieved by improving the efficiency of power generation from incineration from 10% to 25%. PMID:19942648

  2. [Effects of biochar on soil nitrogen cycle and related mechanisms: a review].

    PubMed

    Pan, Yi-Fan; Yang, Min; Dong, Da; Wu, Wei-Xiang

    2013-09-01

    Biochar has its unique physical and chemical properties, playing a significant role in soil amelioration, nutrient retention, fertility improvement, and carbon storage, and being a hotspot in the research areas of soil ecosystem, biogeochemical cycling, and agricultural carbon sequestration. As a kind of anthropogenic materials, biochar has the potential in controlling soil nitrogen (N) cycle directly or indirectly, and thus, has profound effects on soil ecological functions. This paper reviewed the latest literatures regarding the effects of biochar applications on soil N cycle, with the focuses on the nitrogen species adsorption and the biochemical processes (nitrification, denitrification, and nitrogen fixation) , and analyzed the related action mechanisms of biochar. The future research areas for better understanding the interactions between biochar and soil N cycle were proposed.

  3. Cycling stability and degradation mechanism of LiMnPO4 based electrodes

    NASA Astrophysics Data System (ADS)

    Moskon, J.; Pivko, M.; Jerman, I.; Tchernychova, E.; Logar, N. Zabukovec; Zorko, M.; Selih, V. S.; Dominko, R.; Gaberscek, M.

    2016-01-01

    Long term stability of LiMnPO4 particles with a crystallite size between ˜20 and 50 nm covered with a dense native carbon coating (14 wt.%) is demonstrated. More than 500 cycles at a rate of C/20, in the potential window of 2.7-4.5 V and a temperature of 55 °C were achieved. During most of the cycling the average capacity decay was less than 0.06% per cycle. After about 500 cycles a sudden capacity drop was observed. Degradation processes in various stages of cycling were thoroughly examined using a range of techniques. Severe surface film formation, manganese dissolution and degradation of LixMnPO4 accompanied by formation of Li4P2O7 were clearly identified. The good long term stability seems to be due to dense, protective carbon coating. Decomposition is most likely initiated at local defects in the microstructure of pyrolytic carbon coating around LiMnPO4 particles. In addition to known degradation mechanisms of LiMnPO4 we observed pronounced gradual amorphization of the olivine crystallites during long-term cycling at 55 °C. Finally, changes in morphology of the carbon black additive after prolonged cycling are reported and commented.

  4. Parametric Studies Of Failure Mechanisms In Thermal Barrier Coatings During Thermal Cycling Using FEM

    NASA Astrophysics Data System (ADS)

    Srivathsa, B.; Das, D. K.

    2015-12-01

    Thermal barrier coatings (TBCs) are widely used on different hot components of gas turbine engines such as blades and vanes. Although, several mechanisms for the failure of the TBCs have been suggested, it is largely accepted that the durability of these coatings is primarily determined by the residual stresses that are developed during the thermal cycling. In the present study, the residual stress build-up in an electron beam physical vapour deposition (EB-PVD) based TBCs on a coupon during thermal cycling has been studied by varying three parameters such as the cooling rate, TBC thickness and substrate thickness. A two-dimensional thermomechanical generalized plane strain finite element simulations have been performed for thousand cycles. It was observed that these variations change the stress profile significantly and the stress severity factor increases non-linearly. Overall, the predictions of the model agree with reported experimental results and help in predicting the failure mechanisms.

  5. Fatigue responses of lead zirconate titanate stacks under semibipolar electric cycling with mechanical preload

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Cooper, Thomas A.; Lin, Hua-Tay; Wereszczak, Andrew A.

    2010-10-01

    Lead zirconate titanate (PZT) stacks that had an interdigital internal electrode configuration were tested to more than 108 cycles. A 100 Hz semibipolar sine wave with a field range of +4.5/-0.9 kV/mm was used in cycling with a concurrently-applied 20 MPa preload. Significant reductions in piezoelectric and dielectric responses were observed during the cycling depending on the measuring condition. Extensive partial discharges were also observed. These surface events resulted in the erosion of external electrode and the exposure of internal electrodes. Sections prepared by sequential polishing technique revealed a variety of damage mechanisms including delaminations, pores, and etch grooves. The scale of damage was correlated with the degree of fatigue-induced reduction in piezoelectric and dielectric responses. The results from this study demonstrate the feasibility of using a semibipolar mode to drive a PZT stack under a mechanical preload and illustrate the potential fatigue and damages of the stack in service.

  6. Forward and backward arm cycling are regulated by equivalent neural mechanisms.

    PubMed

    Zehr, E Paul; Hundza, Sandra R

    2005-01-01

    It was shown some time ago that cutaneous reflexes were phase-reversed when comparing forward and backward treadmill walking. Activity of central-pattern-generating networks (CPG) regulating neural activity for locomotion was suggested as a mechanism involved in this "program reversal." We have been investigating the neural control of arm movements and the role for CPG mechanisms in regulating rhythmic arm cycling. The purpose of this study was to evaluate the pattern of muscle activity and reflex modulation when comparing forward and backward arm cycling. During rhythmic arm cycling (forward and backward), cutaneous reflexes were evoked with trains (5 x 1.0 ms pulses at 300 Hz) of electrical stimulation delivered to the superficial radial (SR) nerve at the wrist. Electromyographic (EMG) recordings were made bilaterally from muscles acting at the shoulder, elbow, and wrist. Analysis was conducted on specific sections of the movement cycle after phase-averaging contingent on the timing of stimulation in the movement cycle. EMG patterns for rhythmic arm cycling are similar during both forward and backward motion. Cutaneous reflex amplitudes were similarly modulated at both early and middle latency irrespective of arm cycling direction. That is, at similar phases in the movement cycle, responses of corresponding sign and amplitude were seen regardless of movement direction. The results are generally parallel to the observations seen in leg muscles after stimulation of cutaneous nerves in the foot during forward and backward walking and provide further evidence for CPG activity contributing to neural activation and reflex modulation during rhythmic arm movement.

  7. Effect of surface treatment of brackets and mechanical cycling on adhesion to enamel.

    PubMed

    Arrais, Fabiola Rossato; Degrazia, Felipe; Peres, Bernardo Urbanetto; Ferrazzo, Vilmar Antonio; Grehs, Renesio Armindo; Valandro, Luiz Felipe

    2014-01-01

    This in vitro study sought to evaluate how surface conditioning from bracket and mechanical cycling aging affected the bond strength between metallic brackets and bovine enamel, and to determine the adhesive remnant index. Eighty bovine incisors were embedded in acrylic resin using polyvinyl chloride rings and divided into 4 groups based on surface treatment (n = 20). Group 1 (control) received no surface treatment, Group 2 specimens were sandblasted with aluminum oxide particles, Group 3 specimens were sandblasted with silicon oxide and treated with a tribochemichemical silica coupling agent, and Group 4 specimens were primed with a multidomain protein-based agent. Half of the specimens were submitted to shear bond testing, while the others were subjected to mechanical cycling. ANOVA showed that mechanical cycling did not have a significant influence on bond strength (P = 0.9244), while surface conditioning of the brackets did (P = 0.0001). Tukey's test results were similar for mechanical cycling, and indicated that only Group 3 significantly improved the resin bond to the brackets; however, this group also demonstrated the highest percentage of enamel failure. PMID:24784526

  8. Learning the Cardiac Cycle: Simultaneous Observations of Electrical and Mechanical Events.

    ERIC Educational Resources Information Center

    Kenney, Richard Alec; Frey, Mary Anne Bassett

    1980-01-01

    Described is a method for integrating electrical and mechanical events of the cardiac cycle by measuring systolic time intervals, which involves simultaneous recording of the ECG, a phonocardiogram, and the contour of the carotid pulse. Both resting and stress change data are provided as bases for class discussion. (CS)

  9. 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...

  10. Synaptic plasticity and cell cycle activation in neurons are alternative effector pathways: the 'Dr. Jekyll and Mr. Hyde concept' of Alzheimer's disease or the yin and yang of neuroplasticity.

    PubMed

    Arendt, Thomas

    2003-10-01

    Mental actions are based on the dynamic organization of neuronal networks. In particular, phylogenetically young brain areas (e.g., cortical associative circuits) involved in the realization of higher brain functions are continuously re-adjusted to meet environmental demands. The mechanisms of synaptic plasticity, i.e., of structural stabilization and labilization underlying a life-long synaptic remodelling, are largely based on external morphoregulatory cues and internal signalling pathways that non-neuronal cells have phylogenetically acquired to sense their relationship to the local neighbourhood and to control after development is completed proliferation and differentiation in the process of tissue repair and regeneration. After having withdrawn from the cell cycle, differentiated neurons are, thus, able to use molecular mechanisms primarily developed to control proliferation alternatively to control synaptic plasticity. The existence of these alternative effector pathways within a neuron puts it at risk to erroneously convert signals derived from plastic synaptic changes into positional cues that will activate the cell cycle. This cell cycle activation potentially links synaptic plasticity to cell death. Preventing cell cycle activation by locking neurons in a differentiated but still highly plastic phenotype will, thus, be crucial to prevent neurodegeneration. PMID:14687983

  11. A New Mechanism for Dissipation of Alternating Fields in Poynting-dominated Outflows

    NASA Astrophysics Data System (ADS)

    Lyubarsky, Yuri

    2010-12-01

    Reconnection of alternating magnetic fields is an important energy transformation mechanism in Poynting-dominated outflows. We show that the reconnection is facilitated by the Kruskal-Schwarzschild instability of current sheets separating the oppositely directed fields. This instability, which is a magnetic counterpart of the Rayleigh-Taylor instability, develops if the flow is accelerated. Then the plasma drips out of the current sheet, providing conditions for rapid reconnection. Since the magnetic dissipation leads to the flow acceleration, the process is self-sustaining. In pulsar winds, this process could barely compete with the earlier proposed dissipation mechanisms. However, the novel mechanism turns out to be very efficient at active galactic nucleus and gamma-ray burst conditions.

  12. A NEW MECHANISM FOR DISSIPATION OF ALTERNATING FIELDS IN POYNTING-DOMINATED OUTFLOWS

    SciTech Connect

    Lyubarsky, Yuri

    2010-12-20

    Reconnection of alternating magnetic fields is an important energy transformation mechanism in Poynting-dominated outflows. We show that the reconnection is facilitated by the Kruskal-Schwarzschild instability of current sheets separating the oppositely directed fields. This instability, which is a magnetic counterpart of the Rayleigh-Taylor instability, develops if the flow is accelerated. Then the plasma drips out of the current sheet, providing conditions for rapid reconnection. Since the magnetic dissipation leads to the flow acceleration, the process is self-sustaining. In pulsar winds, this process could barely compete with the earlier proposed dissipation mechanisms. However, the novel mechanism turns out to be very efficient at active galactic nucleus and gamma-ray burst conditions.

  13. A Mechanism for the Loading-Unloading Substorm Cycle Missing in MHD Global Magnetospheric Simulation Models

    NASA Technical Reports Server (NTRS)

    Klimas, A. J.; Uritsky, V.; Vassiliadis, D.; Baker, D. N.

    2005-01-01

    Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading- unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current- driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading- unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval, the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.

  14. Failure mechanisms of nano-silicon anodes upon cycling: an electrode porosity evolution model.

    PubMed

    Radvanyi, Etienne; Porcher, Willy; De Vito, Eric; Montani, Alexandre; Franger, Sylvain; Jouanneau Si Larbi, Séverine

    2014-08-28

    With a specific capacity of 3600 mA h g(-1), silicon is a promising anode active material for Li-ion batteries (LIBs). However, because of the huge volume changes undergone by Si particles upon (de)alloying with lithium, Si electrodes suffer from rapid capacity fading. A deep understanding of the associated failure mechanisms is necessary to improve these electrochemical performances. To reach this goal, we investigate here nano-Si based electrodes by several characterization techniques. Thanks to all these techniques, many aspects, such as the behaviour of the active material or the solid electrolyte interphase (SEI) and the lithiation mechanisms, are studied upon cycling. A clear picture of the failure mechanisms of nano-Si based electrodes is provided. In particular, by combining Hg analyses, SEM observations of electrode cross-sections, and EIS measurements, we follow the evolution of the porosity within the electrode. For the first time, our results clearly show a real dynamic of the pore size distribution: the first cycles lead to the formation of a micrometric porosity which is not present initially. During the following cycles, these large pores are progressively filled up with SEI products which form continuously at the Si particle surface. Thus, from the 50th cycle, Li(+) ion diffusion is dramatically hindered leading to a strongly heterogeneous lithiation of the electrode and a rapid capacity fading.

  15. Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium.

    PubMed

    Vásquez, Vanessa; Ozcan, Mutlu; Nishioka, Renato; Souza, Rodrigo; Mesquita, Alfredo; Pavanelli, Carlos

    2008-01-01

    This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N= 84) were cast in cpTi, followed by 150- microm aluminum oxide airborne particle abrasion at a designated area of the frameworks (8 x 3 mm). Bonder and opaque ceramic were applied on the frameworks, and then the corresponding ceramic (Triceram, Super Porcelain Ti-22, Vita Titankeramik) was fired onto them (thickness: 1 mm). Half of the specimens from each ceramic-metal combination were randomly tested without aging (only water storage at 37 degrees C for 24 hours), while the other half were mechanically loaded (20,000 cycles under 10 N load, immersion in distilled water at 37 degrees C) and thermocycled (3,000 cycles, between 5-55 degrees C, dwell time of 13 seconds). After the flexural strength test, failure types were noted. Mechanical and thermal cycling decreased the mean flexural strength values significantly (p<0.05) for all the three ceramic-cpTi combinations tested when compared to the control group. In all the three groups, failure type was exclusively adhesive at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface except for a visible oxide layer.

  16. Mechanism of Silicon Electrode Aging upon Cycling in Full Lithium-Ion Batteries.

    PubMed

    Delpuech, Nathalie; Dupre, Nicolas; Moreau, Philippe; Bridel, Jean-Sebastian; Gaubicher, Joel; Lestriez, Bernard; Guyomard, Dominique

    2016-04-21

    Understanding the aging mechanism of silicon-based negative electrodes for lithium-ion batteries upon cycling is essential to solve the problem of low coulombic efficiency and capacity fading and further to implement this new high-capacity material in commercial cells. Nevertheless, such studies have so far focused on half cells in which silicon is cycled versus an infinite reservoir of lithium. In the present work, the aging mechanism of silicon-based electrodes is studied upon cycling in a full Li-ion cell configuration with LiCoO2 as the positive electrode. Postmortem analyses of both electrodes clearly indicate that neither one of them contains lithium and that no discernible degradation results from the cycling. The aging mechanism can be explained by the reduction of solvent molecules. Electrons extracted from the positive electrode are responsible for an internal imbalance in the cell, which results in progressive slippage of the electrodes and reduces the compositional range of cyclable lithium ions for both electrodes. PMID:26915951

  17. RecO protein initiates DNA recombination and strand annealing through two alternative DNA binding mechanisms.

    PubMed

    Ryzhikov, Mikhail; Gupta, Richa; Glickman, Michael; Korolev, Sergey

    2014-10-17

    Recombination mediator proteins (RMPs) are important for genome stability in all organisms. Several RMPs support two alternative reactions: initiation of homologous recombination and DNA annealing. We examined mechanisms of RMPs in both reactions with Mycobacterium smegmatis RecO (MsRecO) and demonstrated that MsRecO interacts with ssDNA by two distinct mechanisms. Zinc stimulates MsRecO binding to ssDNA during annealing, whereas the recombination function is zinc-independent and is regulated by interaction with MsRecR. Thus, different structural motifs or conformations of MsRecO are responsible for interaction with ssDNA during annealing and recombination. Neither annealing nor recombinase loading depends on MsRecO interaction with the conserved C-terminal tail of single-stranded (ss) DNA-binding protein (SSB), which is known to bind Escherichia coli RecO. However, similarly to E. coli proteins, MsRecO and MsRecOR do not dismiss SSB from ssDNA, suggesting that RMPs form a complex with SSB-ssDNA even in the absence of binding to the major protein interaction motif. We propose that alternative conformations of such complexes define the mechanism by which RMPs initiate the repair of stalled replication and support two different functions during recombinational repair of DNA breaks. PMID:25170075

  18. Global transcription analysis of Krebs tricarboxylic acid cycle mutants reveals an alternating pattern of gene expression and effects on hypoxic and oxidative genes.

    PubMed

    McCammon, Mark T; Epstein, Charles B; Przybyla-Zawislak, Beata; McAlister-Henn, Lee; Butow, Ronald A

    2003-03-01

    To understand the many roles of the Krebs tricarboxylic acid (TCA) cycle in cell function, we used DNA microarrays to examine gene expression in response to TCA cycle dysfunction. mRNA was analyzed from yeast strains harboring defects in each of 15 genes that encode subunits of the eight TCA cycle enzymes. The expression of >400 genes changed at least threefold in response to TCA cycle dysfunction. Many genes displayed a common response to TCA cycle dysfunction indicative of a shift away from oxidative metabolism. Another set of genes displayed a pairwise, alternating pattern of expression in response to contiguous TCA cycle enzyme defects: expression was elevated in aconitase and isocitrate dehydrogenase mutants, diminished in alpha-ketoglutarate dehydrogenase and succinyl-CoA ligase mutants, elevated again in succinate dehydrogenase and fumarase mutants, and diminished again in malate dehydrogenase and citrate synthase mutants. This pattern correlated with previously defined TCA cycle growth-enhancing mutations and suggested a novel metabolic signaling pathway monitoring TCA cycle function. Expression of hypoxic/anaerobic genes was elevated in alpha-ketoglutarate dehydrogenase mutants, whereas expression of oxidative genes was diminished, consistent with a heme signaling defect caused by inadequate levels of the heme precursor, succinyl-CoA. These studies have revealed extensive responses to changes in TCA cycle function and have uncovered new and unexpected metabolic networks that are wired into the TCA cycle.

  19. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling

    PubMed Central

    CASSELLI, Denise Sá Maia; FARIA-E-SILVA, André Luis; CASSELLI, Henrique; MARTINS, Luis Roberto Marcondes

    2013-01-01

    Objective: This study evaluated the effect of the margin location and an adhesive system on the marginal adaptation of composite restorations. Material and Methods: Class V cavities were prepared in bovine teeth with the gingival margin on the dentin and the incisal margin on the enamel. The cavities were restored with a micro-hybrid composite resin using an etch-and-rinse [Single Bond 2 (SB)] or a self-etching adhesive [Clearfil SE Bond (CL)]. After finishing and polishing the restorations, epoxy replicas were prepared. The marginal adaptation was analyzed using scanning electronic microscopy (SEM, 500 x magnification). The higher gap width in each margin was recorded (T0). After the first evaluation, the samples were submitted to thermal cycling (2,000 cycles of 5ºC±2ºC followed by 55ºC±2ºC - T1) and mechanical cycling (100,000 cycles of 50 kN and 2 Hz - T2). Replicas of samples were rebuilt after each cycling and analyzed under SEM. The data were submitted to Mann-Whitney, Wilcoxon and Friedman testing (a=0.05). Results: The SB presented higher gaps in the dentin than the enamel, while there was no difference between the substrate for the CL. In the dentin, the CL showed better marginal sealing than the SB. The opposite occurred in the enamel. There were no significant differences between the baseline, thermal and mechanical cycling for any experimental condition. Conclusions: The outcomes of the present study showed that the adhesive system and margin location have an important effect on the marginal adaptation of composite restorations. PMID:23559115

  20. Coordination of DNA damage tolerance mechanisms with cell cycle progression in fission yeast

    PubMed Central

    Callegari, A. John; Kelly, Thomas J.

    2016-01-01

    ABSTRACT DNA damage tolerance (DDT) mechanisms allow cells to synthesize a new DNA strand when the template is damaged. Many mutations resulting from DNA damage in eukaryotes are generated during DDT when cells use the mutagenic translesion polymerases, Rev1 and Polζ, rather than mechanisms with higher fidelity. The coordination among DDT mechanisms is not well understood. We used live-cell imaging to study the function of DDT mechanisms throughout the cell cycle of the fission yeast Schizosaccharomyces pombe. We report that checkpoint-dependent mitotic delay provides a cellular mechanism to ensure the completion of high fidelity DDT, largely by homology-directed repair (HDR). DDT by mutagenic polymerases is suppressed during the checkpoint delay by a mechanism dependent on Rad51 recombinase. When cells pass the G2/M checkpoint and can no longer delay mitosis, they completely lose the capacity for HDR and simultaneously exhibit a requirement for Rev1 and Polζ. Thus, DDT is coordinated with the checkpoint response so that the activity of mutagenic polymerases is confined to a vulnerable period of the cell cycle when checkpoint delay and HDR are not possible. PMID:26652183

  1. Coordination of DNA damage tolerance mechanisms with cell cycle progression in fission yeast.

    PubMed

    Callegari, A John; Kelly, Thomas J

    2016-01-01

    DNA damage tolerance (DDT) mechanisms allow cells to synthesize a new DNA strand when the template is damaged. Many mutations resulting from DNA damage in eukaryotes are generated during DDT when cells use the mutagenic translesion polymerases, Rev1 and Polζ, rather than mechanisms with higher fidelity. The coordination among DDT mechanisms is not well understood. We used live-cell imaging to study the function of DDT mechanisms throughout the cell cycle of the fission yeast Schizosaccharomyces pombe. We report that checkpoint-dependent mitotic delay provides a cellular mechanism to ensure the completion of high fidelity DDT, largely by homology-directed repair (HDR). DDT by mutagenic polymerases is suppressed during the checkpoint delay by a mechanism dependent on Rad51 recombinase. When cells pass the G2/M checkpoint and can no longer delay mitosis, they completely lose the capacity for HDR and simultaneously exhibit a requirement for Rev1 and Polζ. Thus, DDT is coordinated with the checkpoint response so that the activity of mutagenic polymerases is confined to a vulnerable period of the cell cycle when checkpoint delay and HDR are not possible. PMID:26652183

  2. Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States

    SciTech Connect

    Tessum, Christopher W.; Hill, Jason D.; Marshall, Julian D.

    2014-12-30

    Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration–response, and economic health impact modeling for ozone (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or “grid average” electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles.

  3. Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States

    PubMed Central

    Hill, Jason D.; Marshall, Julian D.

    2014-01-01

    Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration–response, and economic health impact modeling for ozone (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or “grid average” electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles. PMID:25512510

  4. Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States.

    PubMed

    Tessum, Christopher W; Hill, Jason D; Marshall, Julian D

    2014-12-30

    Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration-response, and economic health impact modeling for ozone (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or "grid average" electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles. PMID:25512510

  5. Total fuel-cycle analysis of heavy-duty vehicles using biofuels and natural gas-based alternative fuels.

    PubMed

    Meyer, Patrick E; Green, Erin H; Corbett, James J; Mas, Carl; Winebrake, James J

    2011-03-01

    Heavy-duty vehicles (HDVs) present a growing energy and environmental concern worldwide. These vehicles rely almost entirely on diesel fuel for propulsion and create problems associated with local pollution, climate change, and energy security. Given these problems and the expected global expansion of HDVs in transportation sectors, industry and governments are pursuing biofuels and natural gas as potential alternative fuels for HDVs. Using recent lifecycle datasets, this paper evaluates the energy and emissions impacts of these fuels in the HDV sector by conducting a total fuel-cycle (TFC) analysis for Class 8 HDVs for six fuel pathways: (1) petroleum to ultra low sulfur diesel; (2) petroleum and soyoil to biodiesel (methyl soy ester); (3) petroleum, ethanol, and oxygenate to e-diesel; (4) petroleum and natural gas to Fischer-Tropsch diesel; (5) natural gas to compressed natural gas; and (6) natural gas to liquefied natural gas. TFC emissions are evaluated for three greenhouse gases (GHGs) (carbon dioxide, nitrous oxide, and methane) and five other pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter, and sulfur oxides), along with estimates of total energy and petroleum consumption associated with each of the six fuel pathways. Results show definite advantages with biodiesel and compressed natural gas for most pollutants, negligible benefits for e-diesel, and increased GHG emissions for liquefied natural gas and Fischer-Tropsch diesel (from natural gas). PMID:21416755

  6. Total fuel-cycle analysis of heavy-duty vehicles using biofuels and natural gas-based alternative fuels.

    PubMed

    Meyer, Patrick E; Green, Erin H; Corbett, James J; Mas, Carl; Winebrake, James J

    2011-03-01

    Heavy-duty vehicles (HDVs) present a growing energy and environmental concern worldwide. These vehicles rely almost entirely on diesel fuel for propulsion and create problems associated with local pollution, climate change, and energy security. Given these problems and the expected global expansion of HDVs in transportation sectors, industry and governments are pursuing biofuels and natural gas as potential alternative fuels for HDVs. Using recent lifecycle datasets, this paper evaluates the energy and emissions impacts of these fuels in the HDV sector by conducting a total fuel-cycle (TFC) analysis for Class 8 HDVs for six fuel pathways: (1) petroleum to ultra low sulfur diesel; (2) petroleum and soyoil to biodiesel (methyl soy ester); (3) petroleum, ethanol, and oxygenate to e-diesel; (4) petroleum and natural gas to Fischer-Tropsch diesel; (5) natural gas to compressed natural gas; and (6) natural gas to liquefied natural gas. TFC emissions are evaluated for three greenhouse gases (GHGs) (carbon dioxide, nitrous oxide, and methane) and five other pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter, and sulfur oxides), along with estimates of total energy and petroleum consumption associated with each of the six fuel pathways. Results show definite advantages with biodiesel and compressed natural gas for most pollutants, negligible benefits for e-diesel, and increased GHG emissions for liquefied natural gas and Fischer-Tropsch diesel (from natural gas).

  7. Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States.

    PubMed

    Tessum, Christopher W; Hill, Jason D; Marshall, Julian D

    2014-12-30

    Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration-response, and economic health impact modeling for ozone (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or "grid average" electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles.

  8. Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States

    DOE PAGESBeta

    Tessum, Christopher W.; Hill, Jason D.; Marshall, Julian D.

    2014-12-30

    Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration–response, and economic health impact modeling for ozonemore » (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or “grid average” electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles.« less

  9. Evaluating environmental impacts of alternative construction waste management approaches using supply-chain-linked life-cycle analysis.

    PubMed

    Kucukvar, Murat; Egilmez, Gokhan; Tatari, Omer

    2014-06-01

    Waste management in construction is critical for the sustainable treatment of building-related construction and demolition (C&D) waste materials, and recycling of these wastes has been considered as one of the best strategies in minimization of C&D debris. However, recycling of C&D materials may not always be a feasible strategy for every waste type and therefore recycling and other waste treatment strategies should be supported by robust decision-making models. With the aim of assessing the net carbon, energy, and water footprints of C&D recycling and other waste management alternatives, a comprehensive economic input-output-based hybrid life-cycle assessment model is developed by tracing all of the economy-wide supply-chain impacts of three waste management strategies: recycling, landfilling, and incineration. Analysis results showed that only the recycling of construction materials provided positive environmental footprint savings in terms of carbon, energy, and water footprints. Incineration is a better option as a secondary strategy after recycling for water and energy footprint categories, whereas landfilling is found to be as slightly better strategy when carbon footprint is considered as the main focus of comparison. In terms of construction materials' environmental footprint, nonferrous metals are found to have a significant environmental footprint reduction potential if recycled.

  10. Evaluating environmental impacts of alternative construction waste management approaches using supply-chain-linked life-cycle analysis.

    PubMed

    Kucukvar, Murat; Egilmez, Gokhan; Tatari, Omer

    2014-06-01

    Waste management in construction is critical for the sustainable treatment of building-related construction and demolition (C&D) waste materials, and recycling of these wastes has been considered as one of the best strategies in minimization of C&D debris. However, recycling of C&D materials may not always be a feasible strategy for every waste type and therefore recycling and other waste treatment strategies should be supported by robust decision-making models. With the aim of assessing the net carbon, energy, and water footprints of C&D recycling and other waste management alternatives, a comprehensive economic input-output-based hybrid life-cycle assessment model is developed by tracing all of the economy-wide supply-chain impacts of three waste management strategies: recycling, landfilling, and incineration. Analysis results showed that only the recycling of construction materials provided positive environmental footprint savings in terms of carbon, energy, and water footprints. Incineration is a better option as a secondary strategy after recycling for water and energy footprint categories, whereas landfilling is found to be as slightly better strategy when carbon footprint is considered as the main focus of comparison. In terms of construction materials' environmental footprint, nonferrous metals are found to have a significant environmental footprint reduction potential if recycled. PMID:24855225

  11. Top-color jungle gym: An alternative to the seesaw mechanism

    NASA Astrophysics Data System (ADS)

    Georgi, Howard; Grant, Aaron K.

    2001-01-01

    We discuss an alternative to the top-color seesaw mechanism. In our scheme, all the light quarks carry top-color, and there are many composite SU(2) doublets. This makes it possible to get the observed t quark mass and observed SU(2)×U(1) breaking in a way that is quite different from the classic seesaw mechanism. We discuss a model of this kind that arises naturally in the context of dynamically broken top-color. There are many composite scalars in a theory of this kind. This has important effects on the Pagels-Stokar relation and the Higgs boson mass. We find mHiggs<~330 GeV, lighter than in typical top-color models. We also show that the electroweak singlet quarks in such a model can be lighter than the corresponding quarks in a seesaw model.

  12. Induced thermo-mechanical stress in CPV receivers with cycled high intensity light

    NASA Astrophysics Data System (ADS)

    Pérez, Valentín; Antón, Ignacio; Herrero, Rebeca; Nogueira, Eduardo; Núñez, Rubén; del Cañizo, Carlos; Sala, Gabriel

    2014-09-01

    CPV receivers are made of materials with very different lineal expansion coefficients. Strong variations in DNI due to the passage of clouds can cause sudden temperature changes that creates mechanical stress. For common solder and metal filled polymers the plastic limit could be reached causing substantial fatigue. The best forecast of receiver reliability is therefore achieved by applying an intermittent light source with nominal irradiance level and a number of cycles equal to the expected cloud passages for a given site. The UPM has developed specialized equipment, dubbed the LYSS (Light cYcling Stressing Source), for carrying out such experiments. The small thermal capacity of receivers allows simulating more than 25000 cycles per week. The number of deep transients expected for Madrid in 30 years operation, based on available data, is about 45000. We are currently using the system to cycle a "Ge/Ag Epoxy/aluminum" receiver, which shows no degradation after 20000 cycles. The equipment can cast up to 200 and 70 W/cm2 on 0.1 and 1 cm2 cells, respectively.

  13. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  14. Separation Mechanism of Primary Silicon from Hypereutectic Al-Si Melts Under Alternating Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Xue, Haiyang; Lv, Guoqiang; Ma, Wenhui; Chen, Daotong; Yu, Jie

    2015-07-01

    Solar grade silicon (SOG-Si) and hypereutectic Al-Si alloys with low silicon (silicon composition below 25 pct) can be successfully obtained by separation of hypereutectic Al-Si alloy with high silicon (silicon composition above 30 pct) under an alternating electromagnetic field after post-processing. To explore the separation mechanism in detail, experiments were conducted in this study using a high-frequency induction furnace with different pulling conditions of the crucible which is loaded with Al-45 wt pct Si melt. Results demonstrate that the separation of hypereutectic Al-Si alloy is feasible through either a pull-up or drop-down process. The height of each separation interface between the compact and sparse parts of the primary silicon decrease as the pull-up distance rose. When the pulling rate is very low, resultant morphologies of compact primary silicon are rounded and polygonal, allowing for more effective separation of the primary silicon. A novel physical model is presented here based on the experimental results and simulation. The model can be used to effectively describe the separation mechanism of primary silicon from hypereutectic Al-Si melts under alternating electromagnetic fields.

  15. Attentional Biases toward Attractive Alternatives and Rivals: Mechanisms Involved in Relationship Maintenance among Chinese Women.

    PubMed

    Ma, Yidan; Zhao, Guang; Tu, Shen; Zheng, Yong

    2015-01-01

    A long-term romantic relationship can offer many benefits to committed individuals. Thus, humans possess relationship maintenance mechanisms to protect against threats from those who serve as attractive alternatives or intrasexual rivals. Many studies have indicated that romantic love can act as a commitment device to activate these mechanisms. To examine the attentional bias associated with relationship maintenance among 108 college students (49 single and 59 committed females) in China, we used a semantic priming procedure to activate mental representations associated with romantic love and then asked participants to complete a dot-probe task for the purpose of making a distinction between the engage and disengage components of attention. No significant engaging effects toward attractive faces were observed among committed females, but the following significant disengaging effects were found: when primed with romantic love, single females showed increased attention toward and difficulty in disengaging from attractive male faces, whereas females already in a committed relationship did not alter their attention, remaining as inattentive to attractive alternatives as they were in the baseline condition. In addition, committed females responded to love priming by exhibiting difficulty in disengaging from attractive rivals. The present findings provide evidence in the Chinese cultural context for the existence of early-stage attentional processes in the domain of relationship maintenance that committed Chinese females protected an ongoing relationship by not only being inattentive to attractive males who could serve as attractive alternatives, but also being more attentive to attractive females who could be potential rivals when mental representations associated with romantic love were primed.

  16. Attentional Biases toward Attractive Alternatives and Rivals: Mechanisms Involved in Relationship Maintenance among Chinese Women

    PubMed Central

    Ma, Yidan; Zhao, Guang; Tu, Shen; Zheng, Yong

    2015-01-01

    A long-term romantic relationship can offer many benefits to committed individuals. Thus, humans possess relationship maintenance mechanisms to protect against threats from those who serve as attractive alternatives or intrasexual rivals. Many studies have indicated that romantic love can act as a commitment device to activate these mechanisms. To examine the attentional bias associated with relationship maintenance among 108 college students (49 single and 59 committed females) in China, we used a semantic priming procedure to activate mental representations associated with romantic love and then asked participants to complete a dot-probe task for the purpose of making a distinction between the engage and disengage components of attention. No significant engaging effects toward attractive faces were observed among committed females, but the following significant disengaging effects were found: when primed with romantic love, single females showed increased attention toward and difficulty in disengaging from attractive male faces, whereas females already in a committed relationship did not alter their attention, remaining as inattentive to attractive alternatives as they were in the baseline condition. In addition, committed females responded to love priming by exhibiting difficulty in disengaging from attractive rivals. The present findings provide evidence in the Chinese cultural context for the existence of early-stage attentional processes in the domain of relationship maintenance that committed Chinese females protected an ongoing relationship by not only being inattentive to attractive males who could serve as attractive alternatives, but also being more attentive to attractive females who could be potential rivals when mental representations associated with romantic love were primed. PMID:26309232

  17. Mechanisms of dissolved organic carbon cycling in an ocean margin. Final technical report

    SciTech Connect

    Benner, R.

    1997-11-24

    Dissolved organic carbon (DOC) is the largest reservoir of organic carbon in the ocean, and the objectives of this project were to investigate the mechanisms and pathways of DOC formation and consumption in seawater. Carbohydrates are the most abundant form of DOC, and this project included measurements of dissolved carbohydrates as well as DOC to help delineate the cycling of DOC. Many of the methods and approaches for investigating DOC production were developed as part of this project.

  18. Modeling mechanical degradation in lithium ion batteries during cycling: Solid electrolyte interphase fracture

    NASA Astrophysics Data System (ADS)

    Laresgoiti, Izaro; Käbitz, Stefan; Ecker, Madeleine; Sauer, Dirk Uwe

    2015-12-01

    During cycling, mechanical stresses can occur in the composite electrode, inside the active material, but also in the solid electrolyte interphase layer. A mechanical model is proposed based on a system made of a spherical graphite particle surrounded by the solid electrolyte interphase layer. During lithium intercalation or de-intercalation, stresses in the graphite are produced, governed by the diffusion induced stress phenomena and in the solid electrolyte interphase, driven by the graphite expansion. The stresses in both materials were simulated and a sensitivity analysis was performed to clarify the influence of principal parameters on both processes. Finally, assuming that the solid electrolyte interphase is the weakest material and therefore more prone to fracture than graphite, the experimental capacity fade during cycling was modeled based on its break and repair effect rather than on the fracture of the active material. The mechanical model of the solid electrolyte interphase was implemented in a single particle lithium ion battery model in order to reproduce capacity fade during battery lifetime. The model results were compared against cycle life aging experimental data, reproducing accurately the influence of the depth of discharge as well as the average state of charge on the capacity fade.

  19. Similarity between quantum mechanics and thermodynamics: entropy, temperature, and Carnot cycle.

    PubMed

    Abe, Sumiyoshi; Okuyama, Shinji

    2011-02-01

    The similarity between quantum mechanics and thermodynamics is discussed. It is found that if the Clausius equality is imposed on the Shannon entropy and the analog of the quantity of heat, then the value of the Shannon entropy comes to formally coincide with that of the von Neumann entropy of the canonical density matrix, and pure-state quantum mechanics apparently transmutes into quantum thermodynamics. The corresponding quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is studied, and its efficiency is shown to be identical to the classical one.

  20. An integrative process model of leadership: examining loci, mechanisms, and event cycles.

    PubMed

    Eberly, Marion B; Johnson, Michael D; Hernandez, Morela; Avolio, Bruce J

    2013-09-01

    Utilizing the locus (source) and mechanism (transmission) of leadership framework (Hernandez, Eberly, Avolio, & Johnson, 2011), we propose and examine the application of an integrative process model of leadership to help determine the psychological interactive processes that constitute leadership. In particular, we identify the various dynamics involved in generating leadership processes by modeling how the loci and mechanisms interact through a series of leadership event cycles. We discuss the major implications of this model for advancing an integrative understanding of what constitutes leadership and its current and future impact on the field of psychological theory, research, and practice.

  1. Mechanisms for alternative treatments in Parkinson's disease: acupuncture, tai chi, and other treatments.

    PubMed

    Ghaffari, Bijan D; Kluger, Benzi

    2014-06-01

    At least 40% of patients with Parkinson's disease (PD) use one or more forms of alternative therapy (AT) to complement standard treatments. This article reviews the commonest forms of AT for PD, including acupuncture, tai chi, yoga, mindfulness, massage, herbal medicine, and cannabis. We discuss the current evidence for the clinical efficacy of each AT and discuss potential mechanisms, including those suggested by animal and human studies. With a few notable exceptions, none of the treatments examined were investigated rigorously enough to draw definitive conclusions about efficacy or mechanism. Tai chi, acupuncture, Mucuna pruriens, cannabinoids, and music therapy have all been proposed to work through specific mechanisms, although current evidence is insufficient to support or refute these claims, with the possible exception of Mucuna pruriens (which contains levodopa). It is likely that most ATs predominantly treat PD patients through general mechanisms, including placebo effects, stress reduction, and improved mood and sleep, and AT may provide patients with a greater locus of control regarding their illness. PMID:24760476

  2. Application of food waste disposers and alternate cycles process in small-decentralized towns: a case study.

    PubMed

    Battistoni, Paolo; Fatone, Francesco; Passacantando, Daniele; Bolzonella, David

    2007-02-01

    The use of food waste disposers (FWDs) can be an interesting option to integrate the management of municipal wastewaters and household organic waste in small towns and decentralized areas. This strategy can be even more environmentally friendly if a suitable treatment process of the resulting sewage is performed in order to control nutrients emission. However, still nowadays, part of the scientific and technical community considers the application of this technology a possible source of problems. In this study, the FWDs were applied, with a market penetration factor of 67%, in a mountain village of 250 inhabitants. Further, the existing wastewater treatment plant (WWTP) was upgraded by applying an automatically controlled alternate cycles process for the management of nutrients removal. With specific reference to the observed results, the impact of the ground food waste on the sewerage system did not show particular solids sedimentation or significant hydraulic overflows. Further, the WWTP was able to face the overloads of 11, 55 and 2g per capita per day of TSS, COD and TN, respectively. Then, the increase of the readily biodegradable COD (rbCOD/COD from 0.20 to 0.25) and the favourable COD/TN ratio (from 9.9 to 12) led to a specific denitrification rate of some 0.06kgNO(3)-N/(kg MLVSS day). Therefore, not only COD removal, but also the total nitrogen removal increased: the denitrification efficiency reached 85%. That led to a better exploitation of the nitrogen-bound oxygen and a consequent reduction of energy requirements of 39%. The final economic evaluation showed the benefits of the application of this technology with a pay back time of 4-5 years.

  3. The life cycle of rice: LCA of alternative agri-food chain management systems in Vercelli (Italy).

    PubMed

    Blengini, Gian Andrea; Busto, Mirko

    2009-03-01

    The Vercelli rice district in northern Italy plays a key role in the agri-food industry in a country which accounts for more than 50% of the EU rice production and exports roughly 70%. However, although wealth and jobs are created, the sector is said to be responsible for environmental impacts that are increasingly being perceived as topical. As a complex and comprehensive environmental evaluation is necessary to understand and manage the environmental impact of the agri-food chain, the Life Cycle Assessment (LCA) methodology has been applied to the rice production system: from the paddy field to the supermarket. The LCA has pointed out the magnitude of impact per kg of delivered white milled rice: a CO2eq emission of 2.9 kg, a primary energy consumption of 17.8 MJ and the use of 4.9 m3 of water for irrigation purposes. Improvement scenarios have been analysed considering alternative rice farming and food processing methods, such as organic and upland farming, as well as parboiling. The research has shown that organic and upland farming have the potential to decrease the impact per unit of cultivated area. However, due to the lower grain yields, the environmental benefits per kg of the final products are greatly reduced in the case of upland rice production and almost cancelled for organic rice. LCA has proved to be an effective tool for understanding the eco-profile of Italian rice and should be used for transparent and credible communication between suppliers and their customers.

  4. Sun-dried raisins are a cost-effective alternative to Sports Jelly Beans in prolonged cycling.

    PubMed

    Rietschier, Helena L; Henagan, Tara M; Earnest, Conrad P; Baker, Birgitta L; Cortez, Cory C; Stewart, Laura K

    2011-11-01

    The purpose of this study was to examine the effects of a natural carbohydrate (CHO) source in the form of sun-dried raisins (SDRs) vs. Sports Jelly Beans™ (SJBs) on endurance performance in trained cyclists and triathletes. Ten healthy men (18-33 years) completed 1 water-only acclimatization exercise trial and 2 randomized exercise trials administered in a crossover fashion. Each trial consisted of a 120-minute constant-intensity glycogen depletion period followed by a 10-km time trial (TT). During each experimental trial, participants consumed isocaloric amounts of SDRs or SJBs in 20-minute intervals. Measurements included time to complete 10-km TT, power output during 10-km TT, blood glucose levels and respiratory exchange ratio during glycogen depletion period, rate of perceived exertion (RPE), 'flow' questionnaire responses, and a hedonic (i.e., pleasantness) sensory acceptance test. There were no significant differences in endurance performance for TT time (SDRs vs. SJBs, 17.3 ± 0.4 vs. 17.3 ± 0.4 seconds) or power (229.3 ± 13.0 vs. 232.0 ± 13.6 W), resting blood glucose levels (5.8 ± 04 mmol·L(-1) for SDRs and 5.4 ± 0.2 mmol·L(-1) for SJBs), RPE, or flow experiences between SDR and SJB trials. However, the mean sensory acceptance scores were significantly higher for the SDRs compared to the SJBs (50.7 ± 1.7 vs. 44.3 ± 2.7). Consuming SDRs or SJBs during 120 minutes of intense cycling results in similar subsequent TT performances and are equally effective in maintaining blood glucose levels during exercise. Therefore, SDRs are a natural, pleasant, cost-effective CHO alternative to commercial SJBs that can be used during moderate- to high-intensity endurance exercise.

  5. Mechanical and low-cycle fatigue behavior of stainless reinforcing steel for earthquake engineering applications

    NASA Astrophysics Data System (ADS)

    Zhou, Yihui; Ou, Yu-Chen; Lee, George C.; O'Connor, Jerome S.

    2010-09-01

    Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.

  6. Long-term changes of the diurnal temperature cycle: implications about mechanisms of global climate change

    NASA Astrophysics Data System (ADS)

    Hansen, J.; Sato, M.; Ruedy, R.

    We use a global climate model to investigate the impact of a wide range of radiative forcing and feedback mechanisms on the diurnal cycle of surface air temperature. This allows us not only to rule out many potential explanations for observed diurnal changes, but to infer fundamental information concerning the nature and location of the principal global climate forcings of this century. We conclude that the observed changes of the diurnal cycle result neither from natural climate variability nor a globally-distributed forcing, but rather they require the combination of a (negative) radiative forcing located primarily over continental regions together with the known globally-distributed forcing due to anthropogenic greenhouse gases. Tropospheric aerosols can account for part of the continentally-located forcing, but alone they do not damp the diurnal cycle as observed. Only an increase of continental cloud cover, possibly a consequence of anthropogenic aerosols, can damp the diurnal cycle by an amount comparable to observations. A corollary of these results is quantitative confirmation of the widely held suspicion that anthropogenic greenhouse gas warming has been substantially counterbalanced by a forced cooling. Under the assumption that the cloud change is sulfate driven, a further implication is that the net rate of global warming is likely to increase substantially in coming years. We note that, on the long run, the daily maximum temperature will increase by an amount not much less than the increase of the mean temperature.

  7. Fatigue Response of a PZT Multilayer Actuator under High-Field Electric Cycling with Mechanical Preload

    SciTech Connect

    Wang, Hong; Wereszczak, Andrew A; Lin, Hua-Tay

    2009-01-01

    An electric fatigue test system has been developed for piezoelectric actuator with a mechanical loading capability. Fatigue responses of a lead zirconate titanate (PZT) multilayer actuator (MLA) with a plate-through electrode configuration have been studied under an electric field (1.7 times that of a coercive field of PZT material) and a concurrent mechanical preload (30.0 MPa). A total of 1.0x10^9 cycles were carried out. Variations in charge density and mechanical strain under a high electric field and constant mechanical loads were observed during the fatigue test. The dc and the first harmonic (at 10 Hz) dielectric and piezoelectric coefficients were subsequently characterized by using FFT (Fast Fourier Transformation). It has been observed that both the dielectric and the piezoelectric coefficients underwent a monotonic decrease prior to 2.86x10^8 cycles under the relevant preload, and then fluctuated to a certain extent. Both the dielectric loss tangent and the piezoelectric loss tangent also exhibited the fluctuations after a certain amount of drop but at different levels relative to the pre-fatigue. And finally, the results were discussed with respect to domain wall mobility, microcracking, and other pre-existing anomalies.

  8. Effect of Temperature Cycling on Conduction Mechanisms in CdTe Thin Films

    NASA Astrophysics Data System (ADS)

    Srivastav, V.; Pal, R.; Saini, N.; Saxena, R. S.; Bhan, R. K.; Sareen, L.; Singh, K. P.; Sharma, R. K.; Venkataraman, V.

    2013-03-01

    CdTe thin films of 500 Å thickness prepared by thermal evaporation technique were analyzed for leakage current and conduction mechanisms. Metal-insulator-metal (MIM) capacitors were fabricated using these films as a dielectric. These films have many possible applications, such as passivation for infrared diodes that operate at low temperatures (80 K). Direct-current (DC) current-voltage ( I- V) and capacitance-voltage ( C- V) measurements were performed on these films. Furthermore, the films were subjected to thermal cycling from 300 K to 80 K and back to 300 K. Typical minimum leakage currents near zero bias at room temperature varied between 0.9 nA and 0.1 μA, while low-temperature leakage currents were in the range of 9.5 pA to 0.5 nA, corresponding to resistivity values on the order of 108 Ω-cm and 1010 Ω-cm, respectively. Well-known conduction mechanisms from the literature were utilized for fitting of measured I- V data. Our analysis indicates that the conduction mechanism in general is Ohmic for low fields <5 × 104 V cm-1, while the conduction mechanism for fields >6 × 104 V cm-1 is modified Poole-Frenkel (MPF) and Fowler-Nordheim (FN) tunneling at room temperature. At 80 K, Schottky-type conduction dominates. A significant observation is that the film did not show any appreciable degradation in leakage current characteristics due to the thermal cycling.

  9. Effect of fast freeze-thaw cycles on mechanical properties of ordinary-air-entrained concrete.

    PubMed

    Shang, Huai-shuai; Cao, Wei-qun; Wang, Bin

    2014-01-01

    Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions.

  10. Mechanical Properties of Anisotropic Conductive Adhesive Film Under Hygrothermal Aging and Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Gao, Li-Lan; Chen, Xu; Gao, Hong

    2012-07-01

    Mechanical properties of anisotropic conductive adhesive film (ACF) were investigated experimentally under various environmental conditions. The temperature sweep test was conducted to investigate the effects of temperature on dynamical mechanical properties of the ACF. The ACF exhibited transitions to the glass state, viscoelastic state, and rubber state with increasing temperature, and its glass-transition temperature ( T g) was determined to be 149°C. The creep-recovery behaviors of the ACF were investigated, and it was found that the initial strains, instantaneous strains, and creep or recovery rates increased with increasing temperature. No obvious creep phenomenon was observed at low temperatures (≤0°C). The creep strain and creep rates at any time decreased with increasing hygrothermal aging time. The uniaxial tensile behaviors of the ACF were also investigated under hygrothermal aging and thermal cycling. The results show that the Young's modulus and tensile strength of the ACF decrease with increasing hygrothermal aging time; however, they increase at first and then decrease with increasing thermal cycling time. T g decreases slightly for the ACF after hygrothermal aging; however, it increases after thermal cycling.

  11. Effect of Fast Freeze-Thaw Cycles on Mechanical Properties of Ordinary-Air-Entrained Concrete

    PubMed Central

    Shang, Huai-shuai; Cao, Wei-qun; Wang, Bin

    2014-01-01

    Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions. PMID:24895671

  12. Alternative splicing modulates Kv channel clustering through a molecular ball and chain mechanism

    NASA Astrophysics Data System (ADS)

    Zandany, Nitzan; Marciano, Shir; Magidovich, Elhanan; Frimerman, Teddy; Yehezkel, Rinat; Shem-Ad, Tzilhav; Lewin, Limor; Abdu, Uri; Orr, Irit; Yifrach, Ofer

    2015-03-01

    Ion channel clustering at the post-synaptic density serves a fundamental role in action potential generation and transmission. Here, we show that interaction between the Shaker Kv channel and the PSD-95 scaffold protein underlying channel clustering is modulated by the length of the intrinsically disordered C terminal channel tail. We further show that this tail functions as an entropic clock that times PSD-95 binding. We thus propose a ‘ball and chain’ mechanism to explain Kv channel binding to scaffold proteins, analogous to the mechanism describing channel fast inactivation. The physiological relevance of this mechanism is demonstrated in that alternative splicing of the Shaker channel gene to produce variants of distinct tail lengths resulted in differential channel cell surface expression levels and clustering metrics that correlate with differences in affinity of the variants for PSD-95. We suggest that modulating channel clustering by specific spatial-temporal spliced variant targeting serves a fundamental role in nervous system development and tuning.

  13. Measuring the distribution of equity in terms of energy, environmental, and economic costs in the fuel cycles of alternative fuel vehicles with hydrogen pathway scenarios

    NASA Astrophysics Data System (ADS)

    Meyer, Patrick E.

    Numerous analyses exist which examine the energy, environmental, and economic tradeoffs between conventional gasoline vehicles and hydrogen fuel cell vehicles powered by hydrogen produced from a variety of sources. These analyses are commonly referred to as "E3" analyses because of their inclusion of Energy, Environmental, and Economic indicators. Recent research as sought a means to incorporate social Equity into E3 analyses, thus producing an "E4" analysis. However, E4 analyses in the realm of energy policy are uncommon, and in the realm of alternative transportation fuels, E4 analyses are extremely rare. This dissertation discusses the creation of a novel E4 simulation tool usable to weigh energy, environmental, economic, and equity trade-offs between conventional gasoline vehicles and alternative fuel vehicles, with specific application to hydrogen fuel cell vehicles. The model, dubbed the F uel Life-cycle Analysis of Solar Hydrogen -- Energy, Environment, Economic & Equity model, or FLASH-E4, is a total fuel-cycle model that combines energy, environmental, and economic analysis methodologies with the addition of an equity analysis component. The model is capable of providing results regarding total fuel-cycle energy consumption, emissions production, energy and environmental cost, and level of social equity within a population in which low-income drivers use CGV technology and high-income drivers use a number of advanced hydrogen FCV technologies. Using theories of equity and social indicators conceptually embodied in the Lorenz Curve and Gini Index, the equity of the distribution of societal energy and environmental costs are measured for a population in which some drivers use CGVs and other drivers use FCVs. It is found, based on baseline input data representative of the United States (US), that the distribution of energy and environmental costs in a population in which some drivers use CGVs and other drivers use natural gas-based hydrogen FCVs can be

  14. Means to an end: mechanisms of alternative polyadenylation of messenger RNA precursors

    PubMed Central

    Gruber, Andreas R; Martin, Georges; Keller, Walter; Zavolan, Mihaela

    2014-01-01

    Expression of mature messenger RNAs (mRNAs) requires appropriate transcription initiation and termination, as well as pre-mRNA processing by capping, splicing, cleavage, and polyadenylation. A core 3′-end processing complex carries out the cleavage and polyadenylation reactions, but many proteins have been implicated in the selection of polyadenylation sites among the multiple alternatives that eukaryotic genes typically have. In recent years, high-throughput approaches to map both the 3′-end processing sites as well as the binding sites of proteins that are involved in the selection of cleavage sites and in the processing reactions have been developed. Here, we review these approaches as well as the insights into the mechanisms of polyadenylation that emerged from genome-wide studies of polyadenylation across a range of cell types and states. WIREs RNA 2014, 5:183–196. doi: 10.1002/wrna.1206 PMID:24243805

  15. Candida Infections, Causes, Targets, and Resistance Mechanisms: Traditional and Alternative Antifungal Agents

    PubMed Central

    Spampinato, Claudia

    2013-01-01

    The genus Candida includes about 200 different species, but only a few species are human opportunistic pathogens and cause infections when the host becomes debilitated or immunocompromised. Candida infections can be superficial or invasive. Superficial infections often affect the skin or mucous membranes and can be treated successfully with topical antifungal drugs. However, invasive fungal infections are often life-threatening, probably due to inefficient diagnostic methods and inappropriate initial antifungal therapies. Here, we briefly review our current knowledge of pathogenic species of the genus Candida and yeast infection causes and then focus on current antifungal drugs and resistance mechanisms. An overview of new therapeutic alternatives for the treatment of Candida infections is also provided. PMID:23878798

  16. The Complementary and Alternative Medicine for Endometriosis: A Review of Utilization and Mechanism

    PubMed Central

    Kong, Sai; Zhang, Yue-Hui; Liu, Chen-Fang; Tsui, Ilene; Guo, Ying; Ai, Bei-Bei; Han, Feng-Juan

    2014-01-01

    Endometriosis (EM) is one of the common gynecological conditions causing menstrual and pelvic pain and affects 10%–15% of women of reproductive age. In recent years, the complementary and alternative medical (CAM) treatment for EM has become popular due to the few adverse reactions reported. The CAM therapy for EM includes several different treatments such as herbs (herbal prescription, extract, and patent), acupuncture, microwave physiotherapy, and Chinese herb medicine enema (CHM enema). These CAM therapies are effective at relieving dysmenorrhoea, shrinking adnexal masses, and promoting pregnancy, with less unpleasant side effects when compared to hormonal and surgical treatments. In this review, we focus on the status quo of CAM on EM and try to identify therapeutic efficacy and mechanisms based on some clinical and experimental studies. We hope to provide some instructive suggestions for clinical treatment and experimental research in the future. PMID:24701237

  17. The complementary and alternative medicine for endometriosis: a review of utilization and mechanism.

    PubMed

    Kong, Sai; Zhang, Yue-Hui; Liu, Chen-Fang; Tsui, Ilene; Guo, Ying; Ai, Bei-Bei; Han, Feng-Juan

    2014-01-01

    Endometriosis (EM) is one of the common gynecological conditions causing menstrual and pelvic pain and affects 10%-15% of women of reproductive age. In recent years, the complementary and alternative medical (CAM) treatment for EM has become popular due to the few adverse reactions reported. The CAM therapy for EM includes several different treatments such as herbs (herbal prescription, extract, and patent), acupuncture, microwave physiotherapy, and Chinese herb medicine enema (CHM enema). These CAM therapies are effective at relieving dysmenorrhoea, shrinking adnexal masses, and promoting pregnancy, with less unpleasant side effects when compared to hormonal and surgical treatments. In this review, we focus on the status quo of CAM on EM and try to identify therapeutic efficacy and mechanisms based on some clinical and experimental studies. We hope to provide some instructive suggestions for clinical treatment and experimental research in the future. PMID:24701237

  18. Static mechanical strain induces capillary endothelial cell cycle re-entry and sprouting

    NASA Astrophysics Data System (ADS)

    Zeiger, A. S.; Liu, F. D.; Durham, J. T.; Jagielska, A.; Mahmoodian, R.; Van Vliet, K. J.; Herman, I. M.

    2016-08-01

    Vascular endothelial cells are known to respond to a range of biochemical and time-varying mechanical cues that can promote blood vessel sprouting termed angiogenesis. It is less understood how these cells respond to sustained (i.e., static) mechanical cues such as the deformation generated by other contractile vascular cells, cues which can change with age and disease state. Here we demonstrate that static tensile strain of 10%, consistent with that exerted by contractile microvascular pericytes, can directly and rapidly induce cell cycle re-entry in growth-arrested microvascular endothelial cell monolayers. S-phase entry in response to this strain correlates with absence of nuclear p27, a cyclin-dependent kinase inhibitor. Furthermore, this modest strain promotes sprouting of endothelial cells, suggesting a novel mechanical ‘angiogenic switch’. These findings suggest that static tensile strain can directly stimulate pathological angiogenesis, implying that pericyte absence or death is not necessarily required of endothelial cell re-activation.

  19. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  20. The effects of thermal cycling on the physical and mechanical properties of [NZP] ceramics

    SciTech Connect

    Jackson, T.B.; Limaye, S.Y.; Porter, W.D.

    1994-12-31

    The [NZP] ceramics, sodium zirconium phosphate and its crystal structure analogs, are noted for their very low thermal expansion characteristics. What has not been widely studied is the effect of thermal cycling on physical and mechanical properties. Two [NZP] compositional series were selected (Ba{sub 1+x}Zr{sub 4}P{sub 6{minus}2x}Si{sub 2x}O{sub 24} and Ca{sub 1{minus}x}Sr{sub x}Zr{sub 4}P{sub 6}O{sub 24}) that exhibit varying bulk thermal expansion from positive to negative and varying degrees of thermal expansion anisotropy. The effect of thermal cycling, to 1,250 C, on the bulk thermal expansion and flexural strength of these ceramics is discussed in relationship to changes in density, thermal expansion anisotropy and microstructure.

  1. Rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms.

    PubMed

    Tian, Jihua; Wang, Yanhong; Liu, Xinyan; Zhou, Xiaoshuang; Li, Rongshan

    2015-07-01

    IgA nephropathy is the most frequent type of glomerulonephritis worldwide. The role of cell cycle regulation in the pathogenesis of IgA nephropathy has been studied. The present study was designed to explore whether rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms. After establishing an IgA nephropathy model, rats were randomly divided into four groups. Coomassie Brilliant Blue was used to measure the 24-h urinary protein levels. Renal function was determined using an autoanalyzer. Proliferation was assayed via Proliferating Cell Nuclear Antigen (PCNA) immunohistochemistry. Rat mesangial cells were cultured and divided into the six groups. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) and flow cytometry were used to detect cell proliferation and the cell cycle phase. Western blotting was performed to determine cyclin E, cyclin-dependent kinase 2, p27(Kip1), p70S6K/p-p70S6K, and extracellular signal-regulated kinase 1/2/p- extracellular signal-regulated kinase 1/2 protein expression. A low dose of the mammalian target of rapamycin (mTOR) inhibitor rapamycin prevented an additional increase in proteinuria, protected kidney function, and reduced IgA deposition in a model of IgA nephropathy. Rapamycin inhibited mesangial cell proliferation and arrested the cell cycle in the G1 phase. Rapamycin did not affect the expression of cyclin E and cyclin-dependent kinase 2. However, rapamycin upregulated p27(Kip1) at least in part via AKT (also known as protein kinase B)/mTOR. In conclusion, rapamycin can affect cell cycle regulation to inhibit mesangial cell proliferation, thereby reduce IgA deposition, and slow the progression of IgAN.

  2. Rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms

    PubMed Central

    Tian, Jihua; Wang, Yanhong; Liu, Xinyan; Zhou, Xiaoshuang

    2014-01-01

    IgA nephropathy is the most frequent type of glomerulonephritis worldwide. The role of cell cycle regulation in the pathogenesis of IgA nephropathy has been studied. The present study was designed to explore whether rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms. After establishing an IgA nephropathy model, rats were randomly divided into four groups. Coomassie Brilliant Blue was used to measure the 24-h urinary protein levels. Renal function was determined using an autoanalyzer. Proliferation was assayed via Proliferating Cell Nuclear Antigen (PCNA) immunohistochemistry. Rat mesangial cells were cultured and divided into the six groups. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) and flow cytometry were used to detect cell proliferation and the cell cycle phase. Western blotting was performed to determine cyclin E, cyclin-dependent kinase 2, p27Kip1, p70S6K/p-p70S6K, and extracellular signal-regulated kinase 1/2/p- extracellular signal-regulated kinase 1/2 protein expression. A low dose of the mammalian target of rapamycin (mTOR) inhibitor rapamycin prevented an additional increase in proteinuria, protected kidney function, and reduced IgA deposition in a model of IgA nephropathy. Rapamycin inhibited mesangial cell proliferation and arrested the cell cycle in the G1 phase. Rapamycin did not affect the expression of cyclin E and cyclin-dependent kinase 2. However, rapamycin upregulated p27Kip1 at least in part via AKT (also known as protein kinase B)/mTOR. In conclusion, rapamycin can affect cell cycle regulation to inhibit mesangial cell proliferation, thereby reduce IgA deposition, and slow the progression of IgAN. PMID:25349217

  3. Validity and reliability of an alternative method for measuring power output during six-second all-out cycling.

    PubMed

    Watson, Martin; Bibbo, Daniele; Duffy, Charles R; Riches, Philip E; Conforto, Silvia; Macaluso, Andrea

    2014-08-01

    In a laboratory setting where both a mechanically-braked cycling ergometer and a motion analysis (MA) system are available, flywheel angular displacement can be estimated by using MA. The purpose of this investigation was to assess the validity and reliability of a MA method for measuring maximal power output (Pmax) in comparison with a force transducer (FT) method. Eight males and eight females undertook three identical sessions, separated by 4 to 6 days; the first being a familiarization session. Individuals performed three 6-second sprints against 50% of the maximal resistance to complete two pedal revolutions with a 3-minute rest between trials. Power was determined independently using both MA and FT analyses. Validity: MA recorded significantly higher Pmax than FT (P < .05). Bland-Altman plots showed that there was a systematic bias in the difference between the measures of the two systems. This difference increased as power increased. Repeatability: Intraclass correlation coefficients were on average 0.90 ± 0.05 in males and 0.85 ± 0.08 in females. Measuring Pmax by MA, therefore, is as appropriate for use in exercise physiology research as Pmax measured by FT, provided that a bias between these measurements methods is allowed for. PMID:24977624

  4. Mechanical load on the ventilatory muscles during an incremental cycle ergometer test.

    PubMed

    Wanke, T; Formanek, D; Schenz, G; Popp, W; Gatol, H; Zwick, H

    1991-04-01

    An incremental cycle ergometer test performed with a total of 40 healthy subjects (25 male, 15 female) was used to study the mechanical load on the ventilatory muscles. The parameters for the mechanical load on the ventilatory muscles are the time integral of the oesophageal pressure and the mean oesophageal pressure change per time unit (dPoe/dTI) of each breathing manoeuvre. The pressure-time integral is the area delimited by the oesophageal pressure trace and the inspiratory time axis. It is expressed as a fraction of the product of the subject's maximum oesophageal pressure (Poe(max)) and total breath cycle duration (TTOT). This parameter is called oesophageal tension time index (TTIoe). The relationship between minute ventilation and these two parameters during ergometer test showed gender-specific variations because of the differences between men and women as to anthropometric data, lung function parameters and maximum ventilatory muscle strength. Moreover, the dPoe/dTI values significantly depend on the breathing frequency. The present study has provided evidence that, in general, the TTIoe and dPoe/dTI values in terms of a specific minute ventilation (VE) are higher in women than in men. Parameters for the mechanical load on the ventilatory muscles regarding the level of pressure to be generated as well as the duration and velocity of muscle contraction should therefore also allow for the gender of the patients.

  5. Reply to "Comment on 'Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle' ''.

    PubMed

    Abe, Sumiyoshi

    2015-05-01

    In their Comment on the paper [Abe and Okuyama, Phys. Rev. E 83, 021121 (2011)], González-Díaz and Díaz-Solórzano discuss that the initial state of the quantum-mechanical analog of the Carnot cycle should be not in a pure state but in a mixed state due to a projective measurement of the system energy. Here, first the Comment is shown to miss the point. Then, second, multiple projective measurements are discussed as a generalization of the Comment, although they are not relevant to the work commented.

  6. Action mechanisms of complementary and alternative medicine therapies for rheumatoid arthritis.

    PubMed

    Keisuke, Imada; Bian, Bao-lin; Li, Xiang-dong; Takashi, Sato; Akira, Ito

    2011-10-01

    Rheumatoid arthritis (RA) is characterized as a chronic inflammatory disease in joints and concomitant destruction of cartilage and bone. Cartilage extracellular matrix components, such as type II collagen and aggrecan are enzymatically degraded by matrix metalloproteinases (MMPs) and aggrecanases in RA. Currently, treatments targeting cytokines, including anti-tumor necrosis factor (TNF) α antibodies, soluble TNF receptor, anti-interleukin (IL)-6 receptor antibody, and IL-1 receptor antagonist, are widely used for treating RA in addition to antiantiinflammatory agents and disease-modifying antirheumatic drugs (DMARDs), such as inflmethotrexate, but these treatments have some problems, especially in terms of cost and the increased susceptibility of patients to infection in addition to the existence of low-responders to these treatments. Therefore, therapeutics that can be safely used for an extended period of time would be preferable. Complementary and alternative medicines including traditional Chinese medicines (TCM) have been used for the arthritic diseases through the ages. Recently, there are many reports concerning the anti-arthritic action mechanisms of TCM-based herbal formulas and crude herbal extracts or isolated ingredients. These natural herbal medicines are thought to moderately improve RA, but they exert various actions for the treatment of RA. In this review, the current status of the mechanism exploration of natural compounds and TCM-based herbal formulas are summarized, focusing on the protection of cartilage destruction in arthritic diseases including RA and osteoarthritis.

  7. Mass Spectrometric and Spectrophotometric Analyses Reveal an Alternative Structure and a New Formation Mechanism for Melanin.

    PubMed

    Li, Yuanjiao; Liu, Jingjing; Wang, Yajie; Chan, Ho Wai; Wang, Lianrong; Chan, Wan

    2015-08-01

    In this study, we investigated the formation mechanism and chemical structure of melanin that results from the self-assembly of L-3,4-dihydroxyphenylalanine (L-DOPA). Using a combination of "top-down" and "bottom-up" approaches, and on the basis of state-of-the-art electrospray ionization mass spectrometry (ESI-MS) results, we propose a new formation mechanism and an alternative structure for melanin. Specifically, our study of the self-aggregation of L-DOPA based on L-DOPA clusters revealed that melanin is comprised partially of noncovalent supramolecular aggregate that is formed by self-aggregation of L-DOPA and with the individual monomers linked together by a combination of hydrogen bonds, π-π stacking, and ionic bonds. Furthermore, our study showed that unmodified L-DOPA may be part of the building block for melanin in addition to the previously proposed indole derivative based on L-DOPA cyclization. A similar self-aggregation phenomenon was also observed in other structurally related catecholamines, for example, adrenaline.

  8. Hemp Thermal Insulation Concrete with Alternative Binders, Analysis of their Thermal and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Sinka, M.; Sahmenko, G.; Korjakins, A.; Radina, L.; Bajare, D.

    2015-11-01

    One of the main challenges that construction industry faces today is how to address the demands for more sustainable, environmentally friendly and carbon neutral construction materials and building upkeep processes. One of the answers to these demands is lime-hemp concrete (LHC) building materials - carbon negative materials that have sufficient thermal insulation capabilities to be used as thermal insulation materials for new as well as for existing buildings. But one problem needs to be overcome before these materials can be used on a large scale - current manufacturing technology allows these materials to be used only as self-bearing thermal insulation material with large labour intensity in the manufacturing process. In order to lower the labour intensity and allow the material to be used in wider applications, a LHC block and board production is necessary, which in turn calls for the binders different from the classically used ones, as they show insufficient mechanical strength for this new use. The particular study focuses on alternative binders produced using gypsum-cement compositions ensuring they are usable in outdoor applications together with hemp shives. Physical, mechanical, thermal and water absorption properties of hemp concrete with various binders are addressed in the current study.

  9. Global patterns and substrate-based mechanisms of the terrestrial nitrogen cycle.

    PubMed

    Niu, Shuli; Classen, Aimée T; Dukes, Jeffrey S; Kardol, Paul; Liu, Lingli; Luo, Yiqi; Rustad, Lindsey; Sun, Jian; Tang, Jianwu; Templer, Pamela H; Thomas, R Quinn; Tian, Dashuan; Vicca, Sara; Wang, Ying-Ping; Xia, Jianyang; Zaehle, Sönke

    2016-06-01

    Nitrogen (N) deposition is impacting the services that ecosystems provide to humanity. However, the mechanisms determining impacts on the N cycle are not fully understood. To explore the mechanistic underpinnings of N impacts on N cycle processes, we reviewed and synthesised recent progress in ecosystem N research through empirical studies, conceptual analysis and model simulations. Experimental and observational studies have revealed that the stimulation of plant N uptake and soil retention generally diminishes as N loading increases, while dissolved and gaseous losses of N occur at low N availability but increase exponentially and become the dominant fate of N at high loading rates. The original N saturation hypothesis emphasises sequential N saturation from plant uptake to soil retention before N losses occur. However, biogeochemical models that simulate simultaneous competition for soil N substrates by multiple processes match the observed patterns of N losses better than models based on sequential competition. To enable better prediction of terrestrial N cycle responses to N loading, we recommend that future research identifies the response functions of different N processes to substrate availability using manipulative experiments, and incorporates the measured N saturation response functions into conceptual, theoretical and quantitative analyses. PMID:26932540

  10. Global patterns and substrate-based mechanisms of the terrestrial nitrogen cycle.

    PubMed

    Niu, Shuli; Classen, Aimée T; Dukes, Jeffrey S; Kardol, Paul; Liu, Lingli; Luo, Yiqi; Rustad, Lindsey; Sun, Jian; Tang, Jianwu; Templer, Pamela H; Thomas, R Quinn; Tian, Dashuan; Vicca, Sara; Wang, Ying-Ping; Xia, Jianyang; Zaehle, Sönke

    2016-06-01

    Nitrogen (N) deposition is impacting the services that ecosystems provide to humanity. However, the mechanisms determining impacts on the N cycle are not fully understood. To explore the mechanistic underpinnings of N impacts on N cycle processes, we reviewed and synthesised recent progress in ecosystem N research through empirical studies, conceptual analysis and model simulations. Experimental and observational studies have revealed that the stimulation of plant N uptake and soil retention generally diminishes as N loading increases, while dissolved and gaseous losses of N occur at low N availability but increase exponentially and become the dominant fate of N at high loading rates. The original N saturation hypothesis emphasises sequential N saturation from plant uptake to soil retention before N losses occur. However, biogeochemical models that simulate simultaneous competition for soil N substrates by multiple processes match the observed patterns of N losses better than models based on sequential competition. To enable better prediction of terrestrial N cycle responses to N loading, we recommend that future research identifies the response functions of different N processes to substrate availability using manipulative experiments, and incorporates the measured N saturation response functions into conceptual, theoretical and quantitative analyses.

  11. Effects of Hygrothermal Cycling on the Chemical, Thermal, and Mechanical Properties of 862/W Epoxy Resin

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.; Roberts, Gary D.; Copa, Christine C.; Bail, Justin L.; Kohlman, Lee W.; Binienda, Wieslaw K.

    2011-01-01

    The hygrothermal aging characteristics of an epoxy resin were characterized over 1 year, which included 908 temperature and humidity cycles. The epoxy resin quickly showed evidence of aging through color change and increased brittleness. The influence of aging on the material s glass transition temperature (Tg) was evaluated by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The Tg remained relatively constant throughout the year long cyclic aging profile. The chemical composition was monitored by Fourier Transform Infrared Spectroscopy (FTIR) where evidence of chemical aging and advancement of cure was noted. The tensile strength of the resin was tested as it aged. This property was severely affected by the aging process in the form of reduced ductility and embrittlement. Detailed chemical evaluation suggests many aging mechanisms are taking place during exposure to hygrothermal conditions. This paper details the influence of processes such as: advancement of cure, chemical degradation, and physical aging on the chemical and physical properties of the epoxy resin.

  12. Understanding Low-cycle Fatigue Life Improvement Mechanisms in a Pre-twinned Magnesium Alloy

    SciTech Connect

    Wu, Wei; An, Ke

    2015-10-03

    The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning process, the removal of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress-strain hysteresis loop. The pre-twinning has significant impacts on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-deformed sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.

  13. Understanding Low-cycle Fatigue Life Improvement Mechanisms in a Pre-twinned Magnesium Alloy

    DOE PAGESBeta

    Wu, Wei; An, Ke

    2015-10-03

    The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning process, the removal of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress-strain hysteresis loop. The pre-twinning has significant impactsmore » on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-deformed sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.« less

  14. Life Cycle Assessment of mechanical biological pre-treatment of Municipal Solid Waste: a case study.

    PubMed

    Beylot, Antoine; Vaxelaire, Stéphane; Zdanevitch, Isabelle; Auvinet, Nicolas; Villeneuve, Jacques

    2015-05-01

    The environmental performance of mechanical biological pre-treatment (MBT) of Municipal Solid Waste is quantified using Life Cycle Assessment (LCA), considering one of the 57 French plants currently in operation as a case study. The inventory is mostly based on plant-specific data, extrapolated from on-site measurements regarding mechanical and biological operations (including anaerobic digestion and composting of digestate). The combined treatment of 46,929 tonnes of residual Municipal Solid Waste and 12,158 tonnes of source-sorted biowaste (as treated in 2010 at the plant) generates 24,550 tonnes CO2-eq as an impact on climate change, 69,943kg SO2-eq on terrestrial acidification and 19,929kg NMVOC-eq on photochemical oxidant formation, in a life-cycle perspective. On the contrary MBT induces environmental benefits in terms of fossil resource depletion, human toxicity (carcinogenic) and ecotoxicity. The results firstly highlight the relatively large contribution of some pollutants, such as CH4, emitted at the plant and yet sometimes neglected in the LCA of waste MBT. Moreover this study identifies 4 plant-specific operation conditions which drive the environmental impact potentials induced by MBT: the conditions of degradation of the fermentable fraction, the collection of gaseous flows emitted from biological operations, the abatement of collected pollutants and NOx emissions from biogas combustion. Finally the results underline the relatively large influence of the operations downstream the plant (in particular residuals incineration) on the environmental performance of waste MBT.

  15. Cancer cell(s) cycle sequencing reveals universal mechanisms of apoptosis.

    PubMed

    Marretta, R M Ardito; Ales, F

    2010-12-01

    In this paper, cell cycle in higher eukaryotes and their molecular networks signals both in G1/S and G2/M transitions are replicated in silico. Biochemical kinetics, converted into a set of differential equations, and system control theory are employed to design multi-nested digital layers to simulate protein-to-protein activation and inhibition for cell cycle dynamics in the presence of damaged genomes. Sequencing and controlling the digital process of four micro-scale species networks (p53/Mdm2/DNA damage, p21mRNA/cyclin-CDK complex, CDK/CDC25/weel/SKP2/APC/CKI and apoptosis target genes system) not only allows the comprehension of the mechanisms of these molecule interactions but paves the way for unraveling the participants and their by-products, until now quite unclear, which have the task of carrying out (or not) cell death. Whatever the running simulations (e.g., different species signals, mutant cells and different DNA damage levels), the results of the proposed cell digital multi-layers give reason to believe in the existence of a universal apoptotic mechanism. As a consequence, we identified and selected cell check points, sizers, timers and specific target genes dynamic both for influencing mitotic process and avoiding cancer proliferation as much as for leading the cancer cell(s) to collapse into a steady stable apoptosis phase. PMID:21141676

  16. Microbial mechanisms coupling carbon and phosphorus cycles in phosphorus-limited northern Adriatic Sea.

    PubMed

    Malfatti, F; Turk, V; Tinta, T; Mozetič, P; Manganelli, M; Samo, T J; Ugalde, J A; Kovač, N; Stefanelli, M; Antonioli, M; Fonda-Umani, S; Del Negro, P; Cataletto, B; Hozić, A; Ivošević Denardis, N; Zutić, V; Svetličić, V; Mišić Radić, T; Radić, T; Fuks, D; Azam, F

    2014-02-01

    The coastal northern Adriatic Sea receives pulsed inputs of riverine nutrients, causing phytoplankton blooms and seasonally sustained dissolved organic carbon (DOC) accumulation-hypothesized to cause episodes of massive mucilage. The underlying mechanisms regulating P and C cycles and their coupling are unclear. Extensive biogeochemical parameters, processes and community composition were measured in a 64-day mesocosms deployed off Piran, Slovenia. We followed the temporal trends of C and P fluxes in P-enriched (P+) and unenriched (P-) mesocosms. An intense diatom bloom developed then crashed; however, substantial primary production was maintained throughout, supported by tightly coupled P regeneration by bacteria and phytoplankton. Results provide novel insights on post-bloom C and P dynamics and mechanisms. 1) Post-bloom DOC accumulation to 186 μM remained elevated despite high bacterial carbon demand. Presumably, a large part of DOC accumulated due to the bacterial ectohydrolytic processing of primary productivity that adventitiously generated slow-to-degrade DOC; 2) bacteria heavily colonized post-bloom diatom aggregates, rendering them microscale hotspots of P regeneration due to locally intense bacterial ectohydrolase activities; 3) Pi turnover was rapid thus suggesting high P flux through the DOP pool (dissolved organic phosphorus) turnover; 4) Alpha- and Gamma-proteobacteria dominated the bacterial communities despite great differences of C and P pools and fluxes in both mesocosms. However, minor taxa showed dramatic changes in community compositions. Major OTUs were presumably generalists adapted to diverse productivity regimes.We suggest that variation in bacterial ectohydrolase activities on aggregates, regulating the rates of POM→DOM transition as well as dissolved polymer hydrolysis, could become a bottleneck in P regeneration. This could be another regulatory step, in addition to APase, in the microbial regulation of P cycle and the coupling

  17. Compensatory mechanisms in Great Lakes sea lamprey populations: implications for alternative control strategies

    USGS Publications Warehouse

    Jones, Michael L.; Bergstedt, R.A.; Twohey, Michael B.; Fodale, Michael F.; Cuddy, Douglas W.; Slade, Jeffrey W.

    2003-01-01

    Compensatory mechanisms are demographic processes that tend to increase population growth rates at lower population density. These processes will tend to reduce the effectiveness of actions that use controls on reproductive success to suppress sea lamprey (Petromyzon marinus), an economically important pest in the Great Lakes. Historical evidence for compensatory mechanisms in sea lamprey populations was reviewed, and revealed: (1) strong evidence for shifts in sex ratios as sea lamprey abundance was reduced in the early years of the control program; (2) weak and equivocal evidence for increased growth rates of sea lamprey cohorts re-colonizing streams following a lampricide treatment; and (3) suggestions of other compensatory processes, such as earlier ages at metamorphosis, but with little empirical evidence. Larval size distribution data for cohorts in the first and second years following a lampricide treatment (26 pairs of cohorts in 20 streams) was analyzed and did not indicate a consistent pattern of more rapid growth of the first colonizing cohort (only 11 of 33 cases). To test for compensation between spawning and age-1 in sea lamprey populations, data were analyzed for 49 stream-years for which spawning female abundance was known and age-1 abundance was estimated in the following year. A fit of these data to a Ricker stock-recruitment function showed evidence for compensation, measured as reduced survival to age 1 at higher abundance of spawning females. More obvious, however, was a large amount of density-independent variation in survival, which tends to mask evidence for compensatory survival. The results were applied to a simple model that simulates sea lamprey populations and their control in a hypothetical lake. Control strategies that targeted reproductive success performed far less well than comparable strategies that targeted larval populations, because density-independent recruitment variation leads to occasional strong year classes even when

  18. Investigation into the effects of varying frequency of mechanical stimulation in a cycle-by-cycle manner on engineered cardiac construct function.

    PubMed

    Morgan, Kathy Ye; Black, Lauren Deems

    2014-06-11

    Mechanical stimulation has been used extensively to improve the function of cardiac engineered tissue, as it mimics the physical environment in which the tissue is situated during normal development. However, previous mechanical stimulation has been carried out under a constant frequency that more closely resembles a diseased heart. The goal of this study was to create a bioreactor system that would allow us to control the mechanical stimulation of engineered cardiac tissue on a cycle-by-cycle basis. This unique system allows us to determine the effects on cardiac construct function of introducing variability to the mechanical stretch. To test our bioreactor system, constructs created from neonatal rat cardiomyocytes entrapped in fibrin hydrogels were stimulated under various regimes for 2 weeks and then assessed for functional outcomes. No differences were observed in the final cell number in each condition, indicating that variability in frequency did not have a negative effect on viability. The forces were higher for all mechanical stimulation groups compared to static controls, although no differences were observed between the mechanically stimulated conditions, indicating that variable frequency on a cycle-by-cycle basis has limited effects on the resulting force. Although differences in the observed twitch force were not observed, differences in the protein expression indicate that variable-frequency mechanical stimulation had an effect on cell-cell coupling and growth pathway activation in the constructs. Thus, this bioreactor system provides a valuable tool for further development and optimization of engineered myocardial tissue as a repair or replacement strategy for patients undergoing heart failure. Copyright © 2014 John Wiley & Sons, Ltd.

  19. A comparative study of commercial lithium ion battery cycle life in electrical vehicle: Aging mechanism identification

    NASA Astrophysics Data System (ADS)

    Han, Xuebing; Ouyang, Minggao; Lu, Languang; Li, Jianqiu; Zheng, Yuejiu; Li, Zhe

    2014-04-01

    When lithium-ion batteries age with cycling, the battery capacity decreases and the resistance increases. The aging mechanism of different types of lithium-ion batteries differs. The loss of lithium inventory, loss of active material, and the increase in resistance may result in battery aging. Generally, analysis of the battery aging mechanism requires dismantling of batteries and using methods such as X-ray diffraction and scanning electron microscopy. These methods may permanently damage the battery. Therefore, the methods are inappropriate for the battery management system (BMS) in an electric vehicle. The constant current charging curves while charging the battery could be used to get the incremental capacity and differential voltage curves for identifying the aging mechanism; the battery state-of-health can then be estimated. This method can be potentially used in the BMS for online diagnostic and prognostic services. The genetic algorithm could be used to quantitatively analyze the battery aging offline. And the membership function could be used for onboard aging mechanism identification.

  20. Differing mechanisms in the CO2 seasonal cycle and its amplitude change

    NASA Astrophysics Data System (ADS)

    Zeng, N.; Zhao, F.

    2015-12-01

    The net terrestrial carbon flux to the atmosphere simulated by nine TRENDY models during 1961-2012 are examined on its mean seasonal cycle and seasonal amplitude increase. While the model ensemble agree well with observations on both the trend and latitudinal pattern of flux seasonal amplitude, notable model spread is evident. Further analyses using results from TRENDY's sensitivity experiments highlight important underlying difference in mechanisms responsible for the similar amplitude increase simulated by the models. We found that CO2 fertilization effect is the prevailing mechanism for amplitude increase of net carbon flux in seven out of nine models. Models disagree on the effect of climate: even though high latitude warming contribute to a major part of amplitude increase over the boreal region in two thirds of the models, this positive impact is largely negated by the negative influence over the temperate region and the tropics, possibly related to droughts that lowered the productivity of ecosystem during peak growing season. The effect of land use plays a significant positive role in five out of the nine models, however few model is able to simulate mechanisms such as improved farming practice and crop selection. Our results suggest that using model ensemble only may hide important mechanisms from individual model.

  1. Dunaliella tertiolecta (Chlorophyta) Avoids Cell Death Under Ultraviolet Radiation By Triggering Alternative Photoprotective Mechanisms.

    PubMed

    Segovia, María; Mata, Teresa; Palma, Armando; García-Gómez, Candela; Lorenzo, Rosario; Rivera, Alicia; Figueroa, Félix L

    2015-11-01

    The effect of different ultraviolet radiation (UVR) treatments combining PAR (P), UVA (A) and UVB (B) on the molecular physiology of Dunaliella tertiolecta was studied during 6 days to assess the response to chronic UVR exposure. UVR reduced cell growth but did not cause cell death, as shown by the absence of SYTOX Green labeling and cellular morphology. However, caspase-like enzymatic activities (CLs), (regarded as cell death proteases), were active even though the cells were not dying. Maximal quantum yield of fluorescence (Fv /Fm ) and photosynthetic electron transport rate (ETR) dropped. Decreased nonphotochemical quenching (NPQ) paralleled a drop in xanthophyll cycle de-epoxidation under UVB. Reactive oxygen species (ROS) and D1 protein accumulation were inversely correlated. PAB exhibited elevated ROS production at earlier times. Once ROS decayed, D1 protein recovered two-fold compared with P and PA at later stages. Therefore, PsbA gene was still transcribed, suggesting ROS involvement in D1 recovery by its direct effect on mRNA-translation. We add evidence of an UVB-induced positive effect on the cells when P is present, providing photoprotection and resilience, by means of D1 repair. This allowed cells to survive. The photoprotective mechanisms described here (which are counterintuitive in principle) conform to an important ecophysiological response regarding light stress acclimation.

  2. Dunaliella tertiolecta (Chlorophyta) Avoids Cell Death Under Ultraviolet Radiation By Triggering Alternative Photoprotective Mechanisms.

    PubMed

    Segovia, María; Mata, Teresa; Palma, Armando; García-Gómez, Candela; Lorenzo, Rosario; Rivera, Alicia; Figueroa, Félix L

    2015-11-01

    The effect of different ultraviolet radiation (UVR) treatments combining PAR (P), UVA (A) and UVB (B) on the molecular physiology of Dunaliella tertiolecta was studied during 6 days to assess the response to chronic UVR exposure. UVR reduced cell growth but did not cause cell death, as shown by the absence of SYTOX Green labeling and cellular morphology. However, caspase-like enzymatic activities (CLs), (regarded as cell death proteases), were active even though the cells were not dying. Maximal quantum yield of fluorescence (Fv /Fm ) and photosynthetic electron transport rate (ETR) dropped. Decreased nonphotochemical quenching (NPQ) paralleled a drop in xanthophyll cycle de-epoxidation under UVB. Reactive oxygen species (ROS) and D1 protein accumulation were inversely correlated. PAB exhibited elevated ROS production at earlier times. Once ROS decayed, D1 protein recovered two-fold compared with P and PA at later stages. Therefore, PsbA gene was still transcribed, suggesting ROS involvement in D1 recovery by its direct effect on mRNA-translation. We add evidence of an UVB-induced positive effect on the cells when P is present, providing photoprotection and resilience, by means of D1 repair. This allowed cells to survive. The photoprotective mechanisms described here (which are counterintuitive in principle) conform to an important ecophysiological response regarding light stress acclimation. PMID:26224653

  3. Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    This report presents the results of both the fifth and sixth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA). The research included on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for five variables, namely, high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of high-cycle mechanical

  4. Climate change and shrinking salamanders: alternative mechanisms for changes in plethodontid salamander body size.

    PubMed

    Connette, Grant M; Crawford, John A; Peterman, William E

    2015-08-01

    An increasing number of studies have demonstrated relationships between climate trends and body size change of organisms. In many cases, climate might be expected to influence body size by altering thermoregulation, energetics or food availability. However, observed body size change can result from a variety of ecological processes (e.g. growth, selection, population dynamics) or imperfect observation of biological systems. We used two extensive datasets to evaluate alternative mechanisms for recently reported changes in the observed body size of plethodontid salamanders. We found that mean adult body size of salamanders can be highly sensitive to survey conditions, particularly rainfall. This systematic bias in the detection of larger or smaller individuals could result in a signature of body size change in relation to reported climate trends when it is simply observation error. We also identify considerable variability in body size distributions among years and find that individual growth rates can be strongly influenced by weather. Finally, our study demonstrates that measures of mean adult body size can be highly variable among surveys and that large sample sizes may be required to make reliable inferences. Identifying the effects of climate change is a critical area of research in ecology and conservation. Researchers should be aware that observed changes in certain organisms can result from multiple ecological processes or systematic bias due to nonrandom sampling of populations.

  5. Climate change and shrinking salamanders: alternative mechanisms for changes in plethodontid salamander body size.

    PubMed

    Connette, Grant M; Crawford, John A; Peterman, William E

    2015-08-01

    An increasing number of studies have demonstrated relationships between climate trends and body size change of organisms. In many cases, climate might be expected to influence body size by altering thermoregulation, energetics or food availability. However, observed body size change can result from a variety of ecological processes (e.g. growth, selection, population dynamics) or imperfect observation of biological systems. We used two extensive datasets to evaluate alternative mechanisms for recently reported changes in the observed body size of plethodontid salamanders. We found that mean adult body size of salamanders can be highly sensitive to survey conditions, particularly rainfall. This systematic bias in the detection of larger or smaller individuals could result in a signature of body size change in relation to reported climate trends when it is simply observation error. We also identify considerable variability in body size distributions among years and find that individual growth rates can be strongly influenced by weather. Finally, our study demonstrates that measures of mean adult body size can be highly variable among surveys and that large sample sizes may be required to make reliable inferences. Identifying the effects of climate change is a critical area of research in ecology and conservation. Researchers should be aware that observed changes in certain organisms can result from multiple ecological processes or systematic bias due to nonrandom sampling of populations. PMID:25641384

  6. Hydroxyl radical generation mechanism during the redox cycling process of 1,4-naphthoquinone.

    PubMed

    Shang, Yu; Chen, Chenyong; Li, Yi; Zhao, Jincai; Zhu, Tong

    2012-03-01

    Airborne quinones contribute to adverse health effects of ambient particles probably because of their ability to generate hydroxyl radicals (·OH) via redox cycling, but the mechanisms remain unclear. We examined the chemical mechanisms through which 1,4-naphthoquinone (1,4-NQ) induced ·OH, and the redox interactions between 1,4-NQ and ascorbate acid (AscH(2)). First, ·OH formation by 1,4-NQ was observed in cellular and acellular systems, and was enhanced by AscH(2). AscH(2) also exacerbated the cytotoxicity of 1,4-NQ in Ana-1 macrophages, at least partially due to enhanced ·OH generation. The detailed mechanism was studied in an AscH(2)/H(2)O(2) physiological system. The existence of a cyclic 1,4-NQ process was shown by detecting the corresponding semiquinone radical (NSQ·-) and hydroquinone (NQH(2)). 1,4-NQ was reduced primarily to NSQ·- by O2·- (which was from AscH(2) reacting with H(2)O(2)), not by AscH(2) as normally thought. At lower doses, 1,4-NQ consumed O2·- to suppress ·OH; however, at higher doses, 1,4-NQ presented a positive association with ·OH. The reaction of NSQ·- with H(2)O(2) to release ·OH was another important channel for OH radical formation except for Haber-Weiss reaction. As a reaction precursor for O2·-, the enhanced ·OH response to 1,4-NQ by AscH(2) was indirect. Reducing substrates were necessary to sustain the redox cycling of 1,4-NQ, leading to more ·OH and a deleterious end point.

  7. [Alternative Splicing Detection as a Biomarker for Cancer Diagnosis: A Novel Progressive Mechanism of Acute Lymphoblastic Leukemia with Alternative Splicing as a Biomarker Candidate].

    PubMed

    Kitamura, Kouichi; Matsushita, Kazuyuki; Kobayashi, Souhei; Ishige, Takayuki; Semba, Toshihisa; Kimura, Asako; Kazami, Takahiro; Ohyama, Masayuki; Itoga, Sakae; Beppu, Minako; Nishimura, Motoi; Satoh, Mamoru; Nomura, Fumio

    2015-09-01

    Alternative splicing is an important mechanism that links to transcription and contributes to protein diversity. Disturbed alternative splicing is frequently observed in cancers, but its precise mechanism remains largely unknown. FUSE-binding protein (FBP) -interacting repressor (FIR) is a transcriptional repressor of the c-myc gene. Previous studies indicated that a splice variant of FIR, FIRΔexon2, that lacks exon2 in the transcriptional repressor domain, was increased in colorectal cancers, hepatocellular carcinomas, and leukemia cells. Furthermore, FIRΔexon2 activated c-myc transcription by disabling wild-type FIR as a dominant-negative form of FIR. Recently, somatic mutations of the SF3B1 (SAP155) gene, a subunit of the SF3B spliceosome complex, were found in myelodysplastic leukemia. In this study, FIR heterozygous knockout (FIR(+/-)) was established as a dominant-negative model of FIR in the C57BL/6 mouse. FIR(+/-) mice showed an increased c-myc mRNA expression level, particularly in peripheral blood, although FIR(+/-) mice had no apparent pathogenic phenotype. Therefore, an increased c-myc mRNA expression level alone is not enough for leukemogenesis. Nevertheless, FIR(+/-)TP53(-/-) mice generated acute T-cell lymphoblastic leukemia (T-ALL) with increased organ and/or bone marrow invasion. In conclusion, alternative splicing of FIR, generating FIRΔexon2, contributes to not only colorectal carcinogenesis but also leukemogenesis independent of the c-Myc activation pathway. Finally, we will discuss our hypothesis that FIRΔexon2 interferes with FBW7, that FIRΔexon2 inhibits PP1 in the EGFR pathway, and that FIR haploinsufficiency is potentially associated with protein expression through transcriptional and post-transcriptional mechanisms. PMID:26731899

  8. The water-water cycle in leaves is not a major alternative electron sink for dissipation of excess excitation energy when CO(2) assimilation is restricted.

    PubMed

    Driever, Steven M; Baker, Neil R

    2011-05-01

    Electron flux from water via photosystem II (PSII) and PSI to oxygen (water-water cycle) may provide a mechanism for dissipation of excess excitation energy in leaves when CO(2) assimilation is restricted. Mass spectrometry was used to measure O(2) uptake and evolution together with CO(2) uptake in leaves of French bean and maize at CO(2) concentrations saturating for photosynthesis and the CO(2) compensation point. In French bean at high CO(2) and low O(2) concentrations no significant water-water cycle activity was observed. At the CO(2) compensation point and 3% O(2) a low rate of water-water cycle activity was observed, which accounted for 30% of the linear electron flux from water. In maize leaves negligible water-water cycle activity was detected at the compensation point. During induction of photosynthesis in maize linear electron flux was considerably greater than CO(2) assimilation, but no significant water-water cycle activity was detected. Miscanthus × giganteus grown at chilling temperature also exhibited rates of linear electron transport considerably in excess of CO(2) assimilation; however, no significant water-water cycle activity was detected. Clearly the water-water cycle can operate in leaves under some conditions, but it does not act as a major sink for excess excitation energy when CO(2) assimilation is restricted.

  9. Thermo-mechanical effects of thermal cycled copper through-silicon vias

    NASA Astrophysics Data System (ADS)

    Marro, James

    The semiconductor industry is currently facing transistor scaling issues due to fabrication thresholds and quantum effects. In this "More-Than-Moore" era, the industry is developing new ways to increase device performance, such as stacking chips for three-dimensional integrated circuits (3D-IC). The 3D-IC's superior performance over their 2D counterparts can be attributed to the use of vertical interconnects, or through silicon vias (TSV). These interconnects are much shorter, reducing signal delay. However TSVs are susceptible to various thermo-mechanical reliability concerns. Heating during fabrication and use, in conjunction with coefficient of thermal expansion mismatch between the copper TSVs and silicon substrate, create harmful stresses in the system. The purpose of this work is to evaluate the signal integrity of Cu-TSVs and determine the major contributing factors of the signal degradation upon in-use conditions. Two series of samples containing blind Cu-TSVs embedded in a Si substrate were studied, each having different types and amounts of voids from manufacturing. The samples were thermally cycled up to 2000 times using three maximum temperatures to simulate three unique in-use conditions. S11 parameter measurements were then conducted to determine the signal integrity of the TSVs. To investigate the internal response from cycling, a protocol was developed for cross-sectioning the copper TSVs. Voids were measured using scanning electron microscope and focused ion beam imaging of the cross-sections, while the microstructural evolution of the copper was monitored with electron backscattering diffraction. An increase in void area was found to occur after cycling. This is thought to be the major contributing factor in the signal degradation of the TSVs, since no microstructural changes were observed in the copper.

  10. Classical and quantum-mechanical treatments of nonsequential double ionization with few-cycle laser pulses

    NASA Astrophysics Data System (ADS)

    Figueira de Morisson Faria, C.; Liu, X.; Sanpera, A.; Lewenstein, M.

    2004-10-01

    We address nonsequential double ionization induced by strong, linearly polarized laser fields of only a few cycles, considering a physical mechanism in which the second electron is dislodged by the inelastic collision of the first electron with its parent ion. The problem is treated classically, using an ensemble model, and quantum mechanically, within the strong-field and uniform saddle-point approximations. In the latter case, the results are interpreted in terms of “quantum orbits,” which can be related to the trajectories of a classical electron in an electric field. We obtain highly asymmetric electron momentum distributions, which strongly depend on the absolute phase, i.e., on the phase difference between the pulse envelope and its carrier frequency. Around a particular value of this parameter, the distributions shift from the region of positive to that of negative momenta, or vice versa, in a radical fashion. This behavior is investigated in detail for several driving-field parameters, and provides a very efficient method for measuring the absolute phase. Both models yield very similar distributions, which share the same physical explanation. There exist, however, minor discrepancies due to the fact that, beyond the region for which electron-impact ionization is classically allowed, the yields from the quantum-mechanical computation decay exponentially, whereas their classical counterparts vanish.

  11. Mechanisms and concepts paving the way towards a complete transport cycle of plant vacuolar sorting receptors.

    PubMed

    De Marcos Lousa, Carine; Gershlick, David C; Denecke, Jurgen

    2012-05-01

    Delivery of proteins to the lytic vacuole in plants is a complex cascade of selective interactions that specifically excludes residents of the endoplasmic reticulum and secreted proteins. Vacuolar transport must be highly efficient to avoid mistargeting of hydrolytic enzymes to locations where they could be harmful. While plant vacuolar sorting signals have been well described for two decades, it is only during the last 5 years that a critical mass of data was gathered that begins to reveal how vacuolar sorting receptors (VSRs) may complete a full transport cycle. Yet, the field is far from reaching a consensus regarding the organelles that could be involved in vacuolar sorting, their potential biogenesis, and the ultimate recycling of membranes and protein machinery that maintain this pathway. This review will highlight the important landmarks in our understanding of VSR function and compare recent transport models that have been proposed so that an emerging picture of plant vacuolar sorting mechanisms can be drawn. PMID:22570446

  12. MECHANISMS IN ENDOCRINOLOGY: Alternative splicing: the new frontier in diabetes research.

    PubMed

    Juan-Mateu, Jonàs; Villate, Olatz; Eizirik, Décio L

    2016-05-01

    Type 1 diabetes (T1D) is a chronic autoimmune disease in which pancreatic β cells are killed by infiltrating immune cells and by cytokines released by these cells. This takes place in the context of a dysregulated dialogue between invading immune cells and target β cells, but the intracellular signals that decide β cell fate remain to be clarified. Alternative splicing (AS) is a complex post-transcriptional regulatory mechanism affecting gene expression. It regulates the inclusion/exclusion of exons into mature mRNAs, allowing individual genes to produce multiple protein isoforms that expand the proteome diversity. Functionally related transcript populations are co-ordinately spliced by master splicing factors, defining regulatory networks that allow cells to rapidly adapt their transcriptome in response to intra and extracellular cues. There is a growing interest in the role of AS in autoimmune diseases, but little is known regarding its role in T1D. In this review, we discuss recent findings suggesting that splicing events occurring in both immune and pancreatic β cells contribute to the pathogenesis of T1D. Splicing switches in T cells and in lymph node stromal cells are involved in the modulation of the immune response against β cells, while β cells exposed to pro-inflammatory cytokines activate complex splicing networks that modulate β cell viability, expression of neoantigens and susceptibility to immune-induced stress. Unveiling the role of AS in β cell functional loss and death will increase our understanding of T1D pathogenesis and may open new avenues for disease prevention and therapy. PMID:26628584

  13. Structural basis of the alternating-access mechanism in a bile acid transporter

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoming; Levin, Elena J.; Pan, Yaping; McCoy, Jason G.; Sharma, Ruchika; Kloss, Brian; Bruni, Renato; Quick, Matthias; Zhou, Ming

    2014-01-01

    Bile acids are synthesized from cholesterol in hepatocytes and secreted through the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for resecretion. In humans, there are two Na+-dependent bile acid transporters involved in enterohepatic recirculation, the Na+-taurocholate co-transporting polypeptide (NTCP; also known as SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT; also known as SLC10A2) expressed on enterocytes in the terminal ileum. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolaemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. However, a lack of three-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data. The crystal structure of an ASBT homologue from Neisseria meningitidis (ASBTNM) in detergent was reported recently, showing the protein in an inward-open conformation bound to two Na+ and a taurocholic acid. However, the structural changes that bring bile acid and Na+ across the membrane are difficult to infer from a single structure. To understand the structural changes associated with the coupled transport of Na+ and bile acids, here we solved two structures of an ASBT homologue from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives the conserved `crossover' region, where two discontinuous helices cross each other, alternating accessibility from either side of the cell membrane. This result has implications

  14. tLivin Displays Flexibility by Promoting Alternative Cell Death Mechanisms

    PubMed Central

    Shiloach, Tamar; Berens, Christian; Danke, Christina; Waiskopf, Ortal; Perlman, Riki; Ben-Yehuda, Dina

    2014-01-01

    Livin is a member of the Inhibitor of Apoptosis (IAP) protein family that inhibits apoptosis triggered by a variety of stimuli. We previously demonstrated that while Livin inhibits caspase activity, caspases can cleave Livin to produce a truncated protein, tLivin and that this newly formed tLivin paradoxically induces cell death. However to date, the mechanism of tLivin-induced cell death is not fully understood. In this study, we set out to characterize the form of cell death mediated by tLivin. Here we demonstrate that, unlike most death-promoting proteins, tLivin is a flexible inducer of cell death capable of promoting necrosis or apoptosis in different cell lines. The unusual flexibility of tLivin is displayed by its ability to activate an alternative form of cell death when apoptosis is inhibited. Thus, tLivin can promote more than one form of cell death in the same cell type. Interestingly, in cells where tLivin induces necrosis, deletion of the caspase binding BIR domain results in tLivin-induced apoptosis, suggesting the BIR domain can potentially hamper the ability of tLivin to induce apoptosis. We further elucidate that tLivin activates the JNK pathway and both tLivin-induced apoptosis and necrosis are partially mediated by JNK activity. Acquired resistance to apoptosis, common in many tumors, impinges on the efficiency of conventional anti-cancer agents that function primarily by inducing apoptosis. The ability of tLivin to induce death of apoptosis-compromised cells makes it an attractive candidate for targeted cancer therapy. PMID:24960127

  15. Alternative mechanism of activation of the epithelial na+ channel by cleavage.

    PubMed

    Hu, John Cong; Bengrine, Abderrahmane; Lis, Agnieszka; Awayda, Mouhamed S

    2009-12-25

    We examined activation of the human epithelial sodium channel (ENaC) by cleavage. We focused on cleavage of alphaENaC using the serine protease subtilisin. Trimeric channels formed with alphaFM, a construct with point mutations in both furin cleavage sites (R178A/R204A), exhibited marked reduction in spontaneous cleavage and an approximately 10-fold decrease in amiloride-sensitive whole cell conductance as compared with alphaWT (2.2 versus 21.2 microsiemens (microS)). Both alphaWT and alphaFM were activated to similar levels by subtilisin cleavage. Channels formed with alphaFD, a construct that deleted the segment between the two furin sites (Delta175-204), exhibited an intermediate conductance of 13.2 microS. More importantly, alphaFD retained the ability to be activated by subtilisin to 108.8 +/- 20.9 microS, a level not significantly different from that of subtilisin activated alphaWT (125.6 +/- 23.9). Therefore, removal of the tract between the two furin sites is not the main mechanism of channel activation. In these experiments the levels of the cleaved 22-kDa N-terminal fragment of alpha was low and did not match those of the C-terminal 65-kDa fragment. This indicated that cleavage may activate ENaC by the loss of the smaller fragment and the first transmembrane domain. This was confirmed in channels formed with alphaLD, a construct that extended the deleted sequence of alphaFD by 17 amino acids (Delta175-221). Channels with alphaLD were uncleaved, exhibited low baseline activity (4.1 microS), and were insensitive to subtilisin. Collectively, these data support an alternative hypothesis of ENaC activation by cleavage that may involve the loss of the first transmembrane domain from the channel complex. PMID:19858199

  16. Confidence versus Performance as an Indicator of the Presence of Alternative Conceptions and Inadequate Problem-Solving Skills in Mechanics

    ERIC Educational Resources Information Center

    Potgieter, Marietjie; Malatje, Esther; Gaigher, Estelle; Venter, Elsie

    2010-01-01

    This study investigated the use of performance-confidence relationships to signal the presence of alternative conceptions and inadequate problem-solving skills in mechanics. A group of 33 students entering physics at a South African university participated in the project. The test instrument consisted of 20 items derived from existing standardised…

  17. CuCrZr alloy microstructure and mechanical properties after hot isostatic pressing bonding cycles

    NASA Astrophysics Data System (ADS)

    Frayssines, P.-E.; Gentzbittel, J.-M.; Guilloud, A.; Bucci, P.; Soreau, T.; Francois, N.; Primaux, F.; Heikkinen, S.; Zacchia, F.; Eaton, R.; Barabash, V.; Mitteau, R.

    2014-04-01

    ITER first wall (FW) panels are a layered structure made of the three following materials: 316L(N) austenitic stainless steel, CuCrZr alloy and beryllium. Two hot isostatic pressing (HIP) cycles are included in the reference fabrication route to bond these materials together for the normal heat flux design supplied by the European Union (EU). This reference fabrication route ensures sufficiently good mechanical properties for the materials and joints, which fulfil the ITER mechanical specifications, but often results in a coarse grain size for the CuCrZr alloy, which is not favourable, especially, for the thermal creep properties of the FW panels. To limit the abnormal grain growth of CuCrZr and make the ITER FW fabrication route more reliable, a study began in 2010 in the EU in the frame of an ITER task agreement. Two material fabrication approaches have been investigated. The first one was dedicated to the fabrication of solid CuCrZr alloy in close collaboration with an industrial copper alloys manufacturer. The second approach investigated was the manufacturing of CuCrZr alloy using the powder metallurgy (PM) route and HIP consolidation. This paper presents the main mechanical and microstructural results associated with the two CuCrZr approaches mentioned above. The mechanical properties of solid CuCrZr, PM CuCrZr and joints (solid CuCrZr/solid CuCrZr and solid CuCrZr/316L(N) and PM CuCrZr/316L(N)) are also presented.

  18. Application of fracture mechanics and half-cycle theory to the prediction of fatigue life of aerospace structural components

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1989-01-01

    The service life of aircraft structural components undergoing random stress cycling was analyzed by the application of fracture mechanics. The initial crack sizes at the critical stress points for the fatigue crack growth analysis were established through proof load tests. The fatigue crack growth rates for random stress cycles were calculated using the half-cycle method. A new equation was developed for calculating the number of remaining flights for the structural components. The number of remaining flights predicted by the new equation is much lower than that predicted by the conventional equation. This report describes the application of fracture mechanics and the half-cycle method to calculate the number of remaining flights for aircraft structural components.

  19. Supercharged two-cycle engines employing novel single element reciprocating shuttle inlet valve mechanisms and with a variable compression ratio

    NASA Technical Reports Server (NTRS)

    Wiesen, Bernard (Inventor)

    2008-01-01

    This invention relates to novel reciprocating shuttle inlet valves, effective with every type of two-cycle engine, from small high-speed single cylinder model engines, to large low-speed multiple cylinder engines, employing spark or compression ignition. Also permitting the elimination of out-of-phase piston arrangements to control scavenging and supercharging of opposed-piston engines. The reciprocating shuttle inlet valve (32) and its operating mechanism (34) is constructed as a single and simple uncomplicated member, in combination with the lost-motion abutments, (46) and (48), formed in a piston skirt, obviating the need for any complex mechanisms or auxiliary drives, unaffected by heat, friction, wear or inertial forces. The reciprocating shuttle inlet valve retains the simplicity and advantages of two-cycle engines, while permitting an increase in volumetric efficiency and performance, thereby increasing the range of usefulness of two-cycle engines into many areas that are now dominated by the four-cycle engine.

  20. Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

    SciTech Connect

    Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce; Hall, David; Niaz, Iftikhar Ahmad; Zhou, Yuchun; Sham, L. J.; Lo, Yu-Hwa

    2015-08-03

    Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanism based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.

  1. Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 2: Advanced energy conversion systems. Part 1: Open-cycle gas turbines

    NASA Technical Reports Server (NTRS)

    Brown, D. H.; Corman, J. C.

    1976-01-01

    Ten energy conversion systems are defined and analyzed in terms of efficiency. These include: open-cycle gas turbine recuperative; open-cycle gas turbine; closed-cycle gas turbine; supercritical CO2 cycle; advanced steam cycle; liquid metal topping cycle; open-cycle MHD; closed-cycle inert gas MHD; closed-cycle liquid metal MHD; and fuel cells. Results are presented.

  2. Mechanism for synchronized motion between two humans in mutual tapping experiments: transition from alternative mode to synchronization mode.

    PubMed

    Hayashi, Yoshikatsu; Kondo, Toshiyuki

    2013-08-01

    We performed mutual tapping experiments between two humans to investigate the conditions required for synchronized motion. A transition from an alternative mode to a synchronization mode was discovered under the same conditions as when a subject changed from a reactive mode to an anticipation mode in single tapping experiments. The experimental results suggest that the cycle time for each tapping motion is tuned by a proportional control that is based on synchronization errors and cycle time errors. As the tapping frequency increases, a mathematical model based on feedback control in the sensory-motor closed loop predicts a discrete transition of the mode as the gain factors of the proportional control decrease. The conditions for synchronization are shown as a consequence of the coupled dynamics based on the next feedback loop in the sensory-motor system.

  3. Effect of Alternate Supply of Shielding Gases of Tungsten Inert Gas Welding on Mechanical Properties of Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Shinde, Neelam Vilas; Telsang, Martand Tamanacharya

    2016-07-01

    In the present study, an attempt is made to study the effect of alternate supply of the shielding gas in comparison with the conventional method of TIG welding with pure argon gas. The two sets of combination are used as 10-10 and 40-20 s for alternate supply of the Argon and Helium shielding gas respectively. The effect of alternate supply of shielding gas is studied on the mechanical properties like bend test, tensile test and impact test. The full factorial experimental design is applied for three set of combinations. The ANOVA is used to find significant parameters for the process and regression analysis used to develop the mathematical model. The result shows that the alternate supply of the shielding gas for 10-10 s provides better result for the bend, tensile and impact test as compared with the conventional argon gas and the alternate supply of 40-20 s argon and helium gas respectively. Welding speed can be increased for alternate supply of the shielding gas that can reduce the total welding cost.

  4. Confidence versus Performance as an Indicator of the Presence of Alternative Conceptions and Inadequate Problem-Solving Skills in Mechanics

    NASA Astrophysics Data System (ADS)

    Potgieter, Marietjie; Malatje, Esther; Gaigher, Estelle; Venter, Elsie

    2010-07-01

    This study investigated the use of performance-confidence relationships to signal the presence of alternative conceptions and inadequate problem-solving skills in mechanics. A group of 33 students entering physics at a South African university participated in the project. The test instrument consisted of 20 items derived from existing standardised tests from literature, each of which was followed by a self-reported measure of confidence of students in the correctness of their answers. Data collected for this study included students' responses to multiple-choice questions and open-ended explanations for their chosen answers. Fixed response physics and confidence data were logarithmically transformed according to the Rasch model to linear measures of performance and confidence. The free response explanations were carefully analysed for accuracy of conceptual understanding. Comparison of these results with raw score data and transformed measures of performance and confidence allowed a re-evaluation of the model developed by Hasan, Bagayoko, and Kelley in 1999 for the detection of alternative conceptions in mechanics. Application of this model to raw score data leads to inaccurate conclusions. However, application of the Hasan hypothesis to transformed measures of performance and confidence resulted in the accurate identification of items plagued by alternative conceptions. This approach also holds promise for the differentiation between over-confidence due to alternative conceptions or due to inadequate problem-solving skills. It could become a valuable tool for instructional design in mechanics.

  5. Instrumentation to study myofibril mechanics from static to artificial simulations of cardiac cycle.

    PubMed

    Vikhorev, Petr G; Ferenczi, Michael A; Marston, Steven B

    2016-01-01

    Many causes of heart muscle diseases and skeletal muscle diseases are inherited and caused by mutations in genes of sarcomere proteins which play either a structural or contractile role in the muscle cell. Tissue samples from human hearts with mutations can be obtained but often samples are only a few milligrams and it is necessary to freeze them for storage and transportation. Myofibrils are the fundamental contractile components of the muscle cell and retain all structural elements and contractile proteins performing in contractile event; moreover viable myofibrils can be obtained from frozen tissue.•We are describing a versatile technique for measuring the contractility and its Ca(2+) regulation in single myofibrils. The control of myofibril length, incubation medium and data acquisition is carried out using a digital acquisition board via computer software. Using computer control it is possible not only to measure contractile and mechanical parameters but also simulate complex protocols such as a cardiac cycle to vary length and medium independently.•This single myofibril force assay is well suited for physiological measurements. The system can be adapted to measure tension amplitude, rates of contraction and relaxation, Ca(2+) dependence of these parameters in dose-response measurements, length-dependent activation, stretch response, myofibril elasticity and response to simulated cardiac cycle length changes. Our approach provides an all-round quantitative way to measure myofibrils performance and to observe the effect of mutations or posttranslational modifications. The technique has been demonstrated by the study of contraction in heart with hypertrophic or dilated cardiomyopathy mutations in sarcomere proteins. PMID:27047763

  6. Instrumentation to study myofibril mechanics from static to artificial simulations of cardiac cycle.

    PubMed

    Vikhorev, Petr G; Ferenczi, Michael A; Marston, Steven B

    2016-01-01

    Many causes of heart muscle diseases and skeletal muscle diseases are inherited and caused by mutations in genes of sarcomere proteins which play either a structural or contractile role in the muscle cell. Tissue samples from human hearts with mutations can be obtained but often samples are only a few milligrams and it is necessary to freeze them for storage and transportation. Myofibrils are the fundamental contractile components of the muscle cell and retain all structural elements and contractile proteins performing in contractile event; moreover viable myofibrils can be obtained from frozen tissue.•We are describing a versatile technique for measuring the contractility and its Ca(2+) regulation in single myofibrils. The control of myofibril length, incubation medium and data acquisition is carried out using a digital acquisition board via computer software. Using computer control it is possible not only to measure contractile and mechanical parameters but also simulate complex protocols such as a cardiac cycle to vary length and medium independently.•This single myofibril force assay is well suited for physiological measurements. The system can be adapted to measure tension amplitude, rates of contraction and relaxation, Ca(2+) dependence of these parameters in dose-response measurements, length-dependent activation, stretch response, myofibril elasticity and response to simulated cardiac cycle length changes. Our approach provides an all-round quantitative way to measure myofibrils performance and to observe the effect of mutations or posttranslational modifications. The technique has been demonstrated by the study of contraction in heart with hypertrophic or dilated cardiomyopathy mutations in sarcomere proteins.

  7. Cell Cycle-Dependent Mechanisms Underlie Vincristine-Induced Death of Primary Acute Lymphoblastic Leukemia Cells.

    PubMed

    Kothari, Anisha; Hittelman, Walter N; Chambers, Timothy C

    2016-06-15

    Microtubule-targeting agents (MTA), such as the taxanes and vinca alkaloids, are used to treat a variety of cancers due to their ability to perturb microtubule dynamics. In cell culture, MTAs exert their anticancer effects primarily by causing mitotic arrest and cell death. However, accumulating indirect evidence suggests that MTAs may exert their cytotoxicity in human tumors by interfering with interphase microtubules. In this study, we sought to develop and characterize an experimental system in which to test the hypothesis that MTAs induce cell death during interphase. Primary adult acute lymphoblastic leukemia (ALL) cells treated with vincristine only weakly exhibited colocalization between mitotic and apoptotic markers and major characteristics of mitotic death, such as an increase in cells with 4N DNA content before the appearance of cells with <2N DNA content, suggesting a mixed response. Therefore, we separated ALL cells into distinct phases of the cell cycle by centrifugal elutriation, labeled cells with 5-ethynyl-2'-deoxyuridine (EdU), and then treated each population with vincristine. Cells isolated during G1 underwent cell death without evidence of EdU uptake, indicating that the cytotoxic effects of vincristine took place during G1 Conversely, cells isolated during S or G2-M phases underwent death following mitotic arrest. Thus, vincristine induces distinct death programs in primary ALL cells depending on cell-cycle phase, and cells in G1 are particularly susceptible to perturbation of interphase microtubules. Primary ALL cells may therefore provide a powerful model system in which to study the multimodal mechanisms underlying MTA-induced cell death. Cancer Res; 76(12); 3553-61. ©2016 AACR. PMID:27197148

  8. Experimental opto-mechanics with levitated nanoparticles: towards quantum control and thermodynamic cycles (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Kiesel, Nikolai; Blaser, Florian; Delic, Uros; Grass, David; Dechant, Andreas; Lutz, Eric; Bathaee, Marzieh; Aspelmeyer, Markus

    2015-08-01

    Combining optical levitation and cavity optomechanics constitutes a promising approach to prepare and control the motional quantum state of massive objects (>10^9 amu). This, in turn, would represent a completely new type of light-matter interface and has, for example, been predicted to enable experimental tests of macrorealistic models or of non-Newtonian gravity at small length scales. Such ideas have triggered significant experimental efforts to realizing such novel systems. To this end, we have recently successfully demonstrated cavity-cooling of a levitated sub-micron silica particle in a classical regime at a pressure of approximately 1mbar. Access to higher vacuum of approx. 10^-6 mbar has been demonstrated using 3D-feedback cooling in optical tweezers without cavity-coupling. Here we will illustrate our strategy towards trapping, 3D-cooling and quantum control of nanoparticles in ultra-high vacuum using cavity-based feedback cooling methods and clean particle loading with hollow-core photonic crystal fibers. We will also discuss the current experimental progress both in 3D-cavity cooling and HCPCF-based transport of nanoparticles. As yet another application of cavity-controlled levitated nanoparticles we will show how to implement a thermodynamic Sterling cycle operating in the underdamped regime. We present optimized protocols with respect to efficiency at maximum power in this little explored regime. We also show that the excellent level of control in our system will allow reproducing all relevant features of such optimized protocols. In a next step, this will enable studies of thermodynamics cycles in a regime where the quantization of the mechanical motion becomes relevant.

  9. Instrumentation to study myofibril mechanics from static to artificial simulations of cardiac cycle

    PubMed Central

    Vikhorev, Petr G.; Ferenczi, Michael A.; Marston, Steven B.

    2016-01-01

    Many causes of heart muscle diseases and skeletal muscle diseases are inherited and caused by mutations in genes of sarcomere proteins which play either a structural or contractile role in the muscle cell. Tissue samples from human hearts with mutations can be obtained but often samples are only a few milligrams and it is necessary to freeze them for storage and transportation. Myofibrils are the fundamental contractile components of the muscle cell and retain all structural elements and contractile proteins performing in contractile event; moreover viable myofibrils can be obtained from frozen tissue.•We are describing a versatile technique for measuring the contractility and its Ca2+ regulation in single myofibrils. The control of myofibril length, incubation medium and data acquisition is carried out using a digital acquisition board via computer software. Using computer control it is possible not only to measure contractile and mechanical parameters but also simulate complex protocols such as a cardiac cycle to vary length and medium independently.•This single myofibril force assay is well suited for physiological measurements. The system can be adapted to measure tension amplitude, rates of contraction and relaxation, Ca2+ dependence of these parameters in dose-response measurements, length-dependent activation, stretch response, myofibril elasticity and response to simulated cardiac cycle length changes. Our approach provides an all-round quantitative way to measure myofibrils performance and to observe the effect of mutations or posttranslational modifications. The technique has been demonstrated by the study of contraction in heart with hypertrophic or dilated cardiomyopathy mutations in sarcomere proteins. PMID:27047763

  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.

  11. Cell Cycle-Dependent Mechanisms Underlie Vincristine-Induced Death of Primary Acute Lymphoblastic Leukemia Cells.

    PubMed

    Kothari, Anisha; Hittelman, Walter N; Chambers, Timothy C

    2016-06-15

    Microtubule-targeting agents (MTA), such as the taxanes and vinca alkaloids, are used to treat a variety of cancers due to their ability to perturb microtubule dynamics. In cell culture, MTAs exert their anticancer effects primarily by causing mitotic arrest and cell death. However, accumulating indirect evidence suggests that MTAs may exert their cytotoxicity in human tumors by interfering with interphase microtubules. In this study, we sought to develop and characterize an experimental system in which to test the hypothesis that MTAs induce cell death during interphase. Primary adult acute lymphoblastic leukemia (ALL) cells treated with vincristine only weakly exhibited colocalization between mitotic and apoptotic markers and major characteristics of mitotic death, such as an increase in cells with 4N DNA content before the appearance of cells with <2N DNA content, suggesting a mixed response. Therefore, we separated ALL cells into distinct phases of the cell cycle by centrifugal elutriation, labeled cells with 5-ethynyl-2'-deoxyuridine (EdU), and then treated each population with vincristine. Cells isolated during G1 underwent cell death without evidence of EdU uptake, indicating that the cytotoxic effects of vincristine took place during G1 Conversely, cells isolated during S or G2-M phases underwent death following mitotic arrest. Thus, vincristine induces distinct death programs in primary ALL cells depending on cell-cycle phase, and cells in G1 are particularly susceptible to perturbation of interphase microtubules. Primary ALL cells may therefore provide a powerful model system in which to study the multimodal mechanisms underlying MTA-induced cell death. Cancer Res; 76(12); 3553-61. ©2016 AACR.

  12. A Modified Wilson Cycle Scenario Based on Thermo-Mechanical Model

    NASA Astrophysics Data System (ADS)

    Baes, M.; Sobolev, S. V.

    2014-12-01

    The major problem of classical Wilson Cycle concept is the suggested conversion of the passive continental margin to the active subduction zone. Previous modeling studies assumed either unusually thick felsic continental crust at the margin (over 40 km) or unusually low lithospheric thickness (less than 70 km) to simulate this process. Here we propose a new triggering factor in subduction initiation process that is mantle suction force. Based on this proposal we suggest a modification of Wilson Cycle concept. Sometime after opening and extension of oceanic basin, continental passive margin moves over the slab remnants of the former active subduction zones in deep mantle. Such slab remnants or deep slabs of neighboring active subduction zones produce a suction mantle flow introducing additional compression at the passive margin. It results in the initiation of a new subduction zone, hence starting the closing phase of Wilson Cycle. In this scenario the weakness of continental crust near the passive margin which is inherited from the rifting phase and horizontal push force induced from far-field topographic gradient within the continent facilitate and speed up subduction initiation process. Our thermo-mechanical modeling shows that after a few tens of million years a shear zone may indeed develop along the passive margin that has typical two-layered 35 km thick continental crust and thermal lithosphere thicker than 100 km if there is a broad mantle down-welling flow below the margin. Soon after formation of this shear zone oceanic plate descends into mantle and subduction initiates. Subduction initiation occurs following over-thrusting of continental crust and retreating of future trench. In models without far-field topographic gradient within the continent subduction initiation requires weaker passive margin. Our results also indicate that subduction initiation depends on several parameters such as magnitude, domain size and location of suction mantle flow

  13. Use of Guided Acoustic Waves to Assess the Effects of Thermal-Mechanical Cycling on Composite Stiffness

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Madaras, Eric I.

    2000-01-01

    The introduction of new, advanced composite materials into aviation systems requires it thorough understanding of the long-term effects of combined thermal and mechanical loading. As part of a study to evaluate the effects of thermal-mechanical cycling, it guided acoustic (Lamb) wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the velocity dispersion curve. A series of 16 and 32-ply composite laminates were subjected to it thermal-mechanical loading profile in load frames equipped with special environmental chambers. The composite systems studied were it graphite fiber reinforced amorphous thermoplastic polyimide and it graphite fiber reinforced bismaleimide thermoset. The samples were exposed to both high and low temperature extremes its well as high and low strain profiles. The bending and out-of-plane stiffnesses for composite sample that have undergone over 6,000 cycles of thermal-mechanical loading are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 20% at 4,936 loading cycles for the graphite/thermoplastic samples and up to 64% at 4,706 loading cycles for the graphite/thermoset samples.

  14. Computational study on the behaviors of granular materials under mechanical cycling

    SciTech Connect

    Wang, Xiaoliang; Ye, Minyou; Chen, Hongli

    2015-11-07

    Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal force distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis.

  15. Computational study on the behaviors of granular materials under mechanical cycling

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoliang; Ye, Minyou; Chen, Hongli

    2015-11-01

    Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal force distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis.

  16. Fiber-reinforced composite analysis using optical coherence tomography after mechanical and thermal cycling

    NASA Astrophysics Data System (ADS)

    Kyotoku, B. B. C.; Braz, A. K. S.; Braz, R.; Gomes, A. S. L.

    2007-02-01

    Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 μm resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

  17. Methyl Jasmonate: Putative Mechanisms of Action on Cancer Cells Cycle, Metabolism, and Apoptosis

    PubMed Central

    Cesari, Italo Mario; Figueiredo Rodrigues, Mariana; Mendonça, Bruna dos Santos; Amôedo, Nivea Dias; Rumjanek, Franklin David

    2014-01-01

    Methyl jasmonate (MJ), an oxylipid that induces defense-related mechanisms in plants, has been shown to be active against cancer cells both in vitro and in vivo, without affecting normal cells. Here we review most of the described MJ activities in an attempt to get an integrated view and better understanding of its multifaceted modes of action. MJ (1) arrests cell cycle, inhibiting cell growth and proliferation, (2) causes cell death through the intrinsic/extrinsic proapoptotic, p53-independent apoptotic, and nonapoptotic (necrosis) pathways, (3) detaches hexokinase from the voltage-dependent anion channel, dissociating glycolytic and mitochondrial functions, decreasing the mitochondrial membrane potential, favoring cytochrome c release and ATP depletion, activating pro-apoptotic, and inactivating antiapoptotic proteins, (4) induces reactive oxygen species mediated responses, (5) stimulates MAPK-stress signaling and redifferentiation in leukemia cells, (6) inhibits overexpressed proinflammatory enzymes in cancer cells such as aldo-keto reductase 1 and 5-lipoxygenase, and (7) inhibits cell migration and shows antiangiogenic and antimetastatic activities. Finally, MJ may act as a chemosensitizer to some chemotherapics helping to overcome drug resistant. The complete lack of toxicity to normal cells and the rapidity by which MJ causes damage to cancer cells turn MJ into a promising anticancer agent that can be used alone or in combination with other agents. PMID:24648844

  18. Mechanical Unloading of Mouse Bone in Microgravity Significantly Alters Cell Cycle Gene Set Expression

    NASA Astrophysics Data System (ADS)

    Blaber, Elizabeth; Dvorochkin, Natalya; Almeida, Eduardo; Kaplan, Warren; Burns, Brnedan

    2012-07-01

    Spaceflight factors, including microgravity and space radiation, have many detrimental short-term effects on human physiology, including muscle and bone degradation, and immune system dysfunction. The long-term progression of these physiological effects is still poorly understood, and a serious concern for long duration spaceflight missions. We hypothesized that some of the degenerative effects of spaceflight may be caused in part by an inability of stem cells to proliferate and differentiate normally resulting in an impairment of tissue regenerative processes. Furthermore, we hypothesized that long-term bone tissue degeneration in space may be mediated by activation of the p53 signaling network resulting in cell cycle arrest and/or apoptosis in osteoprogenitors. In our analyses we found that spaceflight caused significant bone loss in the weight-bearing bones of mice with a 6.3% reduction in bone volume and 11.9% decrease in bone thickness associated with increased osteoclastic activity. Along with this rapid bone loss we also observed alterations in the cell cycle characterized by an increase in the Cdkn1a/p21 cell cycle arrest molecule independent of Trp53. Overexpression of Cdkn1a/p21 was localized to osteoblasts lining the periosteal surface of the femur and chondrocytes in the head of the femur, suggesting an inhibition of proliferation in two key regenerative cell types of the femur in response to spaceflight. Additionally we found overexpression of several matrix degradation molecules including MMP-1a, 3 and 10, of which MMP-10 was localized to osteocytes within the shaft of the femur. This, in conjunction with 40 nm resolution synchrotron nano-Computed Tomography (nano-CT) observations of an increase in osteocyte lacunae cross-sectional area, perimeter and a decrease in circularity indicates a potential role for osteocytic osteolysis in the observed bone degeneration in spaceflight. To further investigate the genetic response of bone to mechanical

  19. A physical mechanism for the prediction of the sunspot number during solar cycle 21. [graphs (charts)

    NASA Technical Reports Server (NTRS)

    Schatten, K. H.; Scherrer, P. H.; Svalgaard, L.; Wilcox, J. M.

    1978-01-01

    On physical grounds it is suggested that the sun's polar field strength near a solar minimum is closely related to the following cycle's solar activity. Four methods of estimating the sun's polar magnetic field strength near solar minimum are employed to provide an estimate of cycle 21's yearly mean sunspot number at solar maximum of 140 plus or minus 20. This estimate is considered to be a first order attempt to predict the cycle's activity using one parameter of physical importance.

  20. Regime shifts in exploited marine food webs: detecting mechanisms underlying alternative stable states using size-structured community dynamics theory

    PubMed Central

    Gårdmark, Anna; Casini, Michele; Huss, Magnus; van Leeuwen, Anieke; Hjelm, Joakim; Persson, Lennart; de Roos, André M.

    2015-01-01

    Many marine ecosystems have undergone ‘regime shifts’, i.e. abrupt reorganizations across trophic levels. Establishing whether these constitute shifts between alternative stable states is of key importance for the prospects of ecosystem recovery and for management. We show how mechanisms underlying alternative stable states caused by predator–prey interactions can be revealed in field data, using analyses guided by theory on size-structured community dynamics. This is done by combining data on individual performance (such as growth and fecundity) with information on population size and prey availability. We use Atlantic cod (Gadus morhua) and their prey in the Baltic Sea as an example to discuss and distinguish two types of mechanisms, ‘cultivation-depensation’ and ‘overcompensation’, that can cause alternative stable states preventing the recovery of overexploited piscivorous fish populations. Importantly, the type of mechanism can be inferred already from changes in the predators' body growth in different life stages. Our approach can thus be readily applied to monitored stocks of piscivorous fish species, for which this information often can be assembled. Using this tool can help resolve the causes of catastrophic collapses in marine predatory–prey systems and guide fisheries managers on how to successfully restore collapsed piscivorous fish stocks.

  1. High temperature low cycle fatigue mechanisms for nickel base and a copper base alloy. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Shih, C. I.

    1982-01-01

    Damage mechanisms were studied in Rene' 95 and NARloy Z, using optical, scanning and transmission in microscopy. In necklace Rene' 95, crack initiation was mainly associated with cracking of surface MC carbides, except for hold time tests at higher strain ranges where initiation was associated more with a grain boundary mechanism. A mixed mode of propagation with a faceted fracture morphology was typical for all cycle characters. The dependence of life on maximum tensile stress can be demonstrated by the data falling onto three lines corresponding to the three tensile hold times, in the life against maximum tensile stress plot. In NARloy Z, crack initiation was always at the grain boundaries. The mode of crack propagation depended on the cycle character. The life decreased with decreasing strain rate and with tensile holds. In terms of damage mode, different life prediction laws may be applicable to different cycle characters.

  2. A post-transcriptional mechanism contributes to circadian cycling of a per-beta-galactosidase fusion protein.

    PubMed Central

    Zwiebel, L J; Hardin, P E; Liu, X; Hall, J C; Rosbash, M

    1991-01-01

    The period gene (per) of Drosophila melanogaster affects circadian rhythms. Circadian fluctuations in per mRNA levels are thought to contribute to circadian fluctuations in per protein levels in the heads of adult flies. To address the mechanisms underlying these oscillatory phenomena, we have analyzed RNA and protein cycling from two per-beta-galactosidase fusion genes. These studies demonstrate that 5' noncoding sequences from per are sufficient to cause the fusion mRNA levels to cycle in a wild-type (rhythmic) background. Protein cycling requires additional sequences derived from the per coding region. The data suggest that there is a per-dependent posttranscriptional mechanism that is under circadian clock control required for per protein levels to fluctuate in a rhythmic fashion. Images PMID:1902573

  3. [Mechanical infertility in the female population of the Kielce province. III. Evaluation of sexual steroid levels during the menstrual cycle].

    PubMed

    Szczurowicz, A; Witczak, A; Swiercz, G; Szczurowicz, A; Ziółkowski, T

    1993-10-01

    The results of the sexual steroids RIA examinations during the menstrual cycle at women with mechanical sterility in confrontation with the group of fertile women were shown. Mean concentrations of progesterone and estradiol in serum were statistically significant in sterile women. In the group of women with mechanical sterility there was no estrogen peak and levels of estradiol in ovulation period were significantly lower in confrontation with the control group.

  4. Energy and emission benefits of alternative transportation liquid fuels derived from switchgrass: a fuel life cycle assessment.

    PubMed

    Wu, May; Wu, Ye; Wang, Michael

    2006-01-01

    We conducted a mobility chains, or well-to-wheels (WTW), analysis to assess the energy and emission benefits of cellulosic biomass for the U.S. transportation sector in the years 2015-2030. We estimated the life-cycle energy consumption and emissions associated with biofuel production and use in light-duty vehicle (LDV) technologies by using the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model. Analysis of biofuel production was based on ASPEN Plus model simulation of an advanced fermentation process to produce fuel ethanol/protein, a thermochemical process to produce Fischer-Tropsch diesel (FTD) and dimethyl ether (DME), and a combined heat and power plant to co-produce steam and electricity. Our study revealed that cellulosic biofuels as E85 (mixture of 85% ethanol and 15% gasoline by volume), FTD, and DME offer substantial savings in petroleum (66-93%) and fossil energy (65-88%) consumption on a per-mile basis. Decreased fossil fuel use translates to 82-87% reductions in greenhouse gas emissions across all unblended cellulosic biofuels. In urban areas, our study shows net reductions for almost all criteria pollutants, with the exception of carbon monoxide (unchanged), for each of the biofuel production option examined. Conventional and hybrid electric vehicles, when fueled with E85, could reduce total sulfur oxide (SO(x)) emissions to 39-43% of those generated by vehicles fueled with gasoline. By using bio-FTD and bio-DME in place of diesel, SO(x) emissions are reduced to 46-58% of those generated by diesel-fueled vehicles. Six different fuel production options were compared. This study strongly suggests that integrated heat and power co-generation by means of gas turbine combined cycle is a crucial factor in the energy savings and emission reductions.

  5. Energy and emission benefits of alternative transportation liquid fuels derived from switchgrass: a fuel life cycle assessment.

    PubMed

    Wu, May; Wu, Ye; Wang, Michael

    2006-01-01

    We conducted a mobility chains, or well-to-wheels (WTW), analysis to assess the energy and emission benefits of cellulosic biomass for the U.S. transportation sector in the years 2015-2030. We estimated the life-cycle energy consumption and emissions associated with biofuel production and use in light-duty vehicle (LDV) technologies by using the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model. Analysis of biofuel production was based on ASPEN Plus model simulation of an advanced fermentation process to produce fuel ethanol/protein, a thermochemical process to produce Fischer-Tropsch diesel (FTD) and dimethyl ether (DME), and a combined heat and power plant to co-produce steam and electricity. Our study revealed that cellulosic biofuels as E85 (mixture of 85% ethanol and 15% gasoline by volume), FTD, and DME offer substantial savings in petroleum (66-93%) and fossil energy (65-88%) consumption on a per-mile basis. Decreased fossil fuel use translates to 82-87% reductions in greenhouse gas emissions across all unblended cellulosic biofuels. In urban areas, our study shows net reductions for almost all criteria pollutants, with the exception of carbon monoxide (unchanged), for each of the biofuel production option examined. Conventional and hybrid electric vehicles, when fueled with E85, could reduce total sulfur oxide (SO(x)) emissions to 39-43% of those generated by vehicles fueled with gasoline. By using bio-FTD and bio-DME in place of diesel, SO(x) emissions are reduced to 46-58% of those generated by diesel-fueled vehicles. Six different fuel production options were compared. This study strongly suggests that integrated heat and power co-generation by means of gas turbine combined cycle is a crucial factor in the energy savings and emission reductions. PMID:16889378

  6. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: A Method to Design Synthetic Cell-Cycle Networks

    NASA Astrophysics Data System (ADS)

    Miao, Ke-Ke

    2009-07-01

    The interactions among proteins, DNA and RNA in an organism form elaborate cell-cycle networks which govern cell growth and proliferation. Understanding the common structure of cell-cycle networks will be of great benefit to science research. Here, inspired by the importance of the cell-cycle regulatory network of yeast which has been studied intensively, we focus on small networks with 11 nodes, equivalent to that of the cell-cycle regulatory network used by Li et al. [Proc. Natl. Acad. Sci. USA 101(2004)4781] Using a Boolean model, we study the correlation between structure and function, and a possible common structure. It is found that cascade-like networks with a great number of interactions between nodes are stable. Based on these findings, we are able to construct synthetic networks that have the same functions as the cell-cycle regulatory network.

  7. Life cycle assessment of integrated waste management systems for alternative legacy scenarios of the London Olympic Park.

    PubMed

    Parkes, Olga; Lettieri, Paola; Bogle, I David L

    2015-06-01

    This paper presents the results of the life cycle assessment (LCA) of 10 integrated waste management systems (IWMSs) for 3 potential post-event site design scenarios of the London Olympic Park. The aim of the LCA study is to evaluate direct and indirect emissions resulting from various treatment options of municipal solid waste (MSW) annually generated on site together with avoided emissions resulting from energy, materials and nutrients recovery. IWMSs are modelled using GaBi v6.0 Product Sustainability software and results are presented based on the CML (v.Nov-10) characterisation method. The results show that IWMSs with advanced thermal treatment (ATT) and incineration with energy recovery have the lowest Global Warming Potential (GWP) than IWMSs where landfill is the primary waste treatment process. This is due to higher direct emissions and lower avoided emissions from the landfill process compared to the emissions from the thermal treatment processes. LCA results demonstrate that significant environmental savings are achieved through substitution of virgin materials with recycled ones. The results of the sensitivity analysis carried out for IWMS 1 shows that increasing recycling rate by 5%, 10% and 15% compared to the baseline scenario can reduce GWP by 8%, 17% and 25% respectively. Sensitivity analysis also shows how changes in waste composition affect the overall result of the system. The outcomes of such assessments provide decision-makers with fundamental information regarding the environmental impacts of different waste treatment options necessary for sustainable waste management planning. PMID:25837786

  8. Comment on "Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle".

    PubMed

    González-Díaz, L A; Díaz-Solórzano, S

    2015-05-01

    In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this statement is incorrect. In particular, we prove that the state at the beginning of the cycle is mixed due to the process of measuring energy. PMID:26066282

  9. Comment on "Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle".

    PubMed

    González-Díaz, L A; Díaz-Solórzano, S

    2015-05-01

    In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this statement is incorrect. In particular, we prove that the state at the beginning of the cycle is mixed due to the process of measuring energy.

  10. Life cycle assessment of integrated waste management systems for alternative legacy scenarios of the London Olympic Park

    SciTech Connect

    Parkes, Olga Lettieri, Paola Bogle, I. David L.

    2015-06-15

    Highlights: • Application of LCA in planning integrated waste management systems. • Environmental valuation of 3 legacy scenarios for the Olympic Park. • Hot-spot analysis highlights the importance of energy and materials recovery. • Most environmental savings are achieved through materials recycling. • Sensitivity analysis shows importance of waste composition and recycling rates. - Abstract: This paper presents the results of the life cycle assessment (LCA) of 10 integrated waste management systems (IWMSs) for 3 potential post-event site design scenarios of the London Olympic Park. The aim of the LCA study is to evaluate direct and indirect emissions resulting from various treatment options of municipal solid waste (MSW) annually generated on site together with avoided emissions resulting from energy, materials and nutrients recovery. IWMSs are modelled using GaBi v6.0 Product Sustainability software and results are presented based on the CML (v.Nov-10) characterisation method. The results show that IWMSs with advanced thermal treatment (ATT) and incineration with energy recovery have the lowest Global Warming Potential (GWP) than IWMSs where landfill is the primary waste treatment process. This is due to higher direct emissions and lower avoided emissions from the landfill process compared to the emissions from the thermal treatment processes. LCA results demonstrate that significant environmental savings are achieved through substitution of virgin materials with recycled ones. The results of the sensitivity analysis carried out for IWMS 1 shows that increasing recycling rate by 5%, 10% and 15% compared to the baseline scenario can reduce GWP by 8%, 17% and 25% respectively. Sensitivity analysis also shows how changes in waste composition affect the overall result of the system. The outcomes of such assessments provide decision-makers with fundamental information regarding the environmental impacts of different waste treatment options necessary for

  11. Alternative ways of using field-based estimates to calibrate ecosystem models and their implications for carbon cycle studies

    USGS Publications Warehouse

    He, Yujie; Zhuang, Qianlai; McGuire, David; Liu, Yaling; Chen, Min

    2013-01-01

    Model-data fusion is a process in which field observations are used to constrain model parameters. How observations are used to constrain parameters has a direct impact on the carbon cycle dynamics simulated by ecosystem models. In this study, we present an evaluation of several options for the use of observations in modeling regional carbon dynamics and explore the implications of those options. We calibrated the Terrestrial Ecosystem Model on a hierarchy of three vegetation classification levels for the Alaskan boreal forest: species level, plant-functional-type level (PFT level), and biome level, and we examined the differences in simulated carbon dynamics. Species-specific field-based estimates were directly used to parameterize the model for species-level simulations, while weighted averages based on species percent cover were used to generate estimates for PFT- and biome-level model parameterization. We found that calibrated key ecosystem process parameters differed substantially among species and overlapped for species that are categorized into different PFTs. Our analysis of parameter sets suggests that the PFT-level parameterizations primarily reflected the dominant species and that functional information of some species were lost from the PFT-level parameterizations. The biome-level parameterization was primarily representative of the needleleaf PFT and lost information on broadleaf species or PFT function. Our results indicate that PFT-level simulations may be potentially representative of the performance of species-level simulations while biome-level simulations may result in biased estimates. Improved theoretical and empirical justifications for grouping species into PFTs or biomes are needed to adequately represent the dynamics of ecosystem functioning and structure.

  12. Ignition assist systems for direct-injected, diesel cycle, medium-duty alternative fuel engines: Final report phase 1

    SciTech Connect

    Chan, A.K.

    2000-02-23

    This report is a summary of the results of Phase 1 of this contract. The objective was to evaluate the potential of assist technologies for direct-injected alternative fuel engines vs. glow plug ignition assist. The goal was to demonstrate the feasibility of an ignition system life of 10,000 hours and a system cost of less than 50% of the glow plug system, while meeting or exceeding the engine thermal efficiency obtained with the glow plug system. There were three tasks in Phase 1. Under Task 1, a comprehensive review of feasible ignition options for DING engines was completed. The most promising options are: (1) AC and the ''SmartFire'' spark, which are both long-duration, low-power (LDLP) spark systems; (2) the short-duration, high-power (SDHP) spark system; (3) the micropilot injection ignition; and (4) the stratified charge plasma ignition. Efforts concentrated on investigating the AC spark, SmartFire spark, and short-duration/high-power spark systems. Using proprietary pricing information, the authors predicted that the commercial costs for the AC spark, the short-duration/high-power spark and SmartFire spark systems will be comparable (if not less) to the glow plug system. Task 2 involved designing and performing bench tests to determine the criteria for the ignition system and the prototype spark plug for Task 3. The two most important design criteria are the high voltage output requirement of the ignition system and the minimum electrical insulation requirement for the spark plug. Under Task 3, all the necessary hardware for the one-cylinder engine test was designed. The hardware includes modified 3126 cylinder heads, specially designed prototype spark plugs, ignition system electronics, and parts for the system installation. Two 3126 cylinder heads and the SmartFire ignition system were procured, and testing will begin in Phase 2 of this subcontract.

  13. Alternative Activation Mechanisms of Protein Kinase B Trigger Distinct Downstream Signaling Responses*

    PubMed Central

    Balzano, Deborah; Fawal, Mohamad-Ali; Velázquez, Jose V.; Santiveri, Clara M.; Yang, Joshua; Pastor, Joaquín; Campos-Olivas, Ramón; Djouder, Nabil; Lietha, Daniel

    2015-01-01

    Protein kinase B (PKB/Akt) is an important mediator of signals that control various cellular processes including cell survival, growth, proliferation, and metabolism. PKB promotes these processes by phosphorylating many cellular targets, which trigger distinct downstream signaling events. However, how PKB is able to selectively target its substrates to induce specific cellular functions remains elusive. Here we perform a systematic study to dissect mechanisms that regulate intrinsic kinase activity versus mechanisms that specifically regulate activity toward specific substrates. We demonstrate that activation loop phosphorylation and the C-terminal hydrophobic motif are essential for high PKB activity in general. On the other hand, we identify membrane targeting, which for decades has been regarded as an essential step in PKB activation, as a mechanism mainly affecting substrate selectivity. Further, we show that PKB activity in cells can be triggered independently of PI3K by initial hydrophobic motif phosphorylation, presumably through a mechanism analogous to other AGC kinases. Importantly, different modes of PKB activation result in phosphorylation of distinct downstream targets. Our data indicate that specific mechanisms have evolved for signaling nodes, like PKB, to select between various downstream events. Targeting such mechanisms selectively could facilitate the development of therapeutics that might limit toxic side effects. PMID:26286748

  14. Molecular identification of larvae of a tetraphyllidean tapeworm (Platyhelminthes: Eucestoda) in a razor clam as an alternative intermediate host in the life cycle of Acanthobothrium brevissime.

    PubMed

    Holland, Nicholas D; Wilson, Nerida G

    2009-10-01

    Dwarf razor clams (Ensis minor) in the Gulf of Mexico are known to be infected with plerocercoid larvae of a tetraphyllidean tapeworm. Here, we show that these larvae live unencysted in the intestinal lumen of the clam. Morphologically, the larvae are similar to (although significantly larger than) tapeworm larvae previously described living in the gut of amphioxus (Branchiostoma floridae) from the same habitat. Sequence data from the D2 region of the 28S rDNA from clam-infecting larvae were identical to the sequence of Acanthobothrium brevissime isolated as larvae from amphioxus and as adults from a stingray (Dasyatis say). The sequence data leave little doubt that the dwarf razor clam and the amphioxus are alternative intermediate hosts in the life cycle of A. brevissime. PMID:19366282

  15. Mechanical and piezoelectric properties of zinc oxide nanorods grown on conductive textile fabric as an alternative substrate

    NASA Astrophysics Data System (ADS)

    Khan, Azam; Hussain, Mushtaque; Nur, Omer; Willander, Magnus

    2014-08-01

    The present research is devoted to understanding the mechanism and causes of variation in the piezoelectric potential generated from vertically aligned zinc oxide (ZnO) nanorods (NRs), which were grown on a conductive textile fabric as an alternative substrate by using the aqueous chemical growth method. The piezoelectric voltage was harvested from vertically aligned ZnO NRs having different physical parameters by using atomic force microscopy in contact mode and the variation in the generated piezoelectricity was investigated. The generated output potential indicates that different physical parameters such aspect ratio, crystal size and lattice internal crystal strain have a strong influence on the piezoelectric properties of vertically aligned ZnO NRs, which were grown on a textile fabric. Presented results indicate that textiles can be used as an alternative substrate just like the other conventional substrates, because our results are similar/better than many reported works on conventional substrates.

  16. Development and validation of an alternative disturbed skin model by mechanical abrasion to study drug penetration

    PubMed Central

    Schlupp, P.; Weber, M.; Schmidts, T.; Geiger, K.; Runkel, F.

    2014-01-01

    Pharmaceuticals and cosmetics for dermal application are usually tested on healthy skin, although the primary permeation barrier, the stratum corneum, is often impaired by skin diseases or small skin lesions, especially on the hands. These skin conditions can considerably influence the permeation of chemicals and drugs. Furthermore, risk assessment for example of nanoparticles should be performed under various skin conditions to reflect the true circumstances. Therefore, an alternative and reproducible method for a high throughput of skin samples with impaired skin barrier was developed and verified by skin permeation studies (25 h) of caffeine, sorbic acid and testosterone compared to healthy (untreated) and tape-stripped skin. Skin barrier disruption was controlled by TEWL measurement. Skin permeation of the three substances was increased in tape-stripped and abraded skin compared to untreated skin due to the reduced barrier integrity. Enhancement of drug uptake was highest for the most hydrophilic substance, caffeine, followed by sorbic acid and lipophilic testosterone. No significant difference in drug uptake studies was observed between the new abrasion method with an aluminum-coated sponge and the tape-stripping method. The obtained results demonstrate that this abrasion method is an alternative way to achieve a disturbed skin barrier for drug and chemical uptake studies. PMID:25756004

  17. Life cycle assessment of water supply alternatives in water-receiving areas of the South-to-North Water Diversion Project in China.

    PubMed

    Li, Yi; Xiong, Wei; Zhang, Wenlong; Wang, Chao; Wang, Peifang

    2016-02-01

    To alleviate the water shortage in northern China, the Chinese government launched the world's largest water diversion project, the South-to-North Water Diversion Project (SNWDP), which delivers water from water-sufficient southern China to water-deficient northern China. However, an up-to-date study has not been conducted to determine whether the project is a favorable option to augment the water supply from an environmental perspective. The life cycle assessment (LCA) methodology integrated with a freshwater withdrawal category (FWI) was adopted to compare water supply alternatives in the water-receiving areas of the SNWDP, i.e., water diversion, wastewater reclamation and seawater desalination. Beijing, Tianjin, Jinan and Qingdao were studied as representative cities because they are the primary water-receiving areas of the SNWDP. The results revealed that the operation phase played the dominant role in all but one of the life cycle impact categories considered and contributed to more than 70% of their scores. For Beijing and Tianjin, receiving water through the SNWDP is the most sustainable option to augment the water supply. The result can be drawn in all of the water-receiving areas of the middle route of the SNWDP. For Jinan and Qingdao, the most sustainable option is the wastewater reclamation system. The seawater desalination system obtains the highest score of the standard impact indicators in all of the study areas, whereas it is the most favorable water supply option when considering the freshwater withdrawal impact. Although the most sustainable water supply alternative was recommended through an LCA analysis, multi-water resources should be integrated into the region's water supply from the perspective of water sustainability. The results of this study provide a useful recommendation on the management of water resources for China.

  18. Life cycle assessment of water supply alternatives in water-receiving areas of the South-to-North Water Diversion Project in China.

    PubMed

    Li, Yi; Xiong, Wei; Zhang, Wenlong; Wang, Chao; Wang, Peifang

    2016-02-01

    To alleviate the water shortage in northern China, the Chinese government launched the world's largest water diversion project, the South-to-North Water Diversion Project (SNWDP), which delivers water from water-sufficient southern China to water-deficient northern China. However, an up-to-date study has not been conducted to determine whether the project is a favorable option to augment the water supply from an environmental perspective. The life cycle assessment (LCA) methodology integrated with a freshwater withdrawal category (FWI) was adopted to compare water supply alternatives in the water-receiving areas of the SNWDP, i.e., water diversion, wastewater reclamation and seawater desalination. Beijing, Tianjin, Jinan and Qingdao were studied as representative cities because they are the primary water-receiving areas of the SNWDP. The results revealed that the operation phase played the dominant role in all but one of the life cycle impact categories considered and contributed to more than 70% of their scores. For Beijing and Tianjin, receiving water through the SNWDP is the most sustainable option to augment the water supply. The result can be drawn in all of the water-receiving areas of the middle route of the SNWDP. For Jinan and Qingdao, the most sustainable option is the wastewater reclamation system. The seawater desalination system obtains the highest score of the standard impact indicators in all of the study areas, whereas it is the most favorable water supply option when considering the freshwater withdrawal impact. Although the most sustainable water supply alternative was recommended through an LCA analysis, multi-water resources should be integrated into the region's water supply from the perspective of water sustainability. The results of this study provide a useful recommendation on the management of water resources for China. PMID:26619399

  19. Kinetic model of mitochondrial Krebs cycle: unraveling the mechanism of salicylate hepatotoxic effects.

    PubMed

    Mogilevskaya, Ekaterina; Demin, Oleg; Goryanin, Igor

    2006-10-01

    This paper studies the effect of salicylate on the energy metabolism of mitochondria using in silico simulations. A kinetic model of the mitochondrial Krebs cycle is constructed using information on the individual enzymes. Model parameters for the rate equations are estimated using in vitro experimental data from the literature. Enzyme concentrations are determined from data on respiration in mitochondrial suspensions containing glutamate and malate. It is shown that inhibition in succinate dehydrogenase and alpha-ketoglutarate dehydrogenase by salicylate contributes substantially to the cumulative inhibition of the Krebs cycle by salicylates. Uncoupling of oxidative phosphorylation has little effect and coenzyme A consumption in salicylates transformation processes has an insignificant effect on the rate of substrate oxidation in the Krebs cycle. It is found that the salicylate-inhibited Krebs cycle flux can be increased by flux redirection through addition of external glutamate and malate, and depletion in external alpha-ketoglutarate and glycine concentrations.

  20. Influence of duty cycle on the power-duration relationship: observations and potential mechanisms.

    PubMed

    Broxterman, R M; Ade, C J; Wilcox, S L; Schlup, S J; Craig, J C; Barstow, T J

    2014-02-01

    The highest sustainable rate of aerobic metabolism [critical power (CP)] and the finite amount of work that can be performed above CP (W' [curvature constant]) were determined under two muscle contraction duty cycles. Eight men completed at least three constant-power handgrip tests to exhaustion to determine CP and W' for 50% and 20% duty cycles, while brachial artery blood flow (Q̇BA) and deoxygenated-[hemoglobin + myoglobin] (deoxy-[Hb+Mb]) were measured. CP was lower for the 50% duty cycle (3.9 ± 0.9 W) than the 20% duty cycle (5.1 ± 0.8 W; p < 0.001), while W' was not significantly different (50% duty cycle: 452 ± 141 J vs. 20% duty cycle: 432 ± 130 J; p > 0.05). At the same power output, Q̇BA and deoxy-[Hb + Mb] achieved higher end-exercise values for the 20% duty cycle (9.87 ± 1.73 ml·s(-1); 51.7 ± 4.7 μM) than the 50% duty cycle (7.37 ± 1.76 ml·s(-1), p < 0.001; 44.3 ± 2.4 μM, p < 0.03). These findings indicate that blood flow influences CP, but not W'.

  1. Evaluation of new alternatives in wastewater treatment plants based on dynamic modelling and life cycle assessment (DM-LCA).

    PubMed

    Bisinella de Faria, A B; Spérandio, M; Ahmadi, A; Tiruta-Barna, L

    2015-11-01

    With a view to quantifying the energy and environmental advantages of Urine Source-Separation (USS) combined with different treatment processes, five wastewater treatment plant (WWTP) scenarios were compared to a reference scenario using Dynamic Modelling (DM) and Life Cycle Assessment (LCA), and an integrated DM-LCA framework was thus developed. Dynamic simulations were carried out in BioWin(®) in order to obtain a realistic evaluation of the dynamic behaviour and performance of plants under perturbation. LCA calculations were performed within Umberto(®) using the Ecoinvent database. A Python™ interface was used to integrate and convert simulation data and to introduce them into Umberto(®) to achieve a complete LCA evaluation comprising foreground and background processes. Comparisons between steady-state and dynamic simulations revealed the importance of considering dynamic aspects such as nutrient and flow peaks. The results of the evaluation highlighted the potential of the USS scenario for nutrient recovery whereas the Enhanced Primary Clarification (EPC) scenario gave increased biogas production and also notably decreased aeration consumption, leading to a positive energy balance. Both USS and EPC scenarios also showed increased stability of plant operation, with smaller daily averages of total nitrogen and phosphorus. In this context, USS and EPC results demonstrated that the coupled USS + EPC scenario and its combinations with agricultural spreading of N-rich effluent and nitritation/anaerobic deammonification could present an energy-positive balance with respectively 27% and 33% lower energy requirements and an increase in biogas production of 23%, compared to the reference scenario. The coupled scenarios also presented lesser environmental impacts (reduction of 31% and 39% in total endpoint impacts) along with effluent quality well within the specified limits. The marked environmental performance (reduction of global warming) when nitrogen is used

  2. Evaluation of new alternatives in wastewater treatment plants based on dynamic modelling and life cycle assessment (DM-LCA).

    PubMed

    Bisinella de Faria, A B; Spérandio, M; Ahmadi, A; Tiruta-Barna, L

    2015-11-01

    With a view to quantifying the energy and environmental advantages of Urine Source-Separation (USS) combined with different treatment processes, five wastewater treatment plant (WWTP) scenarios were compared to a reference scenario using Dynamic Modelling (DM) and Life Cycle Assessment (LCA), and an integrated DM-LCA framework was thus developed. Dynamic simulations were carried out in BioWin(®) in order to obtain a realistic evaluation of the dynamic behaviour and performance of plants under perturbation. LCA calculations were performed within Umberto(®) using the Ecoinvent database. A Python™ interface was used to integrate and convert simulation data and to introduce them into Umberto(®) to achieve a complete LCA evaluation comprising foreground and background processes. Comparisons between steady-state and dynamic simulations revealed the importance of considering dynamic aspects such as nutrient and flow peaks. The results of the evaluation highlighted the potential of the USS scenario for nutrient recovery whereas the Enhanced Primary Clarification (EPC) scenario gave increased biogas production and also notably decreased aeration consumption, leading to a positive energy balance. Both USS and EPC scenarios also showed increased stability of plant operation, with smaller daily averages of total nitrogen and phosphorus. In this context, USS and EPC results demonstrated that the coupled USS + EPC scenario and its combinations with agricultural spreading of N-rich effluent and nitritation/anaerobic deammonification could present an energy-positive balance with respectively 27% and 33% lower energy requirements and an increase in biogas production of 23%, compared to the reference scenario. The coupled scenarios also presented lesser environmental impacts (reduction of 31% and 39% in total endpoint impacts) along with effluent quality well within the specified limits. The marked environmental performance (reduction of global warming) when nitrogen is used

  3. [Long-term mechanical circulatory support in 2014: A real alternative to heart transplantation?].

    PubMed

    Flécher, Erwan

    2014-01-01

    Cardiac transplantation remains the gold standard for end stage heart failure however results of long-term mechanical circulatory support have dramatically improved over the last 10years. One should now clearly consider a left ventricular assist device as bridge to transplant or destination therapy in refractory isolated left heart failure. Mechanical biventricular support remains more challenging with lower survival and may be proposed as bridge to transplant. Correct patient's selection and appropriate follow-up are mandatory in such critical patients. PMID:24933679

  4. The Alternative complex III: properties and possible mechanisms for electron transfer and energy conservation.

    PubMed

    Refojo, Patrícia N; Teixeira, Miguel; Pereira, Manuela M

    2012-10-01

    Alternative complexes III (ACIII) are recently identified membrane-bound enzymes that replace functionally the cytochrome bc(1/)b(6)f complexes. In general, ACIII are composed of four transmembrane proteins and three peripheral subunits that contain iron-sulfur centers and C-type hemes. ACIII are built by a combination of modules present in different enzyme families, namely the complex iron-sulfur molybdenum containing enzymes. In this article a historical perspective on the investigation of ACIII is presented, followed by an overview of the present knowledge on these enzymes. Electron transfer pathways within the protein are discussed taking into account possible different locations (cytoplasmatic or periplasmatic) of the iron-sulfur containing protein and their contribution to energy conservation. In this way several hypotheses for energy conservation modes are raised including linear and bifurcating electron transfer pathways. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

  5. Structural differences within the loop E motif imply alternative mechanisms of viroid processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Viroids replicate via a rolling circle mechanism, and cleavage/ligation requires extensive rearrangement of the highly base-paired native structure. For Potato spindle tuber viroid (PSTVd), the switch from cleavage to ligation is driven by the change from a multi-branched tetraloop structure to a l...

  6. Introducing Mechanics: II. Towards a Justified Choice between Alternative Theories of Motion

    ERIC Educational Resources Information Center

    Emmett, Katrina; Klaassen, Kees; Eijkelhof, Harrie

    2009-01-01

    In an earlier article we presented an innovative approach for introducing mechanics at upper secondary level based on the idea of tapping core causal knowledge, and we described the working of the first part of the module. In this article we describe the second part of the module, in which we make use of the students' intuitive plausibility…

  7. CCDs in the Mechanics Lab--A Competitive Alternative? (Part I).

    ERIC Educational Resources Information Center

    Pinto, Fabrizio

    1995-01-01

    Reports on the implementation of a relatively low-cost, versatile, and intuitive system to teach basic mechanics based on the use of a Charge-Coupled Device (CCD) camera and inexpensive image-processing and analysis software. Discusses strengths and limitations of CCD imaging technologies. (JRH)

  8. Alternative Mechanisms to Encourage Individual Contributions to Vocational Education and Training

    ERIC Educational Resources Information Center

    Haukka, Sandra; Keating, Jack; Lamb, Stephen

    2004-01-01

    Financing vocational education and training, as part of Australia's commitment to lifelong learning, will become a greater challenge as increased spending on other public services, such as health and welfare caused by an aging population, constrains government education expenditure. This report examines a range of mechanisms to encourage…

  9. Linguistic Alternatives to Quantitative Research Strategies. Part One: How Linguistic Mechanisms Advance Research Outcomes

    ERIC Educational Resources Information Center

    Yeager, Joseph; Sommer, Linda

    2007-01-01

    Combining psycholinguistic technologies and systems analysis created advances in motivational profiling and numerous new behavioral engineering applications. These advances leapfrog many mainstream statistical research methods, producing superior research results via cause-effect language mechanisms. Entire industries explore motives ranging from…

  10. Degradation mechanism of over-charged LiCoO2/mesocarbon microbeads battery during shallow depth of discharge cycling

    NASA Astrophysics Data System (ADS)

    Zhang, Lingling; Ma, Yulin; Cheng, Xinqun; Cui, Yingzhi; Guan, Ting; Gao, Yunzhi; Du, Chunyu; Yin, Geping; Lin, Feng; Nordlund, Dennis

    2016-10-01

    LiCoO2/mesocarbon microbeads (MCMB) batteries are over-charged to different voltage (4.4 V, 4.5 V, 4.6 V, and 4.7 V, respectively) for ten times, and then are cycled 1000 times for shallow depth of discharge. The morphology, structure, and electrochemical performance of the electrode materials were studied in detail in order to identify the capacity fading mechanism of over-charged battery after long-term cycling. The cycling performances of LiCoO2/MCMB batteries are gradually aggravated with the increase of over-charging voltage and the degradation mechanism is diverse upon the degree of over-charging. The capacity fading after long-term cycling of battery over-charged to 4.6 V or 4.7 V is mainly attributed to the cathodes. Soft X-ray absorption spectroscopy (XAS) demonstrates that the lower valence state of cobalt exists on the surface of the LiCoO2 after serious over-charging (4.6 V or 4.7 V), and cobalt is dissolved then deposited on the anode according to the result of energy dispersive spectrometry (EDS). However, after shallow over-charging (4.4 V or 4.5 V), the capacity deterioration is proposed as the loss of active lithium, presented by the generation of the SEI film on the anode, which is verified by water washed tests.

  11. Inducing myoblast re-entry into the cell cycle: a potential mechanism for laser-enhanced skeletal muscle regeneration

    NASA Astrophysics Data System (ADS)

    Liu, T.; Fang, Y.; Zhang, C. P.; Chen, P.; Wang, C. Z.; Kang, H. X.; Shen, B. J.; Liang, J.; Fu, X. B.

    2014-09-01

    This study investigated the effect of low-level laser irradiation (LLLI) on the cell cycle and proliferative activity of cultured myoblasts, and sought to elucidate the possible cellular mechanism by which LLLI promotes the regeneration of skeletal muscle in vivo. Primary myoblasts isolated from rat hindlegs were irradiated with helium-neon laser light at different energy densities. Distributions of cell-cycle subpopulations and the expression of cell-cycle regulatory proteins in myoblasts were assessed using flow cytometric analysis and western blot assay. It was found that laser irradiation stimulated cell-cycle entry; induced the expression of cyclin A and cyclin D; and increased cell proliferation index and bromodeoxyuridine incorporation as compared to the unirradiated control cells, indicating LLLI augmented the number of proliferative myoblasts in the S phase and G2/M phase of the cell cycle. These results suggest that LLLI at certain fluxes and wavelengths could activate quiescent myoblasts, leading to cell division and facilitating new myofiber formation. This could contribute to the improvement of skeletal muscle regeneration following trauma and myopathic diseases.

  12. Blandford-Znajek mechanism in black holes in alternative theories of gravity

    NASA Astrophysics Data System (ADS)

    Pei, Guancheng; Nampalliwar, Sourabh; Bambi, Cosimo; Middleton, Matthew J.

    2016-10-01

    According to the Blandford-Znajek mechanism, black hole jets are powered by the rotational energy of the compact object. In this work, we consider the possibility that the metric around black holes may not be described by the Kerr solution and we study how this changes the Blandford-Znajek model. If the Blandford-Znajek mechanism is responsible for the formation of jets, the estimate of the jet power in combination with another measurement can test the nature of black hole candidates and constrain possible deviations from the Kerr solution. However, this approach might become competitive with respect to other techniques only when it will be possible to have measurements much more precise than those available today.

  13. Alternative mechanism for bacteriophage adsorption to the motile bacterium Caulobacter crescentus.

    PubMed

    Guerrero-Ferreira, Ricardo C; Viollier, Patrick H; Ely, Bert; Poindexter, Jeanne S; Georgieva, Maria; Jensen, Grant J; Wright, Elizabeth R

    2011-06-14

    2D and 3D cryo-electron microscopy, together with adsorption kinetics assays of Cb13 and CbK phage-infected Caulobacter crescentus, provides insight into the mechanisms of infection. Cb13 and CbK actively interact with the flagellum and subsequently attach to receptors on the cell pole. We present evidence that the first interaction of the phage with the bacterial flagellum takes place through a filament on the phage head. This contact with the flagellum facilitates concentration of phage particles around the receptor (i.e., the pilus portals) on the bacterial cell surface, thereby increasing the likelihood of infection. Phage head filaments have not been well characterized and their function is described here. Phage head filaments may systematically underlie the initial interactions of phages with their hosts in other systems and possibly represent a widespread mechanism of efficient phage propagation.

  14. Weaning from mechanical ventilation: why are we still looking for alternative methods?

    PubMed

    Frutos-Vivar, F; Esteban, A

    2013-12-01

    Most patients who require mechanical ventilation for longer than 24 hours, and who improve the condition leading to the indication of ventilatory support, can be weaned after passing a first spontaneous breathing test. The challenge is to improve the weaning of patients who fail that first test. We have methods that can be referred to as traditional, such as the T-tube, pressure support or synchronized intermittent mandatory ventilation (SIMV). In recent years, however, new applications of usual techniques as noninvasive ventilation, new ventilation methods such as automatic tube compensation (ATC), mandatory minute ventilation (MMV), adaptive support ventilation or automatic weaning systems based on pressure support have been described. Their possible role in weaning from mechanical ventilation among patients with difficult or prolonged weaning remains to be established.

  15. Crystal structure of A. aeolicus LpxC with bound product suggests alternate deacetylation mechanism.

    PubMed

    Miller, Matthew D; Gao, Ning; Ross, Philip L; Olivier, Nelson B

    2015-09-01

    UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is the first committed step to form lipid A, an essential component of the outer membrane of Gram-negative bacteria. As it is essential for the survival of many pathogens, LpxC is an attractive target for antibacterial therapeutics. Herein, we report the product-bound co-crystal structure of LpxC from the acheal Aquifex aeolicus solved to 1.6 Å resolution. We identified interactions by hydroxyl and hydroxymethyl substituents of the product glucosamine ring that may enable new insights to exploit waters in the active site for structure-based design of LpxC inhibitors with novel scaffolds. By using this product structure, we have performed quantum mechanical modeling on the substrate in the active site. Based on our results and published experimental data, we propose a new mechanism that may lead to a better understanding of LpxC catalysis and inhibition.

  16. Weaning from mechanical ventilation: why are we still looking for alternative methods?

    PubMed

    Frutos-Vivar, F; Esteban, A

    2013-12-01

    Most patients who require mechanical ventilation for longer than 24 hours, and who improve the condition leading to the indication of ventilatory support, can be weaned after passing a first spontaneous breathing test. The challenge is to improve the weaning of patients who fail that first test. We have methods that can be referred to as traditional, such as the T-tube, pressure support or synchronized intermittent mandatory ventilation (SIMV). In recent years, however, new applications of usual techniques as noninvasive ventilation, new ventilation methods such as automatic tube compensation (ATC), mandatory minute ventilation (MMV), adaptive support ventilation or automatic weaning systems based on pressure support have been described. Their possible role in weaning from mechanical ventilation among patients with difficult or prolonged weaning remains to be established. PMID:23084120

  17. Alternative mechanisms of increased eggshell hardness of avian brood parasites relative to host species

    PubMed Central

    Igic, Branislav; Braganza, Kim; Hyland, Margaret M.; Silyn-Roberts, Heather; Cassey, Phillip; Grim, Tomas; Rutila, Jarkko; Moskát, Csaba; Hauber, Mark E.

    2011-01-01

    Obligate brood parasitic birds lay their eggs in nests of other species and parasite eggs typically have evolved greater structural strength relative to host eggs. Increased mechanical strength of the parasite eggshell is an adaptation that can interfere with puncture ejection behaviours of discriminating hosts. We investigated whether hardness of eggshells is related to differences between physical and chemical traits from three different races of the parasitic common cuckoo Cuculus canorus, and their respective hosts. Using tools developed for materials science, we discovered a novel correlate of increased strength of parasite eggs: the common cuckoo's egg exhibits a greater microhardness, especially in the inner region of the shell matrix, relative to its host and sympatric non-host species. We then tested predictions of four potential mechanisms of shell strength: (i) increased relative thickness overall, (ii) greater proportion of the structurally harder shell layers, (iii) higher concentration of inorganic components in the shell matrix, and (iv) elevated deposition of a high density compound, MgCO3, in the shell matrix. We confirmed support only for hypothesis (i). Eggshell characteristics did not differ between parasite eggs sampled from different host nests in distant geographical sites, suggesting an evolutionarily shared microstructural mechanism of stronger parasite eggshells across diverse host-races of brood parasitic cuckoos. PMID:21561966

  18. Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Ortega, Pablo; Mignot, Juliette; Swingedouw, Didier; Sévellec, Florian; Guilyardi, Eric

    2015-09-01

    Understanding the preferential timescales of variability in the North Atlantic, usually associated with the Atlantic meridional overturning circulation (AMOC), is essential for the prospects for decadal prediction. However, the wide variety of mechanisms proposed from the analysis of climate simulations, potentially dependent on the models themselves, has stimulated the debate of which processes take place in reality. One mechanism receiving increasing attention, identified both in idealized models and observations, is a westward propagation of subsurface buoyancy anomalies that impact the AMOC through a basin-scale intensification of the zonal density gradient, enhancing the northward transport via thermal wind balance. In this study, we revisit a control simulation from the Institut Pierre-Simon Laplace Coupled Model 5A (IPSL-CM5A), characterized by a strong AMOC periodicity at 20 years, previously explained by an upper ocean-atmosphere-sea ice coupled mode driving convection activity south of Iceland. Our study shows that this mechanism interacts constructively with the basin-wide propagation in the subsurface. This constructive feedback may explain why bi-decadal variability is so intense in this coupled model as compared to others.

  19. Nonribosomal peptide synthetase with a unique iterative-alternative-optional mechanism catalyzes amonabactin synthesis in Aeromonas.

    PubMed

    Esmaeel, Qassim; Chevalier, Mickael; Chataigné, Gabrielle; Subashkumar, Rathinasamy; Jacques, Philippe; Leclère, Valérie

    2016-10-01

    Based on the exploration of data generated by genome sequencing, a bioinformatics approach has been chosen to identify the biosynthetic pathway of the siderophores produced by Aeromonas species. The amonabactins, considered as a virulence factor, represent a family of four variants of catechol peptidic siderophores containing Dhb, Lys, Gly, and an aromatic residue either Trp or Phe in a D-configuration. The synthesis operon is constituted of seven genes named amoCEBFAGH and is iron-regulated. The cluster includes genes encoding proteins involved in the synthesis and incorporation of the Dhb monomer, and genes encoding specific nonribosomal peptide synthetases, which are responsible for the building of the peptidic moiety. The amonabactin assembly line displays a still so far not described atypical mode of synthesis that is iterative, alternative, and optional. A disruption mutant in the adenylation domain of AmoG was unable to synthesize any amonabactin and to grow in iron stress conditions while a deletion of amoH resulted in the production of only two over the four forms. The amo cluster is widespread among most of the Aeromonas species, only few species produces the enterobactin siderophore.

  20. Nonribosomal peptide synthetase with a unique iterative-alternative-optional mechanism catalyzes amonabactin synthesis in Aeromonas.

    PubMed

    Esmaeel, Qassim; Chevalier, Mickael; Chataigné, Gabrielle; Subashkumar, Rathinasamy; Jacques, Philippe; Leclère, Valérie

    2016-10-01

    Based on the exploration of data generated by genome sequencing, a bioinformatics approach has been chosen to identify the biosynthetic pathway of the siderophores produced by Aeromonas species. The amonabactins, considered as a virulence factor, represent a family of four variants of catechol peptidic siderophores containing Dhb, Lys, Gly, and an aromatic residue either Trp or Phe in a D-configuration. The synthesis operon is constituted of seven genes named amoCEBFAGH and is iron-regulated. The cluster includes genes encoding proteins involved in the synthesis and incorporation of the Dhb monomer, and genes encoding specific nonribosomal peptide synthetases, which are responsible for the building of the peptidic moiety. The amonabactin assembly line displays a still so far not described atypical mode of synthesis that is iterative, alternative, and optional. A disruption mutant in the adenylation domain of AmoG was unable to synthesize any amonabactin and to grow in iron stress conditions while a deletion of amoH resulted in the production of only two over the four forms. The amo cluster is widespread among most of the Aeromonas species, only few species produces the enterobactin siderophore. PMID:27531515

  1. Influence of Different Thermo-mechanical Cycling Routes on Recovery Stresses of Annealed NiTi Wires

    NASA Astrophysics Data System (ADS)

    Yan, X. J.; Ge, Y. L.; Van Humbeeck, J.

    2016-01-01

    In this study, the influence of different thermo-mechanical cycling routes on recovery stresses of annealed NiTi wires has been investigated by using a dynamic mechanical analyzer. The as-received wire was annealed in Argon atmosphere in the temperature range of 350 to 900 °C. Differential scanning calorimeter was used to study the martensite transformation. In route I, the sample is deformed to 2% pre-strain and recovery stress is measured after unloading. In route II, the sample undergoes 3% deformation followed by a free shape recovery and then is reloaded to 2% pre-strain and recovery stress is measured after unloading. In route III, the sample undergoes a constrained thermal cycling at 3% pre-strain followed by a free shape recovery and then recovery stress is measured at 2% pre-strain. The results show that both route II and III can improve the recovery stresses. Route III has higher recovery stresses than route II for samples annealed at 550-700 °C. The improvements of recovery stresses under route II and III are partly attributed to the decrease of A s temperatures after thermo-mechanical cycling. Such information is essential for the proper use of NiTi alloys in smart structures, intelligent controllers, and memory devices.

  2. Structure of the voltage-gated K⁺ channel Eag1 reveals an alternative voltage sensing mechanism.

    PubMed

    Whicher, Jonathan R; MacKinnon, Roderick

    2016-08-12

    Voltage-gated potassium (K(v)) channels are gated by the movement of the transmembrane voltage sensor, which is coupled, through the helical S4-S5 linker, to the potassium pore. We determined the single-particle cryo-electron microscopy structure of mammalian K(v)10.1, or Eag1, bound to the channel inhibitor calmodulin, at 3.78 angstrom resolution. Unlike previous K(v) structures, the S4-S5 linker of Eag1 is a five-residue loop and the transmembrane segments are not domain swapped, which suggest an alternative mechanism of voltage-dependent gating. Additionally, the structure and position of the S4-S5 linker allow calmodulin to bind to the intracellular domains and to close the potassium pore, independent of voltage-sensor position. The structure reveals an alternative gating mechanism for K(v) channels and provides a template to further understand the gating properties of Eag1 and related channels. PMID:27516594

  3. ss-siRNAs allele selectively inhibit ataxin-3 expression: multiple mechanisms for an alternative gene silencing strategy.

    PubMed

    Liu, Jing; Yu, Dongbo; Aiba, Yuichiro; Pendergraff, Hannah; Swayze, Eric E; Lima, Walt F; Hu, Jiaxin; Prakash, Thazha P; Corey, David R

    2013-11-01

    Single-stranded silencing RNAs (ss-siRNAs) provide an alternative approach to gene silencing. ss-siRNAs combine the simplicity and favorable biodistribution of antisense oligonucleotides with robust silencing through RNA interference (RNAi). Previous studies reported potent and allele-selective inhibition of human huntingtin expression by ss-siRNAs that target the expanded CAG repeats within the mutant allele. Mutant ataxin-3, the genetic cause of Machado-Joseph Disease, also contains an expanded CAG repeat. We demonstrate here that ss-siRNAs are allele-selective inhibitors of ataxin-3 expression and then redesign ss-siRNAs to optimize their selectivity. We find that both RNAi-related and non-RNAi-related mechanisms affect gene expression by either blocking translation or affecting alternative splicing. These results have four broad implications: (i) ss-siRNAs will not always behave similarly to analogous RNA duplexes; (ii) the sequences surrounding CAG repeats affect allele-selectivity of anti-CAG oligonucleotides; (iii) ss-siRNAs can function through multiple mechanisms and; and (iv) it is possible to use chemical modification to optimize ss-siRNA properties and improve their potential for drug discovery.

  4. τ-lepton as a Composition of Massless Preons: an Alternative to Higgs Mechanism

    NASA Astrophysics Data System (ADS)

    Goncharov, Yuri P.

    2015-09-01

    Within the framework of the confinement mechanism proposed earlier by the author in QCD the problem of masses for fundamental fermions in particle physics is discussed by the example of τ-lepton τ -. It is shown that the observed parameters of τ-lepton such as its mass and magnetic moment can be obtained in a preon model dynamically due to a preon gauge interaction. The radius of τ-lepton is also estimated. Under the circumstances preons might be massless in virtue of existence of the nonzero chiral limit for the preon interaction energy.

  5. Soil organic carbon enrichment of dust emissions: Magnitude, mechanisms and its implications for the carbon cycle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon-dioxide (CO2), to the atmosphere. Understanding the magnitu...

  6. Thermal Cycling and Degradation Mechanisms of Compressive Mica-based Seals for Solid Oxide Fuel Cells

    SciTech Connect

    Chou, Yeong-Shyung ); Stevenson, Jeffry W. )

    2002-11-14

    Thermal cycling was conducted on the compressive mica seals at 800 degrees C in air. Thin ({approx}0-1 mm) Muscovite mica was pressed between a metal pipe and an alumina substrate and tested for leak rates at a stress of 100 psi in the plain (mica only) and the hybrid design.

  7. Gas-mediated vitreous compression: an experimental alternative to mechanized vitrectomy.

    PubMed

    Thresher, R J; Ehrenberg, M; Machemer, R

    1984-01-01

    We have developed a simple technique in rabbit and baboon eyes that utilizes intravitreally injected perfluoropropane gas, which expands slowly to efficiently compress and displace nearly completely the vitreous body. There is cataract formation after extended contact of the gas bubble with the lens. However, it is rapidly reversible by reducing the duration of lens contact (gas-fluid exchange) and by using young animals. No long-term alterations in intraocular pressure or retinal function were observed, as determined by electroretinography, during the 4-month test period. Gross examination and scanning electron microscopy revealed that the vitreous cavity, shortly after full expansion of the gas bubble, was practically free of collagen. The vitreous body had been detached from most of the retina and compressed into a collagenous strand between the optic nerve head and lens in the rabbit eyes, and there was also a dense collagen accumulation on the inferior retinal surface and anterior vitreous base in the rabbits and the baboon. Large areas of the retina and medullary wings were stripped of overlying collagen. By the end of 4 months, the compressed vitreous body had expanded to become an irregular structure that remained separated from the retina in areas of previous detachment. Mechanized vitrectomy is a difficult procedure often needed in experimental work. We believe that the vitreous compression and gas-fluid exchange technique is a valid alterative to a mechanical approach. We also believe that we have a model that simulates the human situation of posterior vitreous detachment and vitreous syneresis.

  8. Mindfulness-Based Exposure Strategies as a Transdiagnostic Mechanism of Change: An Exploratory Alternating Treatment Design.

    PubMed

    Brake, C Alex; Sauer-Zavala, Shannon; Boswell, James F; Gallagher, Matthew W; Farchione, Todd J; Barlow, David H

    2016-03-01

    The present study explored whether distress reduction in response to strong negative emotions, a putative transdiagnostic mechanism of action, is facilitated by mindfulness strategies. Seven patients (mean age=31.14years, SD=12.28, range 19-48 years, 43% female, 86% Caucasian) with heterogeneous anxiety disorders (i.e., panic disorder with or without agoraphobia, social anxiety, generalized anxiety) were assigned a randomized order of weeklong blocks utilizing either mindfulness- or avoidance-based strategies while ascending a 6-week emotion exposure hierarchy. Participants completed three exposures per block and provided distress and avoidance use ratings following each exposure. Anxiety severity, distress aversion, and distraction/suppression tendencies were also assessed at baseline and the conclusion of each block. Visual, descriptive, and effect size results showing exposures utilizing mindfulness were associated with higher overall distress levels, compared with those utilizing avoidance. Within blocks, the majority of participants exhibited declining distress levels when employing mindfulness strategies, as opposed to more static distress levels in the avoidance condition. Systematic changes in anxiety severity, distress aversion, and distraction/suppression were not observed. These results suggest mindfulness strategies may be effective in facilitating emotion exposure; however, a minimum dosage may be necessary to overcome initial distress elevation. Potential transdiagnostic change mechanisms and clinical implications are discussed. PMID:26956654

  9. Redox mechanism as alternative to ligand binding for receptor activation delivering disregulated cellular signals.

    PubMed

    Nakashima, I; Pu, M Y; Nishizaki, A; Rosila, I; Ma, L; Katano, Y; Ohkusu, K; Rahman, S M; Isobe, K; Hamaguchi, M

    1994-02-01

    Cross-linking with specific ligand is a general requirement for ordered activation of cell surface receptors. In this study we demonstrated a novel pathway for disregulated receptor activation through a redox mechanism. Treatment of murine thymocytes or spleen cells with thiol-reactive HgCl2, a known inducer of autoimmune proliferative lymphocyte disorders in rodents, was found to induce tyrosine phosphorylation of several cellular proteins, which was up to 100 times as extensive as that triggered by stimulation with antireceptor antibody or mitogen. Through the cross-linkage by thiol-reactive bivalent mercury, transmembrane CD4, CD3, and CD45 and glycosylphosphatidylinositol-anchored Thy-1 were aggregated together on thymocytes or T lymphocytes. Along with the aggregation of Thy-1 and CD4, nonreceptor protein tyrosine kinase p56lck was aggregated and activated. These events were linked to extensive protein tyrosine phosphorylation, which was visualized as a well localized spot beneath the membrane. Under appropriate conditions, this novel pathway of multiple receptor aggregation delivered a disregulated signal into T lymphocytes, which cross-talked to the antireceptor antibody-induced signal, for prolonged cell proliferation and IL-2 production. These results suggest a novel mechanism of disregulation of the ligand-dependent receptor function.

  10. Mechanisms of G1 cell cycle arrest and apoptosis in myeloma cells induced by hybrid-compound histone deacetylase inhibitor

    SciTech Connect

    Fujii, Seiko; Okinaga, Toshinori; Ariyoshi, Wataru; Takahashi, Osamu; Iwanaga, Kenjiro; Nishino, Norikazu; Tominaga, Kazuhiro; Nishihara, Tatsuji

    2013-05-10

    Highlights: •Novel histone deacetylase inhibitor Ky-2, remarkably inhibits myeloma cell growth. •Ky-2 demonstrates no cytotoxicity against normal lymphocytic cells. •Ky-2 induces cell cycle arrest through the cell cycle-associated proteins. •Ky-2 induces Bcl-2-inhibitable apoptosis through a caspase-dependent cascade. -- Abstract: Objectives: Histone deacetylase (HDAC) inhibitors are new therapeutic agents, used to treat various types of malignant cancers. In the present study, we investigated the effects of Ky-2, a hybrid-compound HDAC inhibitor, on the growth of mouse myeloma cells. Materials and methods: Myeloma cells, HS-72, P3U1, and mouse normal cells were used in this study. Effect of HDAC inhibitors on cell viability was determined by WST-assay and trypan blue assay. Cell cycle was analyzed using flow cytometer. The expression of cell cycle regulatory and the apoptosis associated proteins were examined by Western blot analysis. Hoechst’s staining was used to detect apoptotic cells. Results: Our findings showed that Ky-2 decreased the levels of HDACs, while it enhanced acetylation of histone H3. Myeloma cell proliferation was inhibited by Ky-2 treatment. Interestingly, Ky-2 had no cytotoxic effects on mouse normal cells. Ky-2 treatment induced G1-phase cell cycle arrest and accumulation of a sub-G1 phase population, while Western blotting analysis revealed that expressions of the cell cycle-associated proteins were up-regulated. Also, Ky-2 enhanced the cleavage of caspase-9 and -3 in myeloma cells, followed by DNA fragmentation. In addition, Ky-2 was not found to induce apoptosis in bcl-2 overexpressing myeloma cells. Conclusion: These findings suggest that Ky-2 induces apoptosis via a caspase-dependent cascade and Bcl-2-inhibitable mechanism in myeloma cells.

  11. A Comparison between Mechanisms of Multi-Alternative Perceptual Decision Making: Ability to Explain Human Behavior, Predictions for Neurophysiology, and Relationship with Decision Theory.

    PubMed

    Ditterich, Jochen

    2010-01-01

    While there seems to be relatively wide agreement about perceptual decision making relying on integration-to-threshold mechanisms, proposed models differ in a variety of details. This study compares a range of mechanisms for multi-alternative perceptual decision making, including integration with and without leakage, feedforward and feedback inhibition for mediating the competition between integrators, as well as linear and non-linear mechanisms for combining signals across alternatives. It is shown that a number of mechanisms make very similar predictions for the decision behavior and are therefore able to explain previously published data from a multi-alternative perceptual decision task. However, it is also demonstrated that the mechanisms differ in their internal dynamics and therefore make different predictions for neuorphysiological experiments. The study further addresses the relationship of these mechanisms with decision theory and statistical testing and analyzes their optimality.

  12. Coding Psychological Constructs in Text Using Mechanical Turk: A Reliable, Accurate, and Efficient Alternative.

    PubMed

    Tosti-Kharas, Jennifer; Conley, Caryn

    2016-01-01

    In this paper we evaluate how to effectively use the crowdsourcing service, Amazon's Mechanical Turk (MTurk), to content analyze textual data for use in psychological research. MTurk is a marketplace for discrete tasks completed by workers, typically for small amounts of money. MTurk has been used to aid psychological research in general, and content analysis in particular. In the current study, MTurk workers content analyzed personally-written textual data using coding categories previously developed and validated in psychological research. These codes were evaluated for reliability, accuracy, completion time, and cost. Results indicate that MTurk workers categorized textual data with comparable reliability and accuracy to both previously published studies and expert raters. Further, the coding tasks were performed quickly and cheaply. These data suggest that crowdsourced content analysis can help advance psychological research. PMID:27303321

  13. Coding Psychological Constructs in Text Using Mechanical Turk: A Reliable, Accurate, and Efficient Alternative

    PubMed Central

    Tosti-Kharas, Jennifer; Conley, Caryn

    2016-01-01

    In this paper we evaluate how to effectively use the crowdsourcing service, Amazon's Mechanical Turk (MTurk), to content analyze textual data for use in psychological research. MTurk is a marketplace for discrete tasks completed by workers, typically for small amounts of money. MTurk has been used to aid psychological research in general, and content analysis in particular. In the current study, MTurk workers content analyzed personally-written textual data using coding categories previously developed and validated in psychological research. These codes were evaluated for reliability, accuracy, completion time, and cost. Results indicate that MTurk workers categorized textual data with comparable reliability and accuracy to both previously published studies and expert raters. Further, the coding tasks were performed quickly and cheaply. These data suggest that crowdsourced content analysis can help advance psychological research. PMID:27303321

  14. Pathological display of affect in patients with depression and right frontal brain damage. An alternative mechanism.

    PubMed

    Ross, E D; Stewart, R S

    1987-03-01

    Two patients are reported with the acute onset of pathological crying following right inferior frontal brain damage. Both had severe endogenous depression and neither had pseudobulbar palsy. These and other cases argue that two organic brain diseases--one structural and the other "physiopharmacological"--may interact to produce pathological display of affect that cannot be accounted for by traditional neurological explanations. A pharmacological mechanism for the rapid amelioration of pathological affect by tricyclic medications and its possible relationship to the newly discovered descending motor systems of the brain that use norepinephrine and serotonin as neurotransmitters is offered. These cases also suggest that pathological affect is a valuable clinical indicator of an underlying major depression in some brain-injured patients. PMID:3819712

  15. Home composting as an alternative treatment option for organic household waste in Denmark: An environmental assessment using life cycle assessment-modelling

    SciTech Connect

    Andersen, J.K.; Boldrin, A.; Christensen, T.H.; Scheutz, C.

    2012-01-15

    An environmental assessment of the management of organic household waste (OHW) was performed from a life cycle perspective by means of the waste-life cycle assessment (LCA) model EASEWASTE. The focus was on home composting of OHW in Denmark and six different home composting units (with different input and different mixing frequencies) were modelled. In addition, incineration and landfilling was modelled as alternatives to home composting. The most important processes contributing to the environmental impact of home composting were identified as greenhouse gas (GHG) emissions (load) and the avoided emissions in relation to the substitution of fertiliser and peat when compost was used in hobby gardening (saving). The replacement of fertiliser and peat was also identified as one of the most sensible parameters, which could potentially have a significant environmental benefit. Many of the impact categories (especially human toxicity via water (HTw) and soil (HTs)) were affected by the heavy metal contents of the incoming OHW. The concentrations of heavy metals in the compost were below the threshold values for compost used on land and were thus not considered to constitute a problem. The GHG emissions were, on the other hand, dependent on the management of the composting units. The frequently mixed composting units had the highest GHG emissions. The environmental profiles of the home composting scenarios were in the order of -2 to 16 milli person equivalents (mPE) Mg{sup -1} wet waste (ww) for the non-toxic categories and -0.9 to 28 mPE Mg{sup -1} ww for the toxic categories. Home composting performed better than or as good as incineration and landfilling in several of the potential impact categories. One exception was the global warming (GW) category, in which incineration performed better due to the substitution of heat and electricity based on fossil fuels.

  16. Home composting as an alternative treatment option for organic household waste in Denmark: An environmental assessment using life cycle assessment-modelling.

    PubMed

    Andersen, J K; Boldrin, A; Christensen, T H; Scheutz, C

    2012-01-01

    An environmental assessment of the management of organic household waste (OHW) was performed from a life cycle perspective by means of the waste-life cycle assessment (LCA) model EASEWASTE. The focus was on home composting of OHW in Denmark and six different home composting units (with different input and different mixing frequencies) were modelled. In addition, incineration and landfilling was modelled as alternatives to home composting. The most important processes contributing to the environmental impact of home composting were identified as greenhouse gas (GHG) emissions (load) and the avoided emissions in relation to the substitution of fertiliser and peat when compost was used in hobby gardening (saving). The replacement of fertiliser and peat was also identified as one of the most sensible parameters, which could potentially have a significant environmental benefit. Many of the impact categories (especially human toxicity via water (HTw) and soil (HTs)) were affected by the heavy metal contents of the incoming OHW. The concentrations of heavy metals in the compost were below the threshold values for compost used on land and were thus not considered to constitute a problem. The GHG emissions were, on the other hand, dependent on the management of the composting units. The frequently mixed composting units had the highest GHG emissions. The environmental profiles of the home composting scenarios were in the order of -2 to 16 milli person equivalents (mPE) Mg(-1) wet waste (ww) for the non-toxic categories and -0.9 to 28mPEMg(-1) ww for the toxic categories. Home composting performed better than or as good as incineration and landfilling in several of the potential impact categories. One exception was the global warming (GW) category, in which incineration performed better due to the substitution of heat and electricity based on fossil fuels.

  17. Al-Li alloy AA2198's very high cycle fatigue crack initiation mechanism and its fatigue thermal effect

    NASA Astrophysics Data System (ADS)

    Xu, Luopeng; Cao, Xiaojian; Chen, Yu; Wang, Qingyuan

    2015-10-01

    AA2198 alloy is one of the third generation Al-Li alloys which have low density, high elastic modulus, high specific strength and specific stiffness. Compared With the previous two generation Al-Li alloys, the third generation alloys have much improved in alloys strength, corrosion resistance and weldable characteristic. For these advantages, the third generation Al-Li alloys are used as aircraft structures, such as C919 aviation airplane manufactured by China and Russia next generation aviation airplane--MS-21. As we know, the aircraft structures are usually subjected to more than 108 cycles fatigue life during 20-30 years of service, however, there is few reported paper about the third generation Al-Li alloys' very high cycle fatigue(VHCF) which is more than 108 cycles fatigue. The VHCF experiment of AA2198 have been carried out. The two different initiation mechanisms of fatigue fracture have been found in VHCF. The cracks can initiate from the interior of the testing material with lower stress amplitude and more than 108 cycles fatigue life, or from the surface or subsurface of material which is the dominant reason of fatigue failures. During the experiment, the infrared technology is used to monitor the VHCF thermal effect. With the increase of the stress, the temperature of sample is also rising up, increasing about 15 °C for every 10Mpa. The theoretical thermal analysis is also carried out.

  18. Life-Cycle Cost and Risk Analysis of Alternative Configurations for Shipping Low-Level Radioactive Waste to the Nevada Test Site

    SciTech Connect

    PM Daling; SB Ross; BM Biwer

    1999-12-17

    The Nevada Test Site (NTS) is a major receiver of low-level radioactive waste (LLW) for disposal. Currently, all LLW received at NTS is shipped by truck. The trucks use highway routes to NTS that pass through the Las Vegas Valley and over Hoover Dam, which is a concern of local stakeholder groups in the State of Nevada. Rail service offers the opportunity to reduce transportation risks and costs, according to the Waste Management Programmatic Environmental Impact Statement (WM-PEIS). However, NTS and some DOE LLW generator sites are not served with direct rail service so intermodal transport is under consideration. Intermodal transport involves transport via two modes, in this case truck and rail, from the generator sites to NTS. LLW shipping containers would be transferred between trucks and railcars at intermodal transfer points near the LLW generator sites, NTS, or both. An Environmental Assessment (EA)for Intermodal Transportation of Low-Level Radioactive Waste to the Nevada Test Site (referred to as the NTSIntermodal -M) has been prepared to determine whether there are environmental impacts to alterations to the current truck routing or use of intermodal facilities within the State of Nevada. However, an analysis of the potential impacts outside the State of Nevada are not addressed in the NTS Intermodal EA. This study examines the rest of the transportation network between LLW generator sites and the NTS and evaluates the costs, risks, and feasibility of integrating intermodal shipments into the LLW transportation system. This study evaluates alternative transportation system configurations for NTS approved and potential generators based on complex-wide LLW load information. Technical judgments relative to the availability of DOE LLW generators to ship from their sites by rail were developed. Public and worker risk and life-cycle cost components are quantified. The study identifies and evaluates alternative scenarios that increase the use of rail (intermodal

  19. Extreme events and the terrestrial carbon cycle - mechanisms, processes and impacts on different ecosystem types-

    NASA Astrophysics Data System (ADS)

    Frank, Dorothea; Reichstein, Markus

    2013-04-01

    Severe droughts, heat waves, extreme precipitation or storms can impact the structure, composition, and functioning of terrestrial ecosystems and thus their carbon cycling and carbon sequestration potential. Besides direct impacts on the carbon fluxes of photosynthesis and respiration, extreme events may also trigger further partially lagged phenomena such as heat wave and drought related fires, pest and pathogen outbreaks following heavy storm caused windthrow or drought stress reduced plant health. Extreme events have the potential to cause rapid carbon losses from accumulated stocks, as well as long-lasting impacts on the carbon cycle due to direct and lagged effects on plant growth and mortality, going often beyond the duration of the extreme event itself. Extreme events have the potential to impact the terrestrial ecosystem carbon balance through a single factor or as a combination of factors, and forests, grassland and croplands are differently affected by the various types of extremes.

  20. Designing instruction to support mechanical reasoning: Three alternatives in the simple machines learning environment

    NASA Astrophysics Data System (ADS)

    McKenna, Ann Frances

    2001-07-01

    Creating a classroom environment that fosters a productive learning experience and engages students in the learning process is a complex endeavor. A classroom environment is dynamic and requires a unique synergy among students, teacher, classroom artifacts and events to achieve robust understanding and knowledge integration. This dissertation addresses this complex issue by developing, implementing, and investigating the simple machines learning environment (SIMALE) to support students' mechanical reasoning and understanding. SIMALE was designed to support reflection, collaborative learning, and to engage students in generative learning through multiple representations of concepts and successive experimentation and design activities. Two key components of SIMALE are an original web-based software tool and hands-on Lego activities. A research study consisting of three treatment groups was created to investigate the benefits of hands-on and web-based computer activities on students' analytic problem solving ability, drawing/modeling ability, and conceptual understanding. The study was conducted with two populations of students that represent a diverse group with respect to gender, ethnicity, academic achievement and social/economic status. One population of students in this dissertation study participated from the Mathematics, Engineering, and Science Achievement (MESA) program that serves minorities and under-represented groups in science and mathematics. The second group was recruited from the Academic Talent Development Program (ATDP) that is an academically competitive outreach program offered through the University of California at Berkeley. Results from this dissertation show success of the SIMALE along several dimensions. First, students in both populations achieved significant gains in analytic problem solving ability, drawing/modeling ability, and conceptual understanding. Second, significant differences that were found on pre-test measures were eliminated

  1. Numerical evaluation of mechanisms driving Early Jurassic changes in global carbon cycling

    SciTech Connect

    Beerling, D.J.; Brentnall, S.J.

    2007-03-15

    The Early Jurassic (early Toarcian, ca. 183 Ma) carbon cycle perturbation is characterized by aabout -5 parts per thousand {delta} {sup 13}C excursion in the exogenic carbon reservoirs, a 1000 ppm rise in atmospheric CO{sub 2}, and a 6-7 degrees warming. Two proposed explanations for this presumed global carbon cycle perturbation are the liberation of massive amounts of isotopically light CH4 from (1) Gondwanan coals by heating during the intrusive eruption of the Karoo-Ferrar large igneous province (LIP) or (2) the thermal dissociation of gas hydrates. Carbon cycle modeling indicates that the release of CH4 from Gondwanan coals synchronous with the eruption of the Karoo-Ferrar LIP fails to reproduce the magnitude or timing of the CO{sub 2} and {delta} {sup 13}C excursions. However, sensitivity analyses constrained by a marine cyclostratigraphically dated {delta}{sup 13}C record indicate that both features of geologic record can be explained with the huge input of about 15,340-24,750 Gt C over about 220 k.y., a result possibly pointing to the involvement of hydrothermal vent complexes in the Karoo Basin. The simulated release of > 6000 Gt C from gas hydrates also reproduces aspects of the early Toarcian rock record, but the large mass involved raises fundamental questions about its formation, storage, and release.

  2. An alternate mechanism of abortive release marked by the formation of very long abortive transcripts.

    PubMed

    Chander, Monica; Austin, Karyn M; Aye-Han, Nwe-Nwe; Sircar, Piya; Hsu, Lilian M

    2007-11-01

    The Esigma70-dependent N25 promoter is rate-limited at promoter escape. Here, RNA polymerase repeatedly initiates and aborts transcription, giving rise to a ladder of short RNAs 2-11 nucleotides long. Certain mutations in the initial transcribed sequence (ITS) of N25 lengthen the abortive initiation program, resulting in the release of very long abortive transcripts (VLATs) 16-19 nucleotides long. This phenomenon is completely dependent on sequences within the first 20 bases of the ITS since altering sequences downstream of +20 has no effect on their formation. VLAT formation also requires strong interactions between RNA polymerase and the promoter. Mutations that change the -35 and -10 hexamers and the intervening 17 base pair spacer away from consensus decrease the probability of aborting at positions +16 to +19. An unusual characteristic of the VLATs is their undiminished levels in the presence of GreB, which rescues abortive RNAs (mechanism distinct from backtracking, which we propose entails polymerase molecules hyper forward translocating during the promoter escape transition. We discuss how certain features in the ITS, when combined with the N25 promoter, may lead to hyper forward translocation and abortive release at VLAT positions.

  3. Photofunctionalization of Titanium: An Alternative Explanation of Its Chemical-Physical Mechanism

    PubMed Central

    Pompella, Alfonso; Kubacki, Jerzy; Szade, Jacek; Roy, Robert A.; Hedzelek, Wieslaw

    2016-01-01

    Objectives To demonstrate that titanium implant surfaces as little as 4 weeks from production are contaminated by atmospheric hydrocarbons. This phenomenon, also known as biological ageing can be reversed by UVC irradiation technically known as photofunctionalization. To propose a new model from our experimental evidence to explain how the changes in chemical structure of the surface will affect the adsorption of amino acids on the titanium surface enhancing osteointegration. Methods In our study XPS and AES were used to analyze the effects of UVC irradiation (photofunctionalization) in reversing biological ageing of titanium. SEM was used to analyze any possible effects on the topography of the surface. Results UVC irradiation was able to reverse biological ageing of titanium by greatly reducing the amount of carbon contamination present on the implant surface by up to 4 times, while the topography of the surface was not affected. UVC photon energy reduces surface H2O and increases TiOH with many –OH groups being produced. These groups explain the super-hydrophilic effect from photofunctionalization when these groups come into contact with water. Significance Photofunctionalization has proven to be a valid method to reduce the amount of hydrocarbon contamination on titanium dental implants and improve biological results. The chemisorption mechanisms of amino acids, in our study, are dictated by the chemical structure and electric state present on the surface, but only in the presence of an also favourable geometrical composition at the atomical level. PMID:27309723

  4. Nanobacteria: An alternative mechanism for pathogenic intra- and extracellular calcification and stone formation

    PubMed Central

    Kajander, E. Olavi; Çiftçioglu, Neva

    1998-01-01

    Calcium phosphate is deposited in many diseases, but formation mechanisms remain speculative. Nanobacteria are the smallest cell-walled bacteria, only recently discovered in human and cow blood and commercial cell culture serum. In this study, we identified with energy-dispersive x-ray microanalysis and chemical analysis that all growth phases of nanobacteria produce biogenic apatite on their cell envelope. Fourier transform IR spectroscopy revealed the mineral as carbonate apatite. The biomineralization in cell culture media resulted in biofilms and mineral aggregates closely resembling those found in tissue calcification and kidney stones. In nanobacteria-infected fibroblasts, electron microscopy revealed intra- and extracellular acicular crystal deposits, stainable with von Kossa staining and resembling calcospherules found in pathological calcification. Previous models for stone formation have led to an hypothesis that elevated pH due to urease and/or alkaline phosphatase activity is a lithogenic factor. Our results indicate that carbonate apatite can be formed without these factors at pH 7.4, at physiological phosphate and calcium concentrations. Nanobacteria can produce apatite in media mimicking tissue fluids and glomerular filtrate and provide a unique model for in vitro studies on calcification. PMID:9653177

  5. A Homemade Snare: An Alternative Method for Mechanical Removal of Dirofilaria immitis in Dogs.

    PubMed

    Alho, Ana Margarida; Fiarresga, António; Landum, Miguel; Lima, Clara; Gamboa, Óscar; Meireles, José; Sales Luís, José; Madeira de Carvalho, Luís

    2016-01-01

    Canine dirofilariosis is a life-threatening parasitic disease that is increasingly reported worldwide. Once diagnosed the main treatment goals are to improve the animal's clinical condition and to eliminate all life stages of the parasite with minimal posttreatment side effects. This can be achieved through mechanical, surgical, or chemotherapeutical approaches. Currently, manual extraction is the preferred method to remove adult heartworms due to its diminished invasiveness, reduced damage to the vascular endothelium, and shortened anaesthesia duration. However, it remains an expensive technique that can be highly traumatic. To address this issue, a nontraumatic homemade catheter-guided snare was developed for heartworm removal by adapting and folding a 0.014-inch coronary wire (BMW, Abbott Vascular). Transvenous heartworm extraction was performed on a dog severely infected with adult heartworms by inserting the modified snare into a 6-F Judkins right coronary guiding catheter BMW (Cordis) and advancing it into the right ventricle under fluoroscopic guidance. Fifteen adult specimens of Dirofilaria immitis were successfully extracted from the pulmonary artery and right ventricle without complications. To assure the death of both larvae and adults, postoperative treatment was successfully managed using ivermectin, doxycycline, and melarsomine, with no recurrence after surgery.

  6. A Homemade Snare: An Alternative Method for Mechanical Removal of Dirofilaria immitis in Dogs

    PubMed Central

    Fiarresga, António; Landum, Miguel; Lima, Clara; Gamboa, Óscar; Meireles, José; Sales Luís, José; Madeira de Carvalho, Luís

    2016-01-01

    Canine dirofilariosis is a life-threatening parasitic disease that is increasingly reported worldwide. Once diagnosed the main treatment goals are to improve the animal's clinical condition and to eliminate all life stages of the parasite with minimal posttreatment side effects. This can be achieved through mechanical, surgical, or chemotherapeutical approaches. Currently, manual extraction is the preferred method to remove adult heartworms due to its diminished invasiveness, reduced damage to the vascular endothelium, and shortened anaesthesia duration. However, it remains an expensive technique that can be highly traumatic. To address this issue, a nontraumatic homemade catheter-guided snare was developed for heartworm removal by adapting and folding a 0.014-inch coronary wire (BMW, Abbott Vascular). Transvenous heartworm extraction was performed on a dog severely infected with adult heartworms by inserting the modified snare into a 6-F Judkins right coronary guiding catheter BMW (Cordis) and advancing it into the right ventricle under fluoroscopic guidance. Fifteen adult specimens of Dirofilaria immitis were successfully extracted from the pulmonary artery and right ventricle without complications. To assure the death of both larvae and adults, postoperative treatment was successfully managed using ivermectin, doxycycline, and melarsomine, with no recurrence after surgery. PMID:26981316

  7. A Homemade Snare: An Alternative Method for Mechanical Removal of Dirofilaria immitis in Dogs.

    PubMed

    Alho, Ana Margarida; Fiarresga, António; Landum, Miguel; Lima, Clara; Gamboa, Óscar; Meireles, José; Sales Luís, José; Madeira de Carvalho, Luís

    2016-01-01

    Canine dirofilariosis is a life-threatening parasitic disease that is increasingly reported worldwide. Once diagnosed the main treatment goals are to improve the animal's clinical condition and to eliminate all life stages of the parasite with minimal posttreatment side effects. This can be achieved through mechanical, surgical, or chemotherapeutical approaches. Currently, manual extraction is the preferred method to remove adult heartworms due to its diminished invasiveness, reduced damage to the vascular endothelium, and shortened anaesthesia duration. However, it remains an expensive technique that can be highly traumatic. To address this issue, a nontraumatic homemade catheter-guided snare was developed for heartworm removal by adapting and folding a 0.014-inch coronary wire (BMW, Abbott Vascular). Transvenous heartworm extraction was performed on a dog severely infected with adult heartworms by inserting the modified snare into a 6-F Judkins right coronary guiding catheter BMW (Cordis) and advancing it into the right ventricle under fluoroscopic guidance. Fifteen adult specimens of Dirofilaria immitis were successfully extracted from the pulmonary artery and right ventricle without complications. To assure the death of both larvae and adults, postoperative treatment was successfully managed using ivermectin, doxycycline, and melarsomine, with no recurrence after surgery. PMID:26981316

  8. Structural Insight into Archaic and Alternative Chaperone-Usher Pathways Reveals a Novel Mechanism of Pilus Biogenesis

    PubMed Central

    Pakharukova, Natalia; Garnett, James A.; Tuittila, Minna; Paavilainen, Sari; Diallo, Mamou; Xu, Yingqi; Matthews, Steve J.; Zavialov, Anton V.

    2015-01-01

    Gram-negative pathogens express fibrous adhesive organelles that mediate targeting to sites of infection. The major class of these organelles is assembled via the classical, alternative and archaic chaperone-usher pathways. Although non-classical systems share a wider phylogenetic distribution and are associated with a range of diseases, little is known about their assembly mechanisms. Here we report atomic-resolution insight into the structure and biogenesis of Acinetobacter baumannii Csu and Escherichia coli ECP biofilm-mediating pili. We show that the two non-classical systems are structurally related, but their assembly mechanism is strikingly different from the classical assembly pathway. Non-classical chaperones, unlike their classical counterparts, maintain subunits in a substantially disordered conformational state, akin to a molten globule. This is achieved by a unique binding mechanism involving the register-shifted donor strand complementation and a different subunit carboxylate anchor. The subunit lacks the classical pre-folded initiation site for donor strand exchange, suggesting that recognition of its exposed hydrophobic core starts the assembly process and provides fresh inspiration for the design of inhibitors targeting chaperone-usher systems. PMID:26587649

  9. Alternative mechanism of cholera toxin acquisition by Vibrio cholerae: generalized transduction of CTXPhi by bacteriophage CP-T1.

    PubMed

    Boyd, E F; Waldor, M K

    1999-11-01

    Horizontal transfer of genes encoding virulence factors has played a central role in the evolution of many pathogenic bacteria. The unexpected discovery that the genes encoding cholera toxin (ctxAB), the main cause of the profuse secretory diarrhea characteristic of cholera, are encoded on a novel filamentous phage named CTXPhi, has resulted in a renewed interest in the potential mechanisms of transfer of virulence genes among Vibrio cholerae. We describe here an alternative mechanism of cholera toxin gene transfer into nontoxigenic V. cholerae isolates, including strains that lack both the CTXPhi receptor, the toxin coregulated pilus (TCP), and attRS, the chromosomal attachment site for CTXPhi integration. A temperature-sensitive mutant of the V. cholerae generalized transducing bacteriophage CP-T1 (CP-T1ts) was used to transfer a genetically marked derivative of the CTX prophage into four nontoxigenic V. cholerae strains, including two V. cholerae vaccine strains. We demonstrate that CTXPhi transduced by CP-T1ts can replicate and integrate into these nontoxigenic V. cholerae strains with high efficiency. In fact, CP-T1ts transduces the CTX prophage preferentially when compared with other chromosomal markers. These results reveal a potential mechanism by which CTXPhi(+) V. cholerae strains that lack the TCP receptor may have arisen. Finally, these findings indicate an additional pathway for reversion of live-attenuated V. cholerae vaccine strains.

  10. Fatigue failure kinetics and structural changes in lead-free interconnects due to mechanical and thermal cycling

    NASA Astrophysics Data System (ADS)

    Fiedler, Brent Alan

    Environmental and human health concerns drove European parliament to mandate the Reduction of Hazardous Substances (RoHS) for electronics. This was enacted in July 2006 and has practically eliminated lead in solder interconnects. There is concern in the electronics packaging community because modern lead-free solder is rich in tin. Presently, near-eutectic tin-silver-copper solders are favored by industry. These solders are stiffer than the lead-tin near-eutectic alloys, have a higher melting temperature, fewer slip systems, and form intermetallic compounds (IMC) with Cu, Ni and Ag, each of which tend to have a negative effect on lifetime. In order to design more reliable interconnects, the experimental observation of cracking mechanisms is necessary for the correct application of existing theories. The goal of this research is to observe the failure modes resulting from mode II strain and to determine the damage mechanisms which describe fatigue failures in 95.5 Sn- 4.0 Ag - 0.5 Cu wt% (SAC405) lead-free solder interconnects. In this work the initiation sites and crack paths were characterized for SAC405 ball-grid array (BGA) interconnects with electroless-nickel immersion-gold (ENIG) pad-finish. The interconnects were arranged in a perimeter array and tested in fully assembled packages. Evaluation methods included monotonic and displacement controlled mechanical shear fatigue tests, and temperature cycling. The specimens were characterized using metallogaphy, including optical and electron microscopy as well as energy dispersive spectroscopy (EDS) and precise real-time electrical resistance structural health monitoring (SHM). In mechanical shear fatigue tests, strain was applied by the substrates, simulating dissimilar coefficients of thermal expansion (CTE) between the board and chip-carrier. This type of strain caused cracks to initiate in the soft Sn-rich solder and grow near the interface between the solder and intermetallic compounds (IMC). The growth near

  11. Do-or-die life cycles and diverse post-infection resistance mechanisms limit the evolution of parasite host ranges.

    PubMed

    Sieber, Michael; Gudelj, Ivana

    2014-04-01

    In light of the dynamic nature of parasite host ranges and documented potential for rapid host shifts, the observed high host specificity of most parasites remains an ecological paradox. Different variants of host-use trade-offs have become a mainstay of theoretical explanations of the prevalence of host specialism, but empirical evidence for such trade-offs is rare. We propose an alternative theory based on basic features of the parasite life cycle: host selection and subsequent intrahost replication. We introduce a new concept of effective burst size that accounts for the fact that successful host selection does not guarantee intrahost replication. Our theory makes a general prediction that a parasite will expand its host range if its effective burst size is positive. An in silico model of bacteria-phage coevolution verifies our predictions and demonstrates that the tendency for relatively narrow host ranges in parasites can be explained even in the absence of trade-offs. PMID:24495077

  12. Recognition of cycle mechanisms from study of single section: Lessons learned in Madera Formation, Sandia Mountains, New Mexico

    SciTech Connect

    Smith, G.A. )

    1989-09-01

    Eustasy, tectonics, and autogenic shoreline-related processes contribute to generation of transgressive-regressive (T-R) depositional cycles. Understanding the origin of a transgressive surface or a progradational sequence is critical for reconstructing paleogeography and predicting facies geometries. Knowledge of lateral extent and character of a cycle package provides the least ambiguous interpretation of the mechanism for changing shoreline position. In cases of poor exposure, low density of well data, or structural complexity, such interpretations must come from examination of single sections. This has been attempted during study of 300 m of cyclic carbonate/clastic sediments of the Pennsylvanian Madera Formation. There are 27 complete T-R cycles in the section, 15 in the lowest 120 m. The implied high frequency of the cycles (fourth order) implies that tectonism is less important than eustasy or autogenic processes in generating the cycles. Upward-coarsening delta-progradation sequences are rare. Most regressive sequences feature placement of delta-plain clastics on subtidal limestone without intervening delta-front or prodelta clastics. The uppermost meter of limestone shows evidence of abrupt shoaling; regressive grainstones underwent pervasive early cementation by meteoric waters. These relationships require that sea level fall. Most transgressive sequences exhibit ravinement surfaces with phosphate-bearing lags that truncate delta-plain facies and pass upward through thin transgressive grainstones to offshore lime mudstones. These may be of autogenic or eustatic origin. Few transgressive sequences show transitions from fluvial to shoreface clastics; transgression without diminished clastic input and accommodation of transgressive clastics would be favored by sea level rise. Most regressions appear to be eustatic, whereas the origin of most transgressions is ambiguous.

  13. Sperm quality in the alternative reproductive tactics of Atlantic salmon: the importance of the loaded raffle mechanism.

    PubMed Central

    Vladić, T. V.; Järvi, T.

    2001-01-01

    The outcome of sperm competition in species with alternative male reproductive strategies may be determined by fair or loaded raffle mechanisms. The sperm production and quality of male Atlantic salmon using alternative reproductive tactics were investigated in order to determine the relative importance of sperm quality for male reproductive success. Sexually mature resident parr males produced greater numbers of spermatozoa per millilitre of ejaculate and invested more in their gonads as a percentage of body mass than their anadromous counterparts. Parr males had greater proportions of motile spermatozoa and a greater sperm ATP content as compared with anadromous males. Parr males invested relatively more in sperm quality and sperm numbers after the effect of body size was accounted for. In fertilization experiments, parr males fertilized greater proportions of eggs than anadromous males. A polynomial model exhibited a trade-off between testes mass and ejaculate expenditure and explained 60% of the variation. These results establish that, in sperm competition with dominant males, parr males may compensate for behavioural subordinance by producing physiologically superior spermatozoa. PMID:11703878

  14. Control of cell cycle by metabolites of prostaglandin D2 through a non-cAMP mediated mechanism

    NASA Technical Reports Server (NTRS)

    Hughes-Fulford, M.; Fukushima, M.

    1993-01-01

    The dehydration products of PGD2, 9-deoxy-9 prostaglandin D2(PGJ2), 9-deoxy-delta 9, delta 12, delta 13 dehydroprostaglandin D2 (delta 12 PGJ2), and PGA2 all contain an unsaturated cyclopentenone structure which is characteristic of prostaglandins which effectively inhibit cell growth. It has been suggested that the action of the inhibitory prostaglandins may be through a cAMP mechanism. In this study, we use S49 wild type (WT) and adenylate cyclase variant (cyc-) cells to show that PGD2 and PGJ2 are not acting via a cyclic AMP mechanism. First, the increase in cyclic AMP in wild type S-49 cells is not proportional to its effects on DNA synthesis. More importantly, when S-49 cyc- cells were exposed to PGJ2, the adenylate cyclase (cyc-) mutant had decreased DNA synthesis with no change in its nominal cAMP content. Short-term (2 hours or less) exposure of the cyc- cells to prostaglandin J2 caused an inhibition of DNA synthesis. PGJ2 caused cytolysis at high concentrations. Long-term exposure (>14 hrs) of the cells to PGJ2, delta 12PGJ2 or delta 12, delta 14PGJ2 caused a cell cycle arrest in G1 demonstrating a cell cycle specific mechanism of action for growth inhibition by naturally occurring biological products independent of cAMP.

  15. Mechanical, hormonal, and hypertrophic adaptations to 10 weeks of eccentric and stretch-shortening cycle exercise training in old males.

    PubMed

    Váczi, Márk; Nagy, Szilvia A; Kőszegi, Tamás; Ambrus, Míra; Bogner, Péter; Perlaki, Gábor; Orsi, Gergely; Tóth, Katalin; Hortobágyi, Tibor

    2014-10-01

    The growth promoting effects of eccentric (ECC) contractions are well documented but it is unknown if the rate of stretch per se plays a role in such muscular responses in healthy aging human skeletal muscle. We tested the hypothesis that exercise training of the quadriceps muscle with low rate ECC and high rate ECC contractions in the form of stretch-shortening cycles (SSCs) but at equal total mechanical work would produce rate-specific adaptations in healthy old males age 60-70. Both training programs produced similar improvements in maximal voluntary isometric (6%) and ECC torque (23%) and stretch-shortening cycle function (reduced contraction duration [24%] and enhanced elastic energy storage [12%]) (p<0.05). The rate of torque development increased 30% only after SSC exercise (p<0.05). Resting testosterone and cortisol levels were unchanged but after each program the acute exercise-induced cortisol levels were 12-15% lower (p<0.05). Both programs increased quadriceps size 2.5% (p<0.05). It is concluded that both ECC and SSC exercise training produces favorable adaptations in healthy old males' quadriceps muscle. Although the rate of muscle tension during the SSC vs. ECC contractions was about 4-fold greater, the total mechanical work seems to regulate the hypetrophic, hormonal, and most of the mechanical adaptations. However, SSC exercise was uniquely effective in improving a key deficiency of aging muscle, i.e., its ability to produce force rapidly.

  16. Mechanism of uncoupling in mitochondria: uncouplers as ionophores for cycling cations and protons.

    PubMed

    Kessler, R J; Tyson, C A; Green, D E

    1976-09-01

    Classical uncouplers such as 2,4-dinitrophenol have been shown to be ionophores with the capability for transporting monovalent or divalent cations with equal efficiency. The conditions appropriate for the maximal expression of this ionophoric capability have been explored. Two critical factors are the polarity of the organic phase and the pH of the aqueous phase that is equilibrated with the organic phase. The demonstrated cationic ionophoric capability of uncouplers, taken in conjunction with the known ability of uncouplers to cycle protons across a membrane phase, provides the experimental basis for the thesis that uncoupling of electron flow from ATP synthesis via classical uncouplers involves the substitution of one coupled process by another. Uncoupling thus reduces to the replacement of one driven reaction (ATP synthesis) by the driven reaction (cyclical transport) mediated by the uncoupler.

  17. Canard explosion of limit cycles in templator models of self-replication mechanisms

    NASA Astrophysics Data System (ADS)

    Brøns, Morten

    2011-04-01

    Templators are differential equation models for self-replicating chemical systems. Beutel and Peacock-López [J. Chem. Phys. 126, 125104 (2007)], 10.1063/1.2716396 have numerically analyzed a model for a cross-catalytic self-replicating system and found two cases of canard explosion, that is, a substantial change of amplitude of a limit cycle over a very short parameter interval. We show how the model can be reduced to a two-dimensional system and how canard theory for slow-fast equations can be applied to yield analytic information about the canard explosion. In particular, simple expressions for the parameter value where the canard explosion occurs are obtained. The connection to mixed-mode oscillations also observed in the model is briefly discussed.

  18. Mechanisms of Beat-to-Beat Regulation of Cardiac Pacemaker Cell Function by Ca2+ Cycling Dynamics

    PubMed Central

    Yaniv, Yael; Stern, Michael D.; Lakatta, Edward G.; Maltsev, Victor A.

    2013-01-01

    Whether intracellular Ca2+ cycling dynamics regulate cardiac pacemaker cell function on a beat-to-beat basis remains unknown. Here we show that under physiological conditions, application of low concentrations of caffeine (2–4 mM) to isolated single rabbit sinoatrial node cells acutely reduces their spontaneous action potential cycle length (CL) and increases Ca2+ transient amplitude for several cycles. Numerical simulations, using a modified Maltsev-Lakatta coupled-clock model, faithfully reproduced these effects, and also the effects of CL prolongation and dysrhythmic spontaneous beating (produced by cytosolic Ca2+ buffering) and an acute CL reduction (produced by flash-induced Ca2+ release from a caged Ca2+ buffer), which we had reported previously. Three contemporary numerical models (including the original Maltsev-Lakatta model) failed to reproduce the experimental results. In our proposed new model, Ca2+ releases acutely change the CL via activation of the Na+/Ca2+ exchanger current. Time-dependent CL reductions after flash-induced Ca2+ releases (the memory effect) are linked to changes in Ca2+ available for pumping into sarcoplasmic reticulum which, in turn, changes the sarcoplasmic reticulum Ca2+ load, diastolic Ca2+ releases, and Na+/Ca2+ exchanger current. These results support the idea that Ca2+ regulates CL in cardiac pacemaker cells on a beat-to-beat basis, and suggest a more realistic numerical mechanism of this regulation. PMID:24094396

  19. Single-nucleotide resolution mapping of the Gossypium raimondii transcriptome reveals a new mechanism for alternative splicing of introns.

    PubMed

    Li, Qin; Xiao, Guanghui; Zhu, Yu-Xian

    2014-05-01

    Alternative splicing (AS) is a vital genetic mechanism that enhances the diversity of eukaryotic transcriptomes. Here, we generated 8.3 Gb high-quality RNA-sequencing data from cotton (Gossypium raimondii) and performed a systematic, comparative analysis of AS events. We mapped 85% of the RNA-sequencing data onto the reference genome and identified 154368 splice junctions with 16437 as events in 10197 genes. Intron retention constituted the majority (40%) of all AS events in G. raimondii. Comparison across 11 eukaryote species showed that intron retention is the most common AS type in higher plants. Although transposable elements (TEs) were found in only 2.9% of all G. raimondii introns, they are present in 43% of the retained introns, suggesting that TE-insertion may be an important mechanism for intron retention during AS. The majority of the TE insertions are concentrated 0-40 nt upstream of the 3'-splice site, substantially altering the distribution of branch points from preferred positions and reducing the efficiency of intron splicing by decreasing RNA secondary structure flexibility. Our data suggest that TE-insertion-induced changes in branch point-site distribution are important for intron retention-type AS. Our findings may help explain the vast differences in intron-retention frequencies between vertebrates and higher plants.

  20. Effects of weak transcranial alternating current stimulation on brain activity-a review of known mechanisms from animal studies.

    PubMed

    Reato, Davide; Rahman, Asif; Bikson, Marom; Parra, Lucas C

    2013-01-01

    Rhythmic neuronal activity is ubiquitous in the human brain. These rhythms originate from a variety of different network mechanisms, which give rise to a wide-ranging spectrum of oscillation frequencies. In the last few years an increasing number of clinical research studies have explored transcranial alternating current stimulation (tACS) with weak current as a tool for affecting brain function. The premise of these interventions is that tACS will interact with ongoing brain oscillations. However, the exact mechanisms by which weak currents could affect neuronal oscillations at different frequency bands are not well known and this, in turn, limits the rational optimization of human experiments. Here we review the available in vitro and in vivo animal studies that attempt to provide mechanistic explanations. The findings can be summarized into a few generic principles, such as periodic modulation of excitability, shifts in spike timing, modulation of firing rate, and shifts in the balance of excitation and inhibition. These effects result from weak but simultaneous polarization of a large number of neurons. Whether this can lead to an entrainment or a modulation of brain oscillations, or whether AC currents have no effect at all, depends entirely on the specific dynamic that gives rise to the different brain rhythms, as discussed here for slow wave oscillations (∼1 Hz) and gamma oscillations (∼30 Hz). We conclude with suggestions for further experiments to investigate the role of AC stimulation for other physiologically relevant brain rhythms. PMID:24167483

  1. Gonadotropin-releasing hormone agonist trigger is a better alternative than human chorionic gonadotropin in PCOS undergoing IVF cycles for an OHSS Free Clinic: A Randomized control trial

    PubMed Central

    Krishna, Deepika; Dhoble, Snehal; Praneesh, Gautham; Rathore, Suvarna; Upadhaya, Amit; Rao, Kamini

    2016-01-01

    OBJECTIVE: The objective of this study is to evaluate if gonadotropin-releasing hormone agonist (GnRHa) trigger is a better alternative to human chorionic gonadotropin (hCG) in polycystic ovary syndrome (PCOS) of Indian origin undergoing in vitro fertilization (IVF) cycles with GnRH antagonist for the prevention of ovarian hyperstimulation syndrome (OHSS). DESIGN: Prospective randomized control trial. SETTING: Tertiary care center. MATERIALS AND METHODS: A total of 227 patients diagnosed with PCOS, undergoing IVF in an antagonist protocol were recruited and randomly assigned into two groups: Group A (study group): GnRHa trigger 0.2 mg (n = 92) and Group B (control group): 250 μg of recombinant hCG as trigger (n = 101) 35 h before oocyte retrieval. We chose segmentation strategy, freezing all embryos in both the groups. STATISTICAL ANALYSIS: Continuous variables were expressed as mean ± standard deviation independent sample t-test and Kolmogorov-Smirnov test were used for continuous variables which were normally distributed and Mann-Whitney U-test for data not normally distributed. MAIN OUTCOME MEASURES: Primary outcome: OHSS (mild, moderate, and severe) rates. Secondary outcomes: Maturity rate of the oocytes, fertilization rate, availability of top quality embryos on day 3 (Grade 1 and Grade 2). RESULTS The incidence of moderate to severe OHSS in the hCG group was 37.6% and 0% in the GnRHa group with P < 0.001. The GnRHa group had significantly more mature oocytes retrieved (19.1 ± 11.7 vs. 14.1 ± 4.3), more fertilized oocytes (15.6 ± 5.6 vs. 11.7 ± 3.6), and a higher number of top quality cleavage embryos on day 3 (12.9 ± 4.7 vs. 7.5 ± 4.3) than the hCG group. CONCLUSIONS: The most effective strategy which significantly eliminates the occurrence of OHSS in PCOS following ovarian stimulation in antagonist IVF cycles is the use of GnRHa trigger yielding more mature oocytes and good quality embryos when compared with hCG trigger. PMID:27803584

  2. Effect of thermo-mechanical cycling on zirconium hydride reorientation studied in situ with synchrotron X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.; Motta, Arthur T.; Daymond, Mark R.; Almer, Jonathan D.

    2013-09-01

    The circumferential hydrides normally present in nuclear reactor fuel cladding after reactor exposure may dissolve during drying for dry storage and re-precipitate when cooled under load into a more radial orientation, which could embrittle the fuel cladding. It is necessary to study the rates and conditions under which hydride reorientation may happen in order to assess fuel integrity in dry storage. The objective of this work is to study the effect of applied stress and thermal cycling on the hydride morphology in cold-worked stress-relieved Zircaloy-4 by combining conventional metallography and in situ X-ray diffraction techniques. Metallography is used to study the evolution of hydride morphology after several thermo-mechanical cycles. In situ X-ray diffraction performed at the Advanced Photon Source synchrotron provides real-time information on the process of hydride dissolution and precipitation under stress during several thermal cycles. The detailed study of diffracted intensity, peak position and full-width at half-maximum provides information on precipitation kinetics, elastic strains and other characteristics of the hydride precipitation process. The results show that thermo-mechanical cycling significantly increases the radial hydride fraction as well as the hydride length and connectivity. The radial hydrides are observed to precipitate at a lower temperature than circumferential hydrides. Variations in the magnitude and range of hydride strains due to reorientation and cycling have also been observed. These results are discussed in light of existing models and experiments on hydride reorientation. The study of hydride elastic strains during precipitation shows marked differences between circumferential and radial hydrides, which can be used to investigate the reorientation process. Cycling under stress above the threshold stress for reorientation drastically increases both the reoriented hydride fraction and the hydride size. The reoriented hydride

  3. Maternal effects mechanism of population cycling: a formidable competitor to the traditional predator–prey view

    PubMed Central

    Inchausti, Pablo; Ginzburg, Lev R.

    2009-01-01

    In the language of mathematics, one needs minimally two interacting variables (two dimensions) to describe repeatable periodic behaviour, and in the language of density dependence, one needs delayed, not immediate, density dependence to produce cyclicity. Neither language specifies the causal mechanism. There are two major potential mechanisms: exogenous mechanisms involving species interactions as in predator–prey or host–parasite, and endogenous mechanisms such as maternal effects where population growth results from the cross-generational transmission of individual quality. The species interactions view stemming from a major observation of Elton and a simultaneous independent theory by Lotka and Volterra is currently dominant. Most ecologists, when faced with cyclic phenomena, automatically look for an interacting species one step below or above in a food chain in order to find an explanation. Maternal effects hypothesis, verbally suggested in the 1950s, had only found its theoretical implementation in the 1990s. In a relatively short time, the degree of acceptance of this view grew to the level of a ‘minority opinion’ as evidenced by the widely used textbook of Begon et al. This short review attempts to describe the arguments for and against this internal two-dimensional approach. PMID:19324616

  4. Glucocorticoid receptor-mediated cell cycle arrest is achieved through distinct cell-specific transcriptional regulatory mechanisms.

    PubMed Central

    Rogatsky, I; Trowbridge, J M; Garabedian, M J

    1997-01-01

    Glucocorticoids inhibit proliferation of many cell types, but the events leading from the activated glucocorticoid receptor (GR) to growth arrest are not understood. Ectopic expression and activation of GR in human osteosarcoma cell lines U2OS and SAOS2, which lack endogenous receptors, result in a G1 cell cycle arrest. GR activation in U2OS cells represses expression of the cyclin-dependent kinases (CDKs) CDK4 and CDK6 as well as their regulatory partner, cyclin D3, leading to hypophosphorylation of the retinoblastoma protein (Rb). We also demonstrate a ligand-dependent reduction in the expression of E2F-1 and c-Myc, transcription factors involved in the G1-to-S-phase transition. Mitogen-activated protein kinase, CDK2, cyclin E, and the CDK inhibitors (CDIs) p27 and p21 are unaffected by receptor activation in U2OS cells. The receptor's N-terminal transcriptional activation domain is not required for growth arrest in U2OS cells. In Rb-deficient SAOS2 cells, however, the expression of p27 and p21 is induced upon receptor activation. Remarkably, in SAOS2 cells that express a GR deletion derivative lacking the N-terminal transcriptional activation domain, induction of CDI expression is abolished and the cells fail to undergo ligand-dependent cell cycle arrest. Similarly, murine S49 lymphoma cells, which, like SAOS2 cells, lack Rb, require the N-terminal activation domain for growth arrest and induce CDI expression upon GR activation. These cell-type-specific differences in receptor domains and cellular targets linking GR activation to cell cycle machinery suggest two distinct regulatory mechanisms of GR-mediated cell cycle arrest: one involving transcriptional repression of G1 cyclins and CDKs and the other involving enhanced transcription of CDIs by the activated receptor. PMID:9154817

  5. Effects of Thermal and Mechanical Load Cycling on the Dentin Microtensile Bond Strength of Single Bond-2

    PubMed Central

    Daneshkazemi, Alireza; Davari, Abdolrahim; Akbari, Mohammad Javad; Davoudi, Amin; Badrian, Hamid

    2015-01-01

    Background: Different studies have shown the uncertain effects of thermal cycling (TC) and mechanical load cycling (MC) on the dentin microtensile bond strength (µTBS) of composites. This study designed to investigate the effects of TC and MC on the dentin µTBS of single bond-2. Materials and Methods: Flat dentinal surface was prepared on 48 sound extracted human third molar teeth, and were bonded by single bond-2 adhesive and Z250 resin composite. The teeth were randomly divided into eight equal groups, according to the thermal/mechanical protocol. TC and MC were proceeded at 5-55°C and 90 N with 0.5 Hz. Then restorations were sectioned to shape the hour-glass form and subjected to µTBS testing at a speed of 0.5 mm/min. To evaluate the bonding failure, the specimens were observed under the scanning electron microscope. The results were statistically analyzed with analysis of variance, t-test, Tukey HSD and post-hoc by using SPSS software version 17 at a significant level of 0.05. Results: µTBS of all groups were significantly lower than the control group (P < 0.001). Adhesive failure was predominant in all groups and increased with TC and MC. Conclusions: TC and MC had an adverse effect on µTBS of the tested adhesive resin to dentin. PMID:26464532

  6. Targeting and functional mechanisms of the cytokinesis-related F-BAR protein Hof1 during the cell cycle.

    PubMed

    Oh, Younghoon; Schreiter, Jennifer; Nishihama, Ryuichi; Wloka, Carsten; Bi, Erfei

    2013-05-01

    F-BAR proteins are membrane-associated proteins believed to link the plasma membrane to the actin cytoskeleton in cellular processes such as cytokinesis and endocytosis. In the budding yeast Saccharomyces cerevisiae, the F-BAR protein Hof1 localizes to the division site in a complex pattern during the cell cycle and plays an important role in cytokinesis. However, the mechanisms underlying its localization and function are poorly understood. Here we show that Hof1 contains three distinct targeting domains that contribute to cytokinesis differentially. The N-terminal half of Hof1 localizes to the bud neck and the sites of polarized growth during the cell cycle. The neck localization is mediated mainly by an interaction between the second coiled-coil region in the N-terminus and the septin Cdc10, whereas the localization to the sites of polarized growth is mediated entirely by the F-BAR domain. In contrast, the C-terminal half of Hof1 interacts with Myo1, the sole myosin-II heavy chain in budding yeast, and localizes to the bud neck in a Myo1-dependent manner from the onset to the completion of cytokinesis. We also show that the SH3 domain in the C-terminus plays an important role in maintaining the symmetry of Myo1 ring constriction during cytokinesis and that Hof1 interacts with Chs2, a chitin synthase that is required for primary septum formation. Together these data define a mechanism that accounts for the localization of Hof1 during the cell cycle and suggest that Hof1 may function in cytokinesis by coupling actomyosin ring constriction to primary septum formation through interactions with Myo1 and Chs2. PMID:23468521

  7. Restoring grassland savannas from degraded pinyon-juniper woodlands: effects of mechanical overstory reduction and slash treatment alternatives.

    PubMed

    Brockway, Dale G; Gatewood, Richard G; Paris, Randi B

    2002-02-01

    Although the distribution and structure of pinyon-juiper woodlands in the southwestern United States are thought to be the result of historic fluctuations in regional climatic conditions, more recent increases in the areal extent, tree density, soil erosion rates and loss of understory plant diversity are attributed to heavy grazing by domestic livestock and interruption of the natural fire regime. Prior to 1850, many areas currently occupied by high-density pinyon-juniper woodlands, with their degraded soils and depauperate understories, were very likely savannas dominated by native grasses and forbs and containing sparse tree cover scattered across the landscape. The purpose of this study was to evaluate the effectiveness of mechanical overstory reduction and three slash treatment alternatives (removal, clustering and scattering) followed by prescribed fire as techniques for restoring grassland savannas from degraded woodlands. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry and erosion rates were measured prior to and for two years following experimental treatment in a degraded pinyon-juniper woodland in central New Mexico. Treatment resulted in a significant increase in the cover of native grasses and, to a lesser degree, forbs and shrubs. Plant species richness and diversity increased most on sites where slash was either completely removed or scattered to serve as a mulch. Although no changes in soil chemistry or plant nutrient status were observed, understory biomass increased over 200% for all harvest treatments and was significantly greater than controls. While treatment increased litter cover and decreased soil exposure, this improvement did not significantly affect soil loss rates. Even though all slash treatment alternatives increased the cover and biomass of native grasses, scattering slash across the site to serve as a mulch appears most beneficial to improving plant species diversity and conserving site resources

  8. Heteromeric amino acid transporters. In search of the molecular bases of transport cycle mechanisms.

    PubMed

    Palacín, Manuel; Errasti-Murugarren, Ekaitz; Rosell, Albert

    2016-06-15

    Heteromeric amino acid transporters (HATs) are relevant targets for structural studies. On the one hand, HATs are involved in inherited and acquired human pathologies. On the other hand, these molecules are the only known examples of solute transporters composed of two subunits (heavy and light) linked by a disulfide bridge. Unfortunately, structural knowledge of HATs is scarce and limited to the atomic structure of the ectodomain of a heavy subunit (human 4F2hc-ED) and distant prokaryotic homologues of the light subunits that share a LeuT-fold. Recent data on human 4F2hc/LAT2 at nanometer resolution revealed 4F2hc-ED positioned on top of the external loops of the light subunit LAT2. Improved resolution of the structure of HATs, combined with conformational studies, is essential to establish the structural bases for light subunit recognition and to evaluate the functional relevance of heavy and light subunit interactions for the amino acid transport cycle.

  9. Plumbagin induces cell death through a copper-redox cycle mechanism in human cancer cells.

    PubMed

    Nazeem, S; Azmi, Asfar S; Hanif, Sarmad; Ahmad, Aamir; Mohammad, Ramzi M; Hadi, S M; Kumar, K Sateesh

    2009-09-01

    Plumbagin, a naphthoquinone derived from the medicinal plant Plumbago zeylanica has been shown to exert anticancer and anti-proliferative activities in cells in culture as well as animal tumor models. In our previous paper, we have reported the cytotoxic action of plumbagin in plasmid pBR322 DNA as well as human peripheral blood lymphocytes through a redox mechanism involving copper. Copper has been shown to be capable of mediating the action of several plant-derived compounds through production of reactive oxygen species (ROS). The objective of the present study was to determine whether plumbagin induces apoptosis in human cancer cells through the same mechanism which we proposed earlier. Using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay, 3-(4,5-B-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for cell growth inhibition, histone/DNA ELISA, homogeneous caspase-3/7 assay for apoptosis as well as alkaline comet assay for DNA single-strand breaks detection in this report, we confirm that plumbagin causes effective cell growth inhibition, induces apoptosis and generates single-strand breaks in cancer cells. Incubation of cancer cells with scavengers of ROS and neocuproine inhibited the cytotoxic action of plumbagin proving that generation of ROS and Cu(I) are the critical mediators in plumbagin-induced cell growth inhibition. This study is the first to investigate the copper-mediated anticancer mechanism of plumbagin in human cancer cells and these properties of plumbagin could be further explored for the development of anticancer agents with higher therapeutic indices, especially for skin cancer.

  10. Left bundle branch block and mechanical events of the cardiac cycle.

    PubMed

    Hultgren, H N; Craige, E; Fujii, J; Nakamura, T; Bilisoly, J

    1983-10-01

    Left bundle branch block (LBBB) is associated with a prolongation of the interval from the QRS onset to the onset of left ventricular (LV) ejection. The locus and prevalence of specific sites of delay were examined in 56 patients with complete LBBB using echocardiography, phonocardiography and external pulse recordings. The results were compared with those in 52 control subjects without LBBB. The onset of the QRS complex was used as the initial reference point of measurement of time intervals. The following abnormalities were found in patients with LBBB: (1) delayed mitral valve closure (Q-MC greater than 0.08 second) was the major site of delay in 23% of patients; (2) prolongation of the LV isovolumetric contraction time (greater than 0.06 second) was the major site of delay in 41%; (3) both Q-MC and LV isovolumetric contraction time were prolonged in 18%; and (4) in 26% of patients the onset of ventricular contraction determined by the onset of the increase of the apex impulse was delayed (Q-VC greater than 0.07 second). The most common cause of delayed ejection was a prolonged LV isovolumetric contraction time, which occurred in 59% of patients. A control group of 20 patients with abnormal LV function but without LBBB had a low incidence of the 3 types of delay in LV ejection (0 to 15%). Thus, the major abnormalities in the cardiac cycle in LBBB are due to the conduction defect and not to LV dysfunction. The results of this study suggest the presence of variable abnormalities of conduction in complete LBBB. PMID:6624668

  11. Effects of bonding bakeout thermal cycles on pre- and post irradiation microstructures, physical, and mechanical properties of copper alloys

    SciTech Connect

    Singh, B.N.; Eldrup, M.; Toft, P.; Edwards, D.J.

    1996-10-01

    At present, dispersion strengthened (DS) copper is being considered as the primary candidate material for the ITER first wall and divertor components. Recently, it was agreed among the ITER parties that a backup alloy should be selected from the two well known precipitation hardened copper alloys, CuCrZr and CuNiBe. It was therefore decided to carry out screening experiments to simulate the effect of bonding and bakeout thermal cycles on microstructure, mechanical properties, and electrical resistivity of CuCrZr and CuNiBe alloys. On the basis of the results of these experiments, one of the two alloys will be selected as a backup material. Tensile specimens of CuCrZr and CuNiBe alloys were given various heat treatments corresponding to solution anneal, prime ageing, and bonding thermal cycle followed by reageing and the reactor bakeout treatment at 623K for 100 hours. Tensile specimens of the DS copper were also given the heat treatment corresponding to the bonding thermal cycle. A number of these heat treated specimens of CuCrZr, CuNiBe, and DS copper were neutron irradiated at 523K to a dose level of {approx}0.3 dpa (NRT) in the DR-3 reactor at Riso. Both unirradiated and irradiated specimens with the various heat treatments were tensile tested at 532K. The dislocation, precipitate and void microstructures and electrical resistivity of these specimens were also determined. Results of these investigations will be reported and discussed in terms of thermal and irradiation stability of precipitates and irradiation-induced precipitation and recovery of dislocation microstructure. Results show that the bonding and bakeout thermal cycles are not likely to have any serious deleterious effects on the performance of these alloys. The CuNiBe alloys were found to be susceptible to radiation-induced embrittlement, however, the exact mechanism is not yet known. It is thought that radiation-induced precipitation and segregation of the beryllium may be responsible.

  12. Discovery of causal mechanisms: Oxidative phosphorylation and the Calvin-Benson cycle.

    PubMed

    Scholl, Raphael; Nickelsen, Kärin

    2015-06-01

    We investigate the context of discovery of two significant achievements of twentieth century biochemistry: the chemiosmotic mechanism of oxidative phosphorylation (proposed in 1961 by Peter Mitchell) and the dark reaction of photosynthesis (elucidated from 1946 to 1954 by Melvin Calvin and Andrew A. Benson). The pursuit of these problems involved discovery strategies such as the transfer, recombination and reversal of previous causal and mechanistic knowledge in biochemistry. We study the operation and scope of these strategies by careful historical analysis, reaching a number of systematic conclusions: (1) even basic strategies can illuminate "hard cases" of scientific discovery that go far beyond simple extrapolation or analogy; (2) the causal-mechanistic approach to discovery permits a middle course between the extremes of a completely substrate-neutral and a completely domain-specific view of scientific discovery; (3) the existing literature on mechanism discovery underemphasizes the role of combinatorial approaches in defining and exploring search spaces of possible problem solutions; (4) there is a subtle interplay between a fine-grained mechanistic and a more coarse-grained causal level of analysis, and both are needed to make discovery processes intelligible. PMID:26013645

  13. Discovery of causal mechanisms: Oxidative phosphorylation and the Calvin-Benson cycle.

    PubMed

    Scholl, Raphael; Nickelsen, Kärin

    2015-06-01

    We investigate the context of discovery of two significant achievements of twentieth century biochemistry: the chemiosmotic mechanism of oxidative phosphorylation (proposed in 1961 by Peter Mitchell) and the dark reaction of photosynthesis (elucidated from 1946 to 1954 by Melvin Calvin and Andrew A. Benson). The pursuit of these problems involved discovery strategies such as the transfer, recombination and reversal of previous causal and mechanistic knowledge in biochemistry. We study the operation and scope of these strategies by careful historical analysis, reaching a number of systematic conclusions: (1) even basic strategies can illuminate "hard cases" of scientific discovery that go far beyond simple extrapolation or analogy; (2) the causal-mechanistic approach to discovery permits a middle course between the extremes of a completely substrate-neutral and a completely domain-specific view of scientific discovery; (3) the existing literature on mechanism discovery underemphasizes the role of combinatorial approaches in defining and exploring search spaces of possible problem solutions; (4) there is a subtle interplay between a fine-grained mechanistic and a more coarse-grained causal level of analysis, and both are needed to make discovery processes intelligible.

  14. Linking Self-Incompatibility, Dichogamy, and Flowering Synchrony in Two Euphorbia Species: Alternative Mechanisms for Avoiding Self-Fertilization?

    PubMed Central

    Narbona, Eduardo; Ortiz, Pedro L.; Arista, Montserrat

    2011-01-01

    Background Plant species have several mechanisms to avoid selfing such as dichogamy or a self-incompatibility response. Dichogamy in a single flower may reduce autogamy but, to avoid geitonogamy, plants must show flowering synchronization among all their flowers (i.e. synchronous dichogamy). It is hypothesized that one species would not simultaneously show synchronous dichogamy and self-incompatibility because they are redundant mechanisms to reduce selfing; however, this has not been accurately assessed. Methodology/Principal Findings This expectation was tested over two years in two natural populations of the closely related Mediterranean spurges Euphorbia boetica and E. nicaeensis, which completely avoid autogamy by protogyny at the cyathia level. Both spurges showed a high population synchrony (Z<79), and their inflorescences flower synchronously. In E. nicaeensis, there was no overlap among the cyathia in anthesis of successive inflorescence levels and the overlap between sexual phases of cyathia of the same inflorescence level was uncommon (4–16%). In contrast, E. boetica showed a high overlap among consecutive inflorescence levels (74–93%) and between sexual phases of cyathia of the same inflorescence level (48–80%). The flowering pattern of both spurges was consistent in the two populations and over the two successive years. A hand-pollination experiment demonstrated that E. nicaeensis was strictly self-compatible whereas E. boetica was partially self-incompatible. Conclusions/Significance We propose that the complex pattern of synchronized protogyny in E. nicaeensis prevents geitonogamous crosses and, consequently, avoids selfing and inbreeding depression. In E. boetica, a high probability of geitonogamous crosses may occur but, alternatively, this plant escapes selfing through a self-incompatibility response. We posit that synchronous dichogamy and physiological self-incompatibility do not co-occur in the same species because each process is

  15. PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms.

    PubMed

    Gisselsson, D; Hibbard, M K; Dal Cin, P; Sciot, R; Hsi, B L; Kozakewich, H P; Fletcher, J A

    2001-09-01

    Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.

  16. Leaching of biocides from polymer renders under wet/dry cycles--Rates and mechanisms.

    PubMed

    Styszko, Katarzyna; Bollmann, Ulla E; Bester, Kai

    2015-11-01

    In this study it was tested, which mechanism for the transport of biocides in polymeric renders is more relevant: (1) evaporative transports (meaning there is a flow of water through the material due to evaporation on the surface), which transports also the biocides to the surface, (2) transport through the polymer and (3) transport through water filled pores. It turned out that under the experimental conditions evaporative transport was not relevant, while transport through soaked (constantly wetted) renders was considerably faster than by other means. Additionally it turned out that also the equilibria were influenced by the water content. Differences in equilibria can be up to factor 10 between constantly wetted (soaked) and un-wetted materials. The two tested materials (one silicone and one acrylate render) had significantly different leaching behavior concerning equilibria and dynamics of mass flows, but for both the pre-wetted materials leached most. PMID:26210026

  17. Investigation of anticancer mechanism of oleuropein via cell cycle and apoptotic pathways in SH-SY5Y neuroblastoma cells.

    PubMed

    Seçme, Mücahit; Eroğlu, Canan; Dodurga, Yavuz; Bağcı, Gülseren

    2016-07-01

    Neuroblastoma is one of the most common types of pediatric tumors that can spread quickly in neuronal tissues. Oleuropein which is active compound of olive leaves, belongs to polyphenols group and has antioxidant, anti-microbial, anti-inflammatory, anti-hypertensive and anti-carcinogenic effects. The aim of the study is to determine the therapeutic effects of oleuropein on cell proliferation, invasion, colony formation, cell cycle and apoptotic mechanisms in SH-SY5Y neuroblastoma cell line under in vitro conditions. The effect of oleuropein on cell viability was determined by XTT method. 84 cell cycle control and 84 apoptosis related genes were evaluated by RT-PCR. Effects of oleuropein on apoptosis were researched by TUNEL assay. Protein expressions were determined by western blot analysis. Effects of oleuropein on cell invasion, colony formation and migration were detected by matrigel-chamber, colony formation assay and wound-healing assay, respectively. IC50 value of oleuropein in SH-SY5Y cells was detected as 350 μM at 48th hours. It is determined that oleuropein causes cell cycle arrest by down-regulating of CylinD1,CylinD2,CyclinD3,CDK4,CDK6 and up-regulating of p53 and CDKN2A, CDKN2B, CDKN1A gene expressions. Oleuropein also induces apoptosis by inhibiting of Bcl-2 and activating of Bax,caspase-9 and caspase-3 gene expressions. Apoptotic cell ratio was found 36.4 ± 3.27% in oleuropein dose group. Oleuropein decreased invasion in SH-SY5Y cells and suppressed colony numbers in ratio of 53.6 ± 4.71%.Our results demonstrated that oleuropein can be a therapeutic agent in the treatment of neuroblastoma.

  18. Structural evolution and the capacity fade mechanism upon long-term cycling in Li-rich cathode material.

    PubMed

    Song, Bohang; Liu, Zongwen; Lai, Man On; Lu, Li

    2012-10-01

    High capacity Li-rich layered cathode Li(Li(0.2)Mn(0.54)Ni(0.13)Co(0.13))O(2) and doped one are investigated to understand mechanisms of capacity fade as well as voltage decrease upon long-term cycling. Detailed electrochemical analysis reveals a phase-separation-like behavior with increase in the cycle number, which is responsible for gradual reduction in discharge voltage. X-ray photoelectron spectroscopy (XPS), transmission electron microscope coupled with energy dispersive X-ray spectroscopy (TEM-EDS) and inductively coupled plasma emission spectrometry (ICP) analysis results show increase in valence of transition metals on the surface of powder at a fully discharged state in addition to surface dissolution of Ni, leading to rapid capacity loss. High resolution transmission electron microscopy (HR-TEM) shows a phase transformation from original layered structure into spinel-like nano-domains in local structure. Though such an unexpected structural change is unfavorable because of lower output voltage, it is observed to be beneficial for high-rate performance.

  19. Capacity fading mechanism during long-term cycling of over-discharged LiCoO2/mesocarbon microbeads battery

    NASA Astrophysics Data System (ADS)

    Zhang, Lingling; Ma, Yulin; Cheng, Xinqun; Du, Chunyu; Guan, Ting; Cui, Yingzhi; Sun, Shun; Zuo, Pengjian; Gao, Yunzhi; Yin, Geping

    2015-10-01

    The LiCoO2/mesocarbon microbeads (MCMB) batteries are over-discharged to 102% DOD, 105% DOD and 115% DOD, respectively, then are fully charged and cycled 1000 times at 0.6 C with 30% DOD. The capacity fading mechanism during long-term cycling of over-discharged batteries is analyzed by electrochemical and physical characterization. No remarkable difference is found on the morphology of LiCoO2 material from SEM. However, copper is detected on anode over-discharged to 115% DOD by EDS and XRD. The structures of LiCoO2 and MCMB materials have almost no change according to the result of XRD test. The performance of MCMB material can be degraded by over-discharge, however the LiCoO2 material still keeps good performance. The capacity of MCMB electrode is improved after being washed with water to remove the SEI film, indicating that the capacity loss of MCMB electrode is mainly attributed to the increase of SEI film. The capacity deterioration of over-discharged battery is mainly caused by the dissolution of copper current collector and the deposition of Cu on the surface of anode during the following charging process. The copper deposited on the surface of anode can hinder the lithium intercalation into/de-intercalation from the anode and promote the increase of SEI film.

  20. Highly Dynamic Interactions Maintain Kinetic Stability of the ClpXP Protease During the ATP-Fueled Mechanical Cycle.

    PubMed

    Amor, Alvaro J; Schmitz, Karl R; Sello, Jason K; Baker, Tania A; Sauer, Robert T

    2016-06-17

    The ClpXP protease assembles in a reaction in which an ATP-bound ring hexamer of ClpX binds to one or both heptameric rings of the ClpP peptidase. Contacts between ClpX IGF-loops and clefts on a ClpP ring stabilize the complex. How ClpXP stability is maintained during the ATP-hydrolysis cycle that powers mechanical unfolding and translocation of protein substrates is poorly understood. Here, we use a real-time kinetic assay to monitor the effects of nucleotides on the assembly and disassembly of ClpXP. When ATP is present, complexes containing single-chain ClpX assemble via an intermediate and remain intact until transferred into buffers containing ADP or no nucleotides. ATP binding to high-affinity subunits of the ClpX hexamer prevents rapid dissociation, but additional subunits must be occupied to promote assembly. Small-molecule acyldepsipeptides, which compete with the IGF loops of ClpX for ClpP-cleft binding, cause exceptionally rapid dissociation of otherwise stable ClpXP complexes, suggesting that the IGF-loop interactions with ClpP must be highly dynamic. Our results indicate that the ClpX hexamer spends almost no time in an ATP-free state during the ATPase cycle, allowing highly processive degradation of protein substrates.

  1. Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 3: Energy conversion subsystems and components. Part 1: Bottoming cycles and materials of construction

    NASA Technical Reports Server (NTRS)

    Shah, R. P.; Solomon, H. D.

    1976-01-01

    Energy conversion subsystems and components were evaluated in terms of advanced energy conversion systems. Results of the bottoming cycles and materials of construction studies are presented and discussed.

  2. A mechanism for bacterial transformation of dimethylsulfide to dimethylsulfoxide: a missing link in the marine organic sulfur cycle.

    PubMed

    Lidbury, Ian; Kröber, Eileen; Zhang, Zhidong; Zhu, Yijun; Murrell, J Colin; Chen, Yin; Schäfer, Hendrik

    2016-09-01

    The volatile organosulfur compound, dimethylsulfide (DMS), plays an important role in climate regulation and global sulfur biogeochemical cycles. Microbial oxidation of DMS to dimethylsulfoxide (DMSO) represents a major sink of DMS in surface seawater, yet the underlying molecular mechanisms and key microbial taxa involved are not known. Here, we reveal that Ruegeria pomeroyi, a model marine heterotrophic bacterium, can oxidize DMS to DMSO using trimethylamine monooxygenase (Tmm). Purified Tmm oxidizes DMS to DMSO at a 1:1 ratio. Mutagenesis of the tmm gene in R. pomeroyi completely abolished DMS oxidation and subsequent DMSO formation. Expression of Tmm and DMS oxidation in R. pomeroyi is methylamine-dependent and regulated at the post-transcriptional level. Considering that Tmm is present in approximately 20% of bacterial cells inhabiting marine surface waters, particularly the marine Roseobacter clade and the SAR11 clade, our observations contribute to a mechanistic understanding of biological DMSO production in surface seawater. PMID:27114231

  3. Entropy production in mesoscopic stochastic thermodynamics: nonequilibrium kinetic cycles driven by chemical potentials, temperatures, and mechanical forces

    NASA Astrophysics Data System (ADS)

    Qian, Hong; Kjelstrup, Signe; Kolomeisky, Anatoly B.; Bedeaux, Dick

    2016-04-01

    Nonequilibrium thermodynamics (NET) investigates processes in systems out of global equilibrium. On a mesoscopic level, it provides a statistical dynamic description of various complex phenomena such as chemical reactions, ion transport, diffusion, thermochemical, thermomechanical and mechanochemical fluxes. In the present review, we introduce a mesoscopic stochastic formulation of NET by analyzing entropy production in several simple examples. The fundamental role of nonequilibrium steady-state cycle kinetics is emphasized. The statistical mechanics of Onsager’s reciprocal relations in this context is elucidated. Chemomechanical, thermomechanical, and enzyme-catalyzed thermochemical energy transduction processes are discussed. It is argued that mesoscopic stochastic NET in phase space provides a rigorous mathematical basis of fundamental concepts needed for understanding complex processes in chemistry, physics and biology. This theory is also relevant for nanoscale technological advances.

  4. Multiple ranges of flow rate with bistability and limit cycles for Schlögl's mechanism in a CSTR

    NASA Astrophysics Data System (ADS)

    Escher, Claus; Ross, John

    1983-10-01

    Continuous flow stirred tank reactor (CSTR) conditions are imposed upon Schlögl's trimolecular reaction mechanism A+2X ⇄ 3X and X ⇄ B. A nonzero constant flow rate (=inverse residence time) rather than constant concentrations of A,B forces the system far away from equilibrium. This change in constraints leads to some surprisingly complex features; first the system has bistability for separate ranges of flow rates, under constraints of all other parameters being fixed including the concentration of the chemical species in the input. This phenomena occurs even if the input contains A alone. Secondly, there occur limit cycle oscillations, but in that case the input has to include B or X as well as A.

  5. High temperature low-cycle fatigue mechanisms in single crystals of nickel-based superalloy Mar-M 200

    NASA Technical Reports Server (NTRS)

    Milligan, W. W.; Jayaraman, N.

    1984-01-01

    Twenty three high temperature low-cycle fatigue tests were conducted on single crystals of the nickel-based superalloy Mar-M 200. Tests were conducted at 760 and 870 C. SEM fractography and transmission electron microscopy were used to determine mechanisms responsible for the observed orientation dependent fatigue behavior. It has been concluded that the plastic characteristics of the alloy lead to orientation-dependent strain hardening and fatigue lives at 760 C. At 870 C, the elastic characteristics of the alloy dominated the behavior, even though the plastic strain ranges were about the same as they were at 760 C. This led to orientation-dependent fatigue lives, but the trends were not the same as they were at 760 C.

  6. Time course of neuro-mechanical changes underlying stretch-shortening cycle during intermittent exhaustive rebound exercise.

    PubMed

    Morio, Cédric; Chavet, Pascale; Androuet, Philippe; Foissac, Matthieu; Berton, Eric; Nicol, Caroline

    2011-09-01

    This study analysed the time course of neuro-mechanical changes underlying stretch-shortening cycle during intermittent exhaustive rebound exercise. On a sledge apparatus, ten subjects repeated until exhaustion a series of 30 unilateral submaximal rebounds, with intermediate 3-min rest periods. Rebound height, ground reaction force, 3D tibial acceleration and electromyographic activity of major lower limb muscles were recorded. A maximal drop jump test performed before and after the exhaustive exercise revealed a 10% drop in maximal stretch-shortening cycle (SSC) performance. Specific investigation of the neuro-mechanical changes along the exhaustive exercise included classical comparison of the first (BEG) and last (END) rebound series. From the initial accommodation phase, an optimized (OPTIM) series was individually determined as the first of at least two subsequent series with significantly shorter contact time than in the BEG series. The OPTIM series was reached after 3 ± 1 series, with associated increased lower limb stiffness during the braking phase and decreased muscle activities during the push-off. The major result was that the early (BEG-OPTIM) changes explained most of the BEG-END ones whereas the actual (OPTIM-END) fatigue effects remained quite limited. This confirmed our expectation that erroneous quantification of the SSC fatigue effects might be drawn when using the early beginning of rebound exercise on the sledge as a reference. Actual fatigue effects included medio-lateral instability as suggested by increased peroneus longus preactivation and medio-lateral tibial acceleration. The present methodology is thus considered as improving the distinction between SSC optimization and its deterioration with fatigue.

  7. Mechanisms involved in resveratrol-induced apoptosis and cell cycle arrest in prostate cancer-derived cell lines.

    PubMed

    Benitez, Dixan A; Pozo-Guisado, Eulalia; Alvarez-Barrientos, Alberto; Fernandez-Salguero, Pedro M; Castellón, Enrique A

    2007-01-01

    Resveratrol is a polyphenol found at high concentrations in grapes and red wine with reported anticarcinogenic effects. We studied the molecular mechanism of resveratrol-induced apoptosis and proliferation arrest in prostate derived cells PZ-HPV-7 (nontumorigenic line), LNCaP (androgen-sensitive cancer line), and PC-3 (androgen-insensitive cancer line). Apoptosis and cell cycle distribution were evaluated by flow cytometry and proliferation by MTT assay and direct cell counting. Caspases, bax, bcl-2, cyclins, Cdks, p53, p21, and p27 were measured by Western blot and kinase activities of cyclin/Cdk complexes by immunoprecipitation followed by kinase assays with appropriate substrates. Resveratrol induced a decrease in proliferation rates and an increase in apoptosis in cancer cell lines in a dose- and time-dependent manner. These effects were coincident with cell accumulation at the G0/G1 phase. In LNCaP and PC-3, the apoptosis induced by resveratrol was mediated by activation of caspases 9 and 3 and a change in the ratio of bax/bcl-2. Expressions of cyclin D1, E, and Cdk4 as well as cyclin D1/Cdk4 kinase activity were reduced by resveratrol only in LNCaP cells. In contrast, cyclin B and Cdk1 expression and cyclin B/Cdk1 kinase activity were decreased in both cell lines in the presence of resveratrol. However, modulator proteins p53, p21, and p27 were increased by resveratrol only in LNCaP cells. These effects probably result in the observed proliferation arrest and disruption of cell cycle control. In addition, the specific differences found between LNCaP and PC-3 suggest that resveratrol acts through different mechanisms upon the androgen or estrogen receptor cell status. PMID:17050787

  8. Mechanisms involved in resveratrol-induced apoptosis and cell cycle arrest in prostate cancer-derived cell lines.

    PubMed

    Benitez, Dixan A; Pozo-Guisado, Eulalia; Alvarez-Barrientos, Alberto; Fernandez-Salguero, Pedro M; Castellón, Enrique A

    2007-01-01

    Resveratrol is a polyphenol found at high concentrations in grapes and red wine with reported anticarcinogenic effects. We studied the molecular mechanism of resveratrol-induced apoptosis and proliferation arrest in prostate derived cells PZ-HPV-7 (nontumorigenic line), LNCaP (androgen-sensitive cancer line), and PC-3 (androgen-insensitive cancer line). Apoptosis and cell cycle distribution were evaluated by flow cytometry and proliferation by MTT assay and direct cell counting. Caspases, bax, bcl-2, cyclins, Cdks, p53, p21, and p27 were measured by Western blot and kinase activities of cyclin/Cdk complexes by immunoprecipitation followed by kinase assays with appropriate substrates. Resveratrol induced a decrease in proliferation rates and an increase in apoptosis in cancer cell lines in a dose- and time-dependent manner. These effects were coincident with cell accumulation at the G0/G1 phase. In LNCaP and PC-3, the apoptosis induced by resveratrol was mediated by activation of caspases 9 and 3 and a change in the ratio of bax/bcl-2. Expressions of cyclin D1, E, and Cdk4 as well as cyclin D1/Cdk4 kinase activity were reduced by resveratrol only in LNCaP cells. In contrast, cyclin B and Cdk1 expression and cyclin B/Cdk1 kinase activity were decreased in both cell lines in the presence of resveratrol. However, modulator proteins p53, p21, and p27 were increased by resveratrol only in LNCaP cells. These effects probably result in the observed proliferation arrest and disruption of cell cycle control. In addition, the specific differences found between LNCaP and PC-3 suggest that resveratrol acts through different mechanisms upon the androgen or estrogen receptor cell status.

  9. The thermal-mechanical evolution of crustal orogenic belts at convergent plate boundaries: A reappraisal of the orogenic cycle

    NASA Astrophysics Data System (ADS)

    Vanderhaeghe, Olivier

    2012-05-01

    Convergent plate boundaries are characterized by the development of crustal orogenic wedges and orogenic plateaus but also by gravitational collapse of previously thickened crust leading to the opening of intermontane and eventually oceanic back-arc basins. Foreland and extensional sedimentary basins in the plate boundary region are filled by the erosional products of the orogenic crust. Metamorphic rocks forming orogenic crust attest to burial and exhumation under contrasted geothermal gradients. These features portray the crustal orogenic cycle and are first-order indicators of the thermal and mechanical evolution of the crust within the plate boundary region. This evolution is controlled by complex interactions among (i) the dynamic balance among forces that arise from plate-tectonic, gravitational potential energy, and buoyancy, (ii) the thermal balance between deformation-induced and radioactive heat production and heat advection related to subduction, orogenic deformation, and magma transfer, and (iii) the mass transfer balance between uplift and erosion. To account for these geological characteristics, a generic model, that integrates results from physical modeling, is proposed for the thermal-mechanical evolution of crustal orogenic belts and for its implication in controlling the transition between the different phases of the orogenic cycle. In this model, the transition from low to high geothermal gradient is associated with increased heat production in the thickened crust owing to radioactive decay and deformation. Partial melting and rheologic weakening of the thermally mature thickened crust triggers gravity-driven lateral flow of the lower crust and controls the transition from wedge to orogenic plateau. Destruction of the orogenic crust is achieved in part by erosion but mostly by gravitational collapse. The style of extension is controlled by the rheology of the crust at the onset of gravitational collapse and its evolution as the crust thins and

  10. Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects. Final technical report, June 1992-January 1995

    SciTech Connect

    Bast, C.C.; Boyce, L.

    1995-01-01

    This report presents the results of both the fifth and sixth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA). The research included on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model`s empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for five variables, namely, high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect.

  11. Developmental mechanisms in heterospory. III. The plastid cycle during megasporogenesis in Isoetes.

    PubMed

    Pettitt, J M

    1976-05-01

    granules and wefts of tubular membrane. There is no evidence that the large budding organelle persists to this later stage in development. The resemblance of the plastids in the more mature megaspore to the bodies produced by evagination earlier in development suggests a common identity. The observations and interpretations lead to the proposition that the plastids in Isoetes englemanni are autonomous. This situation contrasts with the one described for another heterosporous haploid dioecious pteridophyte, Marsilea vestita, where nucleocytoplasmic interaction has been interpreted as the de novo creation of plastids and mitochondria following the elimination by autophagy of the organelles inherited at meiosis. It is suggested that an explanation to account for the 2 different mechanisms might be sought in regard to the degree of developmental success enjoyed by the individual megaspores in the 2 plants. In Isoetes all 4 megaspores of every tetrad survive and develop, while in Marsilea the mature megasporangium contains a single functional megaspore.

  12. Ribosomal scanning past the primary initiation codon as a mechanism for expression of CTL epitopes encoded in alternative reading frames

    PubMed Central

    1996-01-01

    An increasing amount of evidence has shown that epitopes restricted to MHC class I molecules and recognized by CTL need not be encoded in a primary open reading frame (ORF). Such epitopes have been demonstrated after stop codons, in alternative reading frames (RF) and within introns. We have used a series of frameshifts (FS) introduced into the Influenza A/PR/8 /34 nucleoprotein (NP) gene to confirm the previous in vitro observations of cryptic epitope expression, and show that they are sufficiently expressed to prime immune responses in vivo. This presentation is not due to sub-dominant epitopes, transcription from cryptic promoters beyond the point of the FS, or internal initiation of translation. By introducing additional mutations to the construct exhibiting the most potent presentation, we have identified initiation codon readthrough (termed scanthrough here, where the scanning ribosome bypasses the conventional initiation codon, initiating translation further downstream) as the likely mechanism of epitope production. Further mutational analysis demonstrated that, while it should operate during the expression of wild-type (WT) protein, scanthrough does not provide a major source of processing substrate in our system. These findings suggest (i) that the full array of self- and pathogen-derived epitopes available during thymic selection and infection has not been fully appreciated and (ii) that cryptic epitope expression should be considered when the specificity of a CTL response cannot be identified or in therapeutic situations when conventional CTL targets are limited, as may be the case with latent viral infections and transformed cells. Finally, initiation codon readthrough provides a plausible explanation for the presentation of exocytic proteins by MHC class I molecules. PMID:8879204

  13. Neural mechanisms underlying conflict monitoring over risky decision alternatives: evidence from ERP in a Go/Nogo task.

    PubMed

    Wang, Shuzhen; Hui, Ning; Zhou, Xinsheng; He, Kaifeng; Yu, Yuanyuan; Shuai, Jing

    2014-09-01

    This study assessed conflict monitoring during presentation of risky decision alternatives, as indexed by the Nogo-N2, Nogo-P3, N2d and P3d event-related potentials (ERP). Decision-makers were tested on a Go/Nogo gambling task in which gain/loss outcomes as well as stimulus type (Go/Nogo) were equiprobable. Frontal-central Nogo-N2 and Nogo-P3 did not significantly differ across risky decision alternatives, whereas N2d and P3d amplitudes were more sensitive to the nature of risky decision alternatives. Frontal-central N2d was moderated by the magnitude of alternatives, with N2d amplitude greater for large than small alternatives, a result that suggests a greater degree of conflict monitoring for the former. Central P3d was associated with alternative valence, such that P3d amplitude was greater for loss than gain valences, again suggestive of more conflict monitoring for the former. The N2d and P3d potentials in risky decision alternatives are discussed in terms of the functional significance of the N2/P3 complex. PMID:25164361

  14. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 4: Open recuperated and bottomed gas turbine cycles. [performance prediction and energy conversion efficiency of gas turbines in electric power plants (thermodynamic cycles)

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Grube, J. E.

    1976-01-01

    Open-cycle recuperated gas turbine plant with inlet temperatures of 1255 to 1644 K (1800 to 2500 F) and recuperators with effectiveness values of 0, 70, 80 and 90% are considered. A 1644 K (2500 F) gas turbine would have a 33.5% plant efficiency in a simple cycle, 37.6% in a recuperated cycle and 47.6% when combined with a sulfur dioxide bottomer. The distillate burning recuperated plant was calculated to produce electricity at a cost of 8.19 mills/MJ (29.5 mills/kWh). Due to their low capital cost $170 to 200 $/kW, the open cycle gas turbine plant should see duty for peaking and intermediate load duty.

  15. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 5: Combined gas-steam turbine cycles. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Foster-Pegg, R. W.; Lee, R. M.

    1976-01-01

    The energy conversion efficiency of gas-steam turbine cycles was investigated for selected combined cycle power plants. Results indicate that it is possible for combined cycle gas-steam turbine power plants to have efficiencies several point higher than conventional steam plants. Induction of low pressure steam into the steam turbine is shown to improve the plant efficiency. Post firing of the boiler of a high temperature combined cycle plant is found to increase net power but to worsen efficiency. A gas turbine pressure ratio of 12 to 1 was found to be close to optimum at all gas turbine inlet temperatures that were studied. The coal using combined cycle plant with an integrated low-Btu gasifier was calculated to have a plant efficiency of 43.6%, a capitalization of $497/kW, and a cost of electricity of 6.75 mills/MJ (24.3 mills/kwh). This combined cycle plant should be considered for base load power generation.

  16. Analyses of Alternatively Processed Genes in Ciliates Provide Insights into the Origins of Scrambled Genomes and May Provide a Mechanism for Speciation

    PubMed Central

    Gao, Feng; Roy, Scott W.

    2015-01-01

    ABSTRACT  Chromosome rearrangements occur in a variety of eukaryotic life cycles, including during the development of the somatic macronuclear genome in ciliates. Previous work on the phyllopharyngean ciliate Chilodonella uncinata revealed that macronuclear β-tubulin and protein kinase gene families share alternatively processed germ line segments nested within divergent regions. To study genome evolution in this ciliate further, we characterized two additional alternatively processed gene families from two cryptic species of the ciliate morphospecies C. uncinata: those encoding histidine acid phosphatase protein (Hap) and leishmanolysin family protein (Lei). Analyses of the macronuclear Hap and Lei sequences reveal that each gene family consists of three members in the macronucleus that are marked by identical regions nested among highly divergent regions. Investigation of the micronuclear Hap sequences revealed a complex pattern in which the three macronuclear sequences are derived either from a single micronuclear region or from a combination of this shared region recombined with additional duplicate micronuclear copies of Hap. We propose a model whereby gene scrambling evolves by gene duplication followed by partial and reciprocal degradation of the duplicate sequences. In this model, alternative processing represents an intermediate step in the evolution of scrambled genes. Finally, we speculate on the possible role of genome architecture in speciation in ciliates by describing what might happen if changes in alternatively processed loci occur in subdivided populations. PMID:25650397

  17. Parity splitting and E1/E2 branching in the alternating parity band of {sup 240}Pu from two-center octupole wave functions using supersymmetric quantum mechanics

    SciTech Connect

    Jolos, R. V.; Brentano, P. von

    2011-08-15

    An interpretation is suggested of the recently published experimental data on the alternating parity bands in {sup 240}Pu. The interpretation is based on the assumption that the main role in the description of the properties of the alternating parity bands plays the octupole mode which preserves the axial symmetry. The mathematical technique of the supersymmetric quantum mechanics is used for the realization of the model with the two-center octupole wave functions. A good description of the parity splitting and of the ratio of the dipole and quadrupole transitional moments is obtained for the first two bands.

  18. Competing Mechanisms of Gamma and Beta Oscillations in the Olfactory Bulb Based on Multimodal Inhibition of Mitral Cells Over a Respiratory Cycle123

    PubMed Central

    Courtiol, Emmanuelle; Buonviso, Nathalie

    2015-01-01

    Gamma (∼40-90 Hz) and beta (∼15-40 Hz) oscillations and their associated neuronal assemblies are key features of neuronal sensory processing. However, the mechanisms involved in either their interaction and/or the switch between these different regimes in most sensory systems remain misunderstood. Based on in vivo recordings and biophysical modeling of the mammalian olfactory bulb (OB), we propose a general scheme where OB internal dynamics can sustain two distinct dynamic states, each dominated by either a gamma or a beta regime. The occurrence of each regime depends on the excitability level of granule cells, the main OB interneurons. Using this model framework, we demonstrate how the balance between sensory and centrifugal input can control the switch between the two oscillatory dynamic states. In parallel, we experimentally observed that sensory and centrifugal inputs to the rat OB could both be modulated by the respiration of the animal (2-12 Hz) and each one phase shifted with the other. Implementing this phase shift in our model resulted in the appearance of the alternation between gamma and beta rhythms within a single respiratory cycle, as in our experimental results under urethane anesthesia. Our theoretical framework can also account for the oscillatory frequency response, depending on the odor intensity, the odor valence, and the animal sniffing strategy observed under various conditions including animal freely-moving. Importantly, the results of the present model can form a basis to understand how fast rhythms could be controlled by the slower sensory and centrifugal modulations linked to the respiration. Visual Abstract: See Abstract PMID:26665163

  19. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 9: Closed-cycle MHD. [energy conversion efficiency of electric power plants using magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Tsu, T. C.

    1976-01-01

    A closed-cycle MHD system for an electric power plant was studied. It consists of 3 interlocking loops, an external heating loop, a closed-cycle cesium seeded argon nonequilibrium ionization MHD loop, and a steam bottomer. A MHD duct maximum temperature of 2366 K (3800 F), a pressure of 0.939 MPa (9.27 atm) and a Mach number of 0.9 are found to give a topping cycle efficiency of 59.3%; however when combined with an integrated gasifier and optimistic steam bottomer the coal to bus bar efficiency drops to 45.5%. A 1978 K (3100 F) cycle has an efficiency of 55.1% and a power plant efficiency of 42.2%. The high cost of the external heating loop components results in a cost of electricity of 21.41 mills/MJ (77.07 mills/kWh) for the high temperature system and 19.0 mills/MJ (68.5 mills/kWh) for the lower temperature system. It is, therefore, thought that this cycle may be more applicable to internally heated systems such as some futuristic high temperature gas cooled reactor.

  20. Quantum mechanically derived AMBER-compatible heme parameters for various states of the cytochrome P450 catalytic cycle

    PubMed Central

    Shahrokh, Kumars; Orendt, Anita; Yost, Garold; Cheatham, Tom

    2011-01-01

    Molecular mechanics (MM) methods are computationally affordable tools for screening chemical libraries of novel compounds for sites of P450 metabolism. One challenge for MM methods has been the absence of a consistent and transferable set of parameters for the heme within the P450 active-site. Experimental data indicates that mammalian P450 enzymes vary greatly in the size, architecture, and plasticity of their active sites. Thus, obtaining x-ray based geometries for the development of accurate MM parameters for the major classes of hepatic P450 remains a daunting task. Our previous work with preliminary gas-phase quantum mechanics (QM) derived atomic partial charges, greatly improved the accuracy of docking studies of raloxifene to CYP3A4. We have therefore developed and tested a consistent set of transferable MM parameters based on gas-phase QM calculations of two model systems of the heme—a truncated (T-HM) and a full (F-HM) for four states of the P450 catalytic cycle. Our results indicate that the use of the atomic partial charges from the F-HM model further improves the accuracy of docked predictions for raloxifene to CYP3A4. Different patterns for substrate docking are also observed depending on the choice of heme model and state. Newly parameterized heme models are tested in implicit and explicitly solvated MD simulations in the absence and presence of enzyme structures, for CYP3A4, and appear to be stable on the nanosecond simulation timescale. The new force field for the various heme states may aid the community for simulations of P450 enzymes and other heme containing enzymes. PMID:21997754

  1. [Mechanisms of smooth endoplasmic reticulum aggregates creation in oocyte's cytoplasm in IVF cycles and its clinical relevance (literature review)].

    PubMed

    Kovalskaya, E V; Makarova, N P; Syrkasheva, A G; Dolgushina, N V; Kurilo, L F

    2015-01-01

    A large proportion of human oocytes received from exogenous gonadotropin-stimulated cycles have different morphological attributes, or dysmorphisms. The presence of dysmorphism can affect the fertilization rate, the embryo quality and subsequently the frequency of occurrence of implantation and pregnancy. Special attention is paid to oocytes with cytoplasmic attributes such as alteration of cytoplasmic granularity, the appearance of vacuoles, lipofuscin bodies and visible (large) aggregates of smooth endoplasmic reticulum. Endoplasmic reticulum (ER) is a type of the organelle forming an interconnected network of flattened, membrane-enclosed sacs or tubes. One of the main functions of ER in the oocyte is storage and redistribution of calcium, which provides cell activation during fertilization. Furthermore, complex of ER and mitochondria is necessary for accumulation of energy, synthesis of lipids and triglycerides, as well as synthesis of cytosolic and nuclear membranes during the early stages of cleavage. The appearance of anomalously large aggregates of ER in oocytes correlates with a low fertilization rate, low embryo quality, and pregnancy rate. The aim of the manuscript is to summarize current understanding of the mechanism of formation of such pathology of oocytes, together with special aspects of their fertilization and embryo quality.

  2. A methodology to incorporate life cycle analysis and the triple bottom line mechanism for sustainable management of industrial enterprises

    NASA Astrophysics Data System (ADS)

    Wang, Ling; Lin, Li

    2004-02-01

    Since 1970"s, the environmental protection movement has challenged industries to increase their investment in Environmentally Conscious Manufacturing (ECM) techniques and management tools. Social considerations for global citizens and their descendants also motivated the examination on the complex issues of sustainable development beyond the immediate economic impact. Consequently, industrial enterprises have started to understand sustainable development in considering the Triple Bottom Line (TBL): economic prosperity, environmental quality and social justice. For the management, however, a lack of systematic ECM methodologies hinders their effort in planning, evaluating, reporting and auditing of sustainability. To address this critical need, this research develops a framework of a sustainable management system by incorporating a Life Cycle Analysis (LCA) of industrial operations with the TBL mechanism. A TBL metric system with seven sets of indices for the TBL elements and their complex relations is identified for the comprehensive evaluation of a company"s sustainability performance. Utilities of the TBL indices are estimated to represent the views of various stakeholders, including the company, investors, employees and the society at large. Costs of these indices are also captured to reflect the company"s effort in meeting the utilities. An optimization model is formulated to maximize the economic, environmental and social benefits by the company"s effort in developing sustainable strategies. To promote environmental and social consciousness, the methodology can significantly facilitate management decisions by its capabilities of including "non-business" values and external costs that the company has not contemplated before.

  3. Flow mechanism of self-induced reversed limit-cycle wing rock for a chined forebody configuration

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Deng, Xueying; Wang, Yankui; Li, Qian

    2015-11-01

    The wing rock phenomenon reduces the maneuverability and affects the flight safety of modern advanced fighters, such as the F-35, which have chined forebodies. Understanding the flow mechanism is critical to suppressing this phenomenon. In this study, experiments were conducted to reveal the motion and flow behavior over a chined forebody configuration. The tests were performed in a wind tunnel at an angle of attack of 50∘ with a Reynolds number of 1.87 × 105. Reversed limit-cycle oscillation was discovered in the free-to-roll tests. The unstable rolling moment around zero roll angle in the static case suggests that the model tends to be driven away from zero roll angle. Thus, the model cannot maintain its equilibrium at zero roll angle during free-to-roll motion. The unstable rolling moment is generated by the wing vortex structure above the upward wing, which is induced by the forebody asymmetric vortices. During wing rock, the wing vortex structure appears above the upward wing at a large roll angle after crossing zero roll angle owing to a time lag in the forebody vortex position, which is conducive to the motion. The forebody asymmetric vortices are thus the key to induce and maintain the motion.

  4. Algal evolution in relation to atmospheric CO2: carboxylases, carbon-concentrating mechanisms and carbon oxidation cycles

    PubMed Central

    Raven, John A.; Giordano, Mario; Beardall, John; Maberly, Stephen C.

    2012-01-01

    Oxygenic photosynthesis evolved at least 2.4 Ga; all oxygenic organisms use the ribulose bisphosphate carboxylase-oxygenase (Rubisco)–photosynthetic carbon reduction cycle (PCRC) rather than one of the five other known pathways of autotrophic CO2 assimilation. The high CO2 and (initially) O2-free conditions permitted the use of a Rubisco with a high maximum specific reaction rate. As CO2 decreased and O2 increased, Rubisco oxygenase activity increased and 2-phosphoglycolate was produced, with the evolution of pathways recycling this inhibitory product to sugar phosphates. Changed atmospheric composition also selected for Rubiscos with higher CO2 affinity and CO2/O2 selectivity correlated with decreased CO2-saturated catalytic capacity and/or for CO2-concentrating mechanisms (CCMs). These changes increase the energy, nitrogen, phosphorus, iron, zinc and manganese cost of producing and operating Rubisco–PCRC, while biosphere oxygenation decreased the availability of nitrogen, phosphorus and iron. The majority of algae today have CCMs; the timing of their origins is unclear. If CCMs evolved in a low-CO2 episode followed by one or more lengthy high-CO2 episodes, CCM retention could involve a combination of environmental factors known to favour CCM retention in extant organisms that also occur in a warmer high-CO2 ocean. More investigations, including studies of genetic adaptation, are needed. PMID:22232762

  5. Benefits of clean development mechanism application on the life cycle assessment perspective: a case study in the palm oil industry.

    PubMed

    Chuen, Onn Chiu; Yusoff, Sumiani

    2012-03-01

    This study performed an assessment on the beneficial of the Clean Development Mechanism (CDM) application on waste treatment system in a local palm oil industry in Malaysia. Life cycle assessment (LCA) was conducted to assess the environmental impacts of the greenhouse gas (GHG) reduction from the CDM application. Calculations on the emission reduction used the methodology based on AM002 (Avoided Wastewater and On-site Energy Use Emissions in the Industrial Sector) Version 4 published by United Nations Framework Convention on Climate Change (UNFCC). The results from the studies showed that the introduction of CDM in the palm oil mill through conversion of the captured biogas from palm oil mill effluent (POME) treatment into power generation were able to reduce approximate 0.12 tonnes CO2 equivalent concentration (tCO2e) emission and 30 kW x hr power generation per 1 tonne of fresh fruit bunch processed. Thus, the application of CDM methodology on palm oil mill wastewater treatment was able to reduce up to 1/4 of the overall environment impact generated in palm oil mill.

  6. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 7: Metal vapor Rankine topping-steam bottoming cycles. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Deegan, P. B.

    1976-01-01

    Adding a metal vapor Rankine topper to a steam cycle was studied as a way to increase the mean temperature at which heat is added to the cycle to raise the efficiency of an electric power plant. Potassium and cesium topping fluids were considered. Pressurized fluidized bed or pressurized (with an integrated low-Btu gasifier) boilers were assumed. Included in the cycles was a pressurizing gas turbine with its associated recuperator, and a gas economizer and feedwater heater. One of the ternary systems studied shows plant efficiency of 42.3% with a plant capitalization of $66.7/kW and a cost of electricity of 8.19 mills/MJ (29.5 mills/kWh).

  7. Nuclear proliferation and civilian nuclear power. Report of the Nonproliferation Alternative Systems Assessment Program. Volume IX. Reactor and fuel cycle description

    SciTech Connect

    Not Available

    1980-06-01

    The Nonproliferation Alterntive Systems Assessment Program (NASAP) has characterized and assessed various reactor/fuel-cycle systems. Volume IX provides, in summary form, the technical descriptions of the reactor/fuel-cycle systems studied. This includes the status of the system technology, as well as a discussion of the safety, environmental, and licensing needs from a technical perspective. This information was then used in developing the research, development, and demonstration (RD and D) program, including its cost and time frame, to advance the existing technology to the level needed for commercial use. Wherever possible, the cost data are given as ranges to reflect the uncertainties in the estimates.

  8. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 6: Closed-cycle gas turbine systems. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Fentress, W. K.; Stahl, W. F.

    1976-01-01

    Both recuperated and bottomed closed cycle gas turbine systems in electric power plants were studied. All systems used a pressurizing gas turbine coupled with a pressurized furnace to heat the helium for the closed cycle gas turbine. Steam and organic vapors are used as Rankine bottoming fluids. Although plant efficiencies of over 40% are calculated for some plants, the resultant cost of electricity was found to be 8.75 mills/MJ (31.5 mills/kWh). These plants do not appear practical for coal or oil fired plants.

  9. Nuclear proliferation and civilian nuclear power. Report of the Nonproliferation Alternative Systems Assessment Program. Volume III. Resources and fuel cycle facilities

    SciTech Connect

    Not Available

    1980-06-01

    The ability of uranium supply and the rest of the nuclear fuel cycle to meet the demand for nuclear power is an important consideration in future domestic and international planning. Accordingly, the purpose of this assessment is to evaluate the adequacy of potential supply for various nuclear resources and fuel cycle facilities in the United States and in the world outside centrally planned economy areas (WOCA). Although major emphasis was placed on uranium supply and demand, material resources (thorium and heavy water) and facility resources (separative work, spent fuel storage, and reprocessing) were also considered.

  10. Alternate stresses and temperature variation as factors of influence of ultrasonic vibration on mechanical and functional properties of shape memory alloys.

    PubMed

    Belyaev, Sergey; Volkov, Alexander; Resnina, Natalia

    2014-01-01

    It is known that the main factors in a variation in the shape memory alloy properties under insonation are heating of the material and alternate stresses action. In the present work the experimental study of the mechanical behaviour and functional properties of shape memory alloy under the action of alternate stresses and varying temperature was carried out. The data obtained had demonstrated that an increase in temperature of the sample resulted in a decrease or increase in deformation stress depending on the structural state of the TiNi sample. It was shown that in the case of the alloy in the martensitic state, a decrease in stress was observed, and on the other hand, in the austenitic state an increase in stress took place. It was found that action of alternate stresses led to appearance of strain jumps on the strain-temperature curves during cooling and heating the sample through the temperature range of martensitic transformation under the constant stress. The value of the strain jumps depended on the amplitude of alternate stresses and the completeness of martensitic transformation. It was shown that the heat action of ultrasonic vibration to the mechanical behaviour of shape memory alloys was due to the non-monotonic dependence of yield stress on the temperature. The force action of ultrasonic vibration to the functional properties was caused by formation of additional oriented martensite.

  11. Seismo-mechanical modelling of megathrust earthquake cycles: influence of rate-and state-dependent friction

    NASA Astrophysics Data System (ADS)

    Herrendörfer, Robert; van Dinther, Ylona; Gerya, Taras

    2015-04-01

    Our long-term goal is to explore the cause-and-effect relationships between subduction dynamics and the megathrust earthquake potential. Therefore we are developing a 2D continuum mechanics-based numerical seismic cycle model that bridges the gap between processes on geodynamic and earthquake time scales. The initial step towards this goal was the implementation of a purely slip rate-dependent friction (Van Dinther et al. 2013) into the visco-elasto-plastic, finite difference code I2ELVIS, which uses a marker-in-cell technique. This seismo-mechanical modelling approach was validated for seismic cycle applications through a comparison against scaled analogue subduction experiments (Corbi et al. 2013). However, this comparison revealed large differences in terms of the slip behaviour in the periods between fast slip events. While diminishing interseismic creep occurs within the seismogenic zone in our numerical models, large aseismic slip was present in the analogue experiments. Here we want to overcome this mismatch by implementing the laboratory-based rate-and state dependent friction (RSF) formulation into our modelling approach. We choose the RSF formulation because, in contrast to our previous friction formulation, it takes the dependency of frictional strength on a state variable into account. The evolution of the state variable as a function of time or slip allows aseismic slip during the interseismic period within the seismogenic zone. In addition, RSF can potentially explain the transition from stick-slip behaviour to stable sliding with increasing loading velocity, which is observed in related friction experiments (Corbi et al. 2011). Here we implement the regularised version of RSF into our seismo-mechanical modelling approach by calculating and storing the analytical solution of the state evolution on each marker. In contrast to the conventional RSF formulation, we relate slip velocities to strain rates and use an invariant formulation. Thus we do not

  12. Effect of thermal cycling on the mechanical properties of Zr41Ti14Cu12.5Ni10Be22.5 alloy

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Shao, Yang; Gong, Pan; Yao, KeFu

    2012-12-01

    The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated. The metallic glassy samples are sealed into quartz tubes under high vacuum condition, and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between -196°C and 150°C. The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis, mechanical properties measurement and thermal analysis. It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles, which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.

  13. High temperature, low cycle fatigue of copper-base alloys in argon. Part 3: Zirconium-copper; thermal-mechanical strain cycling, hold-time and notch fatigue results

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1973-01-01

    The low-cycle fatigue characteristics of smooth bar and notched bar specimens (hourglass shape) of zirconium-copper, 1/2 Hard, material (R-2 Series) were evaluated at room temperature in axial strain control. Over the fatigue life range from about 300 to 3000 cycles the ratio of fatigue life for smooth bar to fatigue life for notched bar remained constant at a value of about 6.0. Some additional hold-time data for the R-2 alloy tested in argon at 538 C are reported. An analysis of the relaxation data obtained in these hold-time tests is also reported and it is shown that these data yield a fairly consistent correlation in terms of instantaneous stress rate divided by instantaneous stress. Two thermal-mechanical strain cycling tests were also performed using a cyclic frequency of 4.5 cycles per hour and a temperature cycling interval from 260 to 538 C. The fatigue life values in these tests were noticeably lower than that observed in isothermal tests at 538 C.

  14. An Alternative to Farmer Age as an Indicator of Life-Cycle Stage: The Case for a Farm Family Age Index

    ERIC Educational Resources Information Center

    Burton, Rob J. F.

    2006-01-01

    In studies of farming, the age of the principal decision-maker (PDM) has been associated with numerous farm structural and managerial features and has been widely accepted as a good indicator of the influence of life-cycle factors on decision-making. As such, it has become an important aspect of many quantitative studies of agricultural change.…

  15. Alternative Automobile Engines

    ERIC Educational Resources Information Center

    Wilson, David Gordon

    1978-01-01

    Requirements for cleaner and more efficient engines have stimulated a search for alternatives to the conventional spark-ignition engine. So far, the defects of the alternative engines are clearer than the virtues. The following engines are compared: spark ignition, diesel, vapor-cycle, Stirling, and gas turbine. (Author/MA)

  16. [Mechanical infertility in the female population of the Kielce province. IV. Evaluation of hypophyseal gonadotropin levels during the [Mechanical infertility in the female population of the Kielce province. IV. Evaluation of hypophyseal gonadotropin levels during the menstrual cycle].

    PubMed

    Szczurowicz, A; Witczak, A; Szczurowicz, A; Witek, K; Ziółkowski, T; Maciejewski, K

    1993-10-01

    The paper describes results of the RIA of the hypophyseal gonadotropins estimated in the menstrual cycle in the group of women with mechanical sterility in confrontation with the group of fertile women. Significantly higher mean concentration of FSH in follicular and luteal phase and higher concentration of LH after ovulation in the group of sterile women were found. There was no LH peak and mean concentration in 14th day of menstrual cycle was significantly lower in the group of women with mechanical sterility. Mean PRL concentration was higher but within the bounds of standard in sterile women.

  17. Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling.

    PubMed

    Amaral, Marina; Rippe, Marilia Pivetta; Bergoli, Cesar Dalmolin; Monaco, Carlo; Valandro, Luiz Felipe

    2011-01-01

    This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results.

  18. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 8: Open-cycle MHD. [energy conversion efficiency and design analysis of electric power plants employing magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Hoover, D. Q.

    1976-01-01

    Electric power plant costs and efficiencies are presented for three basic open-cycle MHD systems: (1) direct coal fired system, (2) a system with a separately fired air heater, and (3) a system burning low-Btu gas from an integrated gasifier. Power plant designs were developed corresponding to the basic cases with variation of major parameters for which major system components were sized and costed. Flow diagrams describing each design are presented. A discussion of the limitations of each design is made within the framework of the assumptions made.

  19. On the possible mechanism of the first ground level enhancement in cosmic ray intensity of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Firoz, Kazi A.; Gan, W. Q.; Li, Y. P.; Rodriguez-Pacheco, J.

    2014-03-01

    We have carried out this work to comprehend the possible mechanisms of the first ground level enhancement (GLE71 17 May 2012 01:50 UT) in cosmic ray intensity of the solar cycle 24. For this, the cosmic ray intensities registered by neutron monitors at several sites have been analyzed and studied with concurrent solar flares of different energy channels. To assess empirically whether the GLE might have been caused by the energy released from solar flare or CME-driven shock, we identify the possible time line in terms of the lowest spectral index determined from proton fluxes. If the GLE is caused by the energy released from particle acceleration in solar flare, the intensive phase of the flare representing the extreme emission should exist within/around the possible time line. In this respect, it is observed that the possible time line lies within the prominent phase of CME-driven shock. For better understanding, we have checked the possible relativistic energy with respect to solar flare as well as CME-driven shock. As witnessed, if the extreme emission phase of the flare is considered as the reason for the causation of GLE peak, the flare components procured insufficient amount of energy (≤˜0.085 GeV) to produce a GLE. If the extreme emission phase of the flare is also considered as the dominator along GLE onset, the possible energy procurement (≤˜0.414 GeV) is still not adequate to produce a GLE. In contrast, the CME-driven shock is capable of procuring enough possible relativistic energy (≥˜1.21 GeV) that is sufficient amount of the energy for a GLE production. Any amount of the energy (<0.414 GeV) released from preceding flare components is supposed to have been contributed to the shock process. Thus, it is assumed that the GLE71 was possibly caused by the energy released from the shock acceleration, which might have been boosted by the energy emanated from preceding flare.

  20. Developmental plasticity and the evolution of animal complex life cycles

    PubMed Central

    Minelli, Alessandro; Fusco, Giuseppe

    2010-01-01

    Metazoan life cycles can be complex in different ways. A number of diverse phenotypes and reproductive events can sequentially occur along the cycle, and at certain stages a variety of developmental and reproductive options can be available to the animal, the choice among which depends on a combination of organismal and environmental conditions. We hypothesize that a diversity of phenotypes arranged in developmental sequence throughout an animal's life cycle may have evolved by genetic assimilation of alternative phenotypes originally triggered by environmental cues. This is supported by similarities between the developmental mechanisms mediating phenotype change and alternative phenotype determination during ontogeny and the common ecological condition that favour both forms of phenotypic variation. The comparison of transcription profiles from different developmental stages throughout a complex life cycle with those from alternative phenotypes in closely related polyphenic animals is expected to offer critical evidence upon which to evaluate our hypothesis. PMID:20083638

  1. Repeated freeze-thaw cycles reduce the survival rate of osteocytes in bone-tendon constructs without affecting the mechanical properties of tendons.

    PubMed

    Suto, Kaori; Urabe, Ken; Naruse, Kouji; Uchida, Kentaro; Matsuura, Terumasa; Mikuni-Takagaki, Yuko; Suto, Mitsutoshi; Nemoto, Noriko; Kamiya, Kentaro; Itoman, Moritoshi

    2012-03-01

    Frozen bone-patellar tendon bone allografts are useful in anterior cruciate ligament reconstruction as the freezing procedure kills tissue cells, thereby reducing immunogenicity of the grafts. However, a small portion of cells in human femoral heads treated by standard bone-bank freezing procedures survive, thus limiting the effectiveness of allografts. Here, we characterized the survival rates and mechanisms of cells isolated from rat bones and tendons that were subjected to freeze-thaw treatments, and evaluated the influence of these treatments on the mechanical properties of tendons. After a single freeze-thaw cycle, most cells isolated from frozen bone appeared morphologically as osteocytes and expressed both osteoblast- and osteocyte-related genes. Transmission electron microscopic observation of frozen cells using freeze-substitution revealed that a small number of osteocytes maintained large nuclei with intact double membranes, indicating that these osteocytes in bone matrix were resistant to ice crystal formation. We found that tendon cells were completely killed by a single freeze-thaw cycle, whereas bone cells exhibited a relatively high survival rate, although survival was significantly reduced after three freeze-thaw cycles. In patella tendons, the ultimate stress, Young's modulus, and strain at failure showed no significant differences between untreated tendons and those subjected to five freeze-thaw cycles. In conclusion, we identified that cells surviving after freeze-thaw treatment of rat bones were predominantly osteocytes. We propose that repeated freeze-thaw cycles could be applied for processing bone-tendon constructs prior to grafting as the treatment did not affect the mechanical property of tendons and drastically reduced surviving osteocytes, thereby potentially decreasing allograft immunogenecity.

  2. Segmental Duplications Arise from Pol32-Dependent Repair of Broken Forks through Two Alternative Replication-Based Mechanisms

    PubMed Central

    Dujon, Bernard; Fischer, Gilles

    2008-01-01

    The propensity of segmental duplications (SDs) to promote genomic instability is of increasing interest since their involvement in numerous human genomic diseases and cancers was revealed. However, the mechanism(s) responsible for their appearance remain mostly speculative. Here, we show that in budding yeast, replication accidents, which are most likely transformed into broken forks, play a causal role in the formation of SDs. The Pol32 subunit of the major replicative polymerase Polδ is required for all SD formation, demonstrating that SDs result from untimely DNA synthesis rather than from unequal crossing-over. Although Pol32 is known to be required for classical (Rad52-dependant) break-induced replication, only half of the SDs can be attributed to this mechanism. The remaining SDs are generated through a Rad52-independent mechanism of template switching between microsatellites or microhomologous sequences. This new mechanism, named microhomology/microsatellite-induced replication (MMIR), differs from all known DNA double-strand break repair pathways, as MMIR-mediated duplications still occur in the combined absence of homologous recombination, microhomology-mediated, and nonhomologous end joining machineries. The interplay between these two replication-based pathways explains important features of higher eukaryotic genomes, such as the strong, but not strict, association between SDs and transposable elements, as well as the frequent formation of oncogenic fusion genes generating protein innovations at SD junctions. PMID:18773114

  3. Study of the deterioration mechanism of LiCoO2/graphite cells in charge/discharge cycles using the discharge curve analysis

    NASA Astrophysics Data System (ADS)

    Honkura, Kohei; Horiba, Tatsuo

    2014-10-01

    The differential discharge curve analysis that separates the discharge curve of battery cells into those of the positive and negative electrodes is useful for investigating deterioration mechanisms. We applied it to LiCoO2/graphite cells and investigated the capacity fading mechanisms during charge/discharge cycles. In the initial state, the discharge curves of the cells were reconstructed very well by the discharge curves of the positive and negative electrodes measured in advance. The discharge curve analysis revealed that the initial cell capacities were controlled by the negative electrodes. On the other hand, the capacity of the positive electrode decreased faster than that of the negative electrode during the course of the cycle test. With repeated charge/discharge cycles, the positive electrodes came to control the cell capacities. After that, deep charge/discharge cycles of the positive electrode accelerated the loss of capacity and the increase of the internal resistance. Furthermore, the rapid increase of the internal resistance lowered the accuracy of the discharge curve analysis. Although the discharge curve analysis was still applicable to the cells that were controlled by the positive electrodes, there were some discrepancies around the endpoints of the discharge curves.

  4. Cell output, cell cycle duration and neuronal specification: a model of integrated mechanisms of the neocortical proliferative process

    NASA Technical Reports Server (NTRS)

    Caviness, V. S. Jr; Goto, T.; Tarui, T.; Takahashi, T.; Bhide, P. G.; Nowakowski, R. S.

    2003-01-01

    The neurons of the neocortex are generated over a 6 day neuronogenetic interval that comprises 11 cell cycles. During these 11 cell cycles, the length of cell cycle increases and the proportion of cells that exits (Q) versus re-enters (P) the cell cycle changes systematically. At the same time, the fate of the neurons produced at each of the 11 cell cycles appears to be specified at least in terms of their laminar destination. As a first step towards determining the causal interrelationships of the proliferative process with the process of laminar specification, we present a two-pronged approach. This consists of (i) a mathematical model that integrates the output of the proliferative process with the laminar fate of the output and predicts the effects of induced changes in Q and P during the neuronogenetic interval on the developing and mature cortex and (ii) an experimental system that allows the manipulation of Q and P in vivo. Here we show that the predictions of the model and the results of the experiments agree. The results indicate that events affecting the output of the proliferative population affect both the number of neurons produced and their specification with regard to their laminar fate.

  5. Environmental decision-making using life cycle impact assessment and stochastic multiattribute decision analysis: a case study on alternative transportation fuels.

    PubMed

    Rogers, Kristin; Seager, Thomas P

    2009-03-15

    Life cycle impact assessment (LCIA) involves weighing trade-offs between multiple and incommensurate criteria. Current state-of-the-art LCIA tools typically compute an overall environmental score using a linear-weighted aggregation of characterized inventory data that has been normalized relative to total industry, regional, or national emissions. However, current normalization practices risk masking impacts that may be significant within the context of the decision, albeit small relative to the reference data (e.g., total U.S. emissions). Additionally, uncertainty associated with quantification of weights is generally very high. Partly for these reasons, many LCA studies truncate impact assessment at the inventory characterization step, rather than completing normalization and weighting steps. This paper describes a novel approach called stochastic multiattribute life cycle impact assessment (SMA-LCIA) that combines an outranking approach to normalization with stochastic exploration of weight spaces-avoiding some of the drawbacks of current LCIA methods. To illustrate the new approach, SMA-LCIA is compared with a typical LCIA method for crop-based, fossil-based, and electric fuels using the Greenhouse gas Regulated Emissions and Energy Use in Transportation (GREET) model for inventory data and the Tool for the Reduction and Assessment of Chemical and other Environmental Impacts (TRACI) model for data characterization. In contrast to the typical LCIA case, in which results are dominated by fossil fuel depletion and global warming considerations regardless of criteria weights, the SMA-LCIA approach results in a rank ordering that is more sensitive to decisionmaker preferences. The principal advantage of the SMA-LCIA method is the ability to facilitate exploration and construction of context-specific criteria preferences by simultaneously representing multiple weights spaces and the sensitivity of the rank ordering to uncertain stakeholder values. PMID:19368162

  6. Impact of Cooling Rate-Induced Recrystallization on High G Mechanical Shock and Thermal Cycling in Sn-Ag-Cu Solder Interconnects

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Kyu; Bieler, Thomas R.; Kim, Choong-Un

    2016-01-01

    The mechanical stability and thermo-mechanical fatigue performance of solder joints with low silver content Sn-1.0Ag-0.5Cu (wt.%) (SAC105) alloy based on different cooling rates are investigated in high G level shock environment and thermal cycling conditions. The cooling rate-controlled samples ranging from 1°C/min to 75°C/min cooling rate, not only show differences in microstructure, where a fine poly-granular microstructure develops in the case of fast cooling versus normal cooling, but also show various shock performances based on the microstructure changes. The fast cooling rate improves the high G shock performance by over 90% compared to the normal cooled SAC105 alloy air-cooling environment commonly used after assembly reflow. The microstructure effect on thermal cycling performance is also discussed, which is analyzed based on the Sn grain orientation, interconnect stability, and solder joint bulk microstructure.

  7. Ambient particulate matter induces IL-8 expression through an alternative NF-kB mechanism in human airway epithelial cells

    EPA Science Inventory

    BACKGROUND: Exposure to ambient air particulate matter (PM) has been shown to increase rates of cardio-pulmonary morbidity and mortality, but the underlying mechanisms are still not well understood. OBJECTIVE: To examine signaling events involved in the expression of the inflamma...

  8. Mechanical Stimulation (Pulsed Electromagnetic Fields "PEMF" and Extracorporeal Shock Wave Therapy "ESWT") and Tendon Regeneration: A Possible Alternative.

    PubMed

    Rosso, Federica; Bonasia, Davide E; Marmotti, Antonio; Cottino, Umberto; Rossi, Roberto

    2015-01-01

    The pathogenesis of tendon degeneration and tendinopathy is still partially unclear. However, an active role of metalloproteinases (MMP), growth factors, such as vascular endothelial growth factor (VEGF) and a crucial role of inflammatory elements and cytokines was demonstrated. Mechanical stimulation may play a role in regulation of inflammation. In vitro studies demonstrated that both pulsed electromagnetic fields (PEMF) and extracorporeal shock wave therapy (ESWT) increased the expression of pro-inflammatory cytokine such as interleukin (IL-6 and IL-10). Moreover, ESWT increases the expression of growth factors, such as transforming growth factor β(TGF-β), (VEGF), and insulin-like growth factor 1 (IGF1), as well as the synthesis of collagen I fibers. These pre-clinical results, in association with several clinical studies, suggest a potential effectiveness of ESWT for tendinopathy treatment. Recently PEMF gained popularity as adjuvant for fracture healing and bone regeneration. Similarly to ESWT, the mechanical stimulation obtained using PEMFs may play a role for treatment of tendinopathy and for tendon regeneration, increasing in vitro TGF-β production, as well as scleraxis and collagen I gene expression. In this manuscript the rational of mechanical stimulations and the clinical studies on the efficacy of extracorporeal shock wave (ESW) and PEMF will be discussed. However, no clear evidence of a clinical value of ESW and PEMF has been found in literature with regards to the treatment of tendinopathy in human, so further clinical trials are needed to confirm the promising hypotheses concerning the effectiveness of ESWT and PEMF mechanical stimulation.

  9. Alternative security

    SciTech Connect

    Weston, B.H. )

    1990-01-01

    This book contains the following chapters: The Military and Alternative Security: New Missions for Stable Conventional Security; Technology and Alternative Security: A Cherished Myth Expires; Law and Alternative Security: Toward a Just World Peace; Politics and Alternative Security: Toward a More Democratic, Therefore More Peaceful, World; Economics and Alternative Security: Toward a Peacekeeping International Economy; Psychology and Alternative Security: Needs, Perceptions, and Misperceptions; Religion and Alternative Security: A Prophetic Vision; and Toward Post-Nuclear Global Security: An Overview.

  10. Dynamical Localization of DivL and PleC in the Asymmetric Division Cycle of Caulobacter crescentus: A Theoretical Investigation of Alternative Models.

    PubMed

    Subramanian, Kartik; Paul, Mark R; Tyson, John J

    2015-07-01

    Cell-fate asymmetry in the predivisional cell of Caulobacter crescentus requires that the regulatory protein DivL localizes to the new pole of the cell where it up-regulates CckA kinase, resulting in a gradient of CtrA~P across the cell. In the preceding stage of the cell cycle (the "stalked" cell), DivL is localized uniformly along the cell membrane and maintained in an inactive form by DivK~P. It is unclear how DivL overcomes inhibition by DivK~P in the predivisional cell simply by changing its location to the new pole. It has been suggested that co-localization of DivL with PleC phosphatase at the new pole is essential to DivL's activity there. However, there are contrasting views on whether the bifunctional enzyme, PleC, acts as a kinase or phosphatase at the new pole. To explore these ambiguities, we formulated a mathematical model of the spatiotemporal distributions of DivL, PleC and associated proteins (DivJ, DivK, CckA, and CtrA) during the asymmetric division cycle of a Caulobacter cell. By varying localization profiles of DivL and PleC in our model, we show how the physiologically observed spatial distributions of these proteins are essential for the transition from a stalked cell to a predivisional cell. Our simulations suggest that PleC is a kinase in predivisional cells, and that, by sequestering DivK~P, the kinase form of PleC enables DivL to be reactivated at the new pole. Hence, co-localization of PleC kinase and DivL is essential to establishing cellular asymmetry. Our simulations reproduce the experimentally observed spatial distribution and phosphorylation status of CtrA in wild-type and mutant cells. Based on the model, we explore novel combinations of mutant alleles, making predictions that can be tested experimentally.

  11. Identification of novel markers of alternative activation and potential endogenous PPARγ ligand production mechanisms in human IL-4 stimulated differentiating macrophages.

    PubMed

    Czimmerer, Zsolt; Varga, Tamas; Poliska, Szilard; Nemet, Istvan; Szanto, Attila; Nagy, Laszlo

    2012-12-01

    We analyzed global gene expression profiles of IL-4 induced alternatively activated as well as IFNγ+TNFα stimulated classically activated human monocyte derived macrophages and identified novel IL-4 regulated alternative activation marker genes including MS4A4A, SLA, CD180, and ENPP2. Transcription factor prediction analysis of IL-4 regulated genes suggested that the regulated genes are involved in a complex regulation of lipid metabolism, defense against cell metabolism derived reactive oxygen species, and basal expression of inflammation linked genes. Both an in silico transcription activation prediction as well as experimental data suggested the presence of alternative macrophage activation specific endogenous PPARγ ligand producing mechanisms. We found the induction of three enzymes whose activity can potentially generate endogenous PPARγ ligands in an IL-4 dependent manner. These are MAOA, ENPP2, and ALOX15 producing 5-methoxy-indole acetate, lysophosphatidic acid (LPA) and 13-hydroxyoctadienoic acid (13-HODE), and/or 15-hydroxyeicosatetraenoic acid (15-HETE), respectively. Our data suggest that global gene expression profiling, combined with computational transcription activity prediction, can lead to identification of transcriptional networks that underpin cellular subtype specification.

  12. A Proposed Alternative Mechanism of Action for Transmyocardial Revascularization Prefaced by a Review of the Accepted Explanations

    PubMed Central

    Cardarelli, Marcelo

    2006-01-01

    Laser transmyocardial revascularization, a procedure originally intended to simulate the perfusion mechanism of the reptilian heart, has evolved into an effective but poorly understood treatment for angina when traditional revascularization is not an option. Herein, we review the explanations that have been proposed over the years and suggest a new one. We hypothesize that the long-term mechanism of action of transmyocardial revascularization is the redistribution of stresses on the ventricular wall through the creation of fibrous transmyocardial scars, which penetrate the various layers of muscle that surround the left ventricular cavity. The stress redistribution of a load in an otherwise unchanged ventricular wall reduces the wall stress per unit of wall volume, which in turn decreases the workload for the hyperkinetic compensating areas. This reduces both oxygen demand and local metabolite production, lowering the level of angina. PMID:17215963

  13. Energy balances in the production and end use of alcohols derived from biomass. A fuels-specific comparative analysis of alternate ethanol production cycles

    SciTech Connect

    Not Available

    1980-10-01

    Considerable public interest and debate have been focused on the so-called energy balance issue involved in the conversion of biomass materials into ethanol for fuel use. This report addresses questions of net gains in premium fuels that can be derived from the production and use of ethanol from biomass, and shows that for the US alcohol fuel program, energy balance need not be a concern. Three categories of fuel gain are discussed in the report: (1) Net petroleum gain; (2) Net premium fuel gain (petroleum and natural gas); and (3) Net energy gain (for all fuels). In this study the investment of energy (in the form of premium fuels) in alcohol production includes all investment from cultivating, harvesting, or gathering the feedstock and raw materials, through conversion of the feedstock to alcohol, to the delivery to the end-user. To determine the fuel gains in ethanol production, six cases, encompassing three feedstocks, five process fuels, and three process variations, have been examined. For each case, two end-uses (automotive fuel use and replacement of petrochemical feedstocks) were scrutinized. The end-uses were further divided into three variations in fuel economy and two different routes for production of ethanol from petrochemicals. Energy requirements calculated for the six process cycles accounted for fuels used directly and indirectly in all stages of alcohol production, from agriculture through distribution of product to the end-user. Energy credits were computed for byproducts according to the most appropriate current use.

  14. Disposal of post-consumer polyethylene terephthalate (PET) bottles: comparison of five disposal alternatives in the small island state of Mauritius using a life cycle assessment tool.

    PubMed

    Foolmaun, Rajendra Kumar; Ramjeeawon, Toolseeram

    2012-01-01

    Used polyethylene terephthalate bottles (PET) dumped indiscriminately onto bare lands and water bodies constitute an eyesore. This problem is viewed as a serious impediment to the flourishing tourism industry in Mauritius. Currently, over 100 million PET bottles are generated annually and the only fully operational disposal route is through the sole sanitary landfill. There is no formal segregation of waste and therefore used PET bottles are disposed of commingled with domestic waste. Despite a satisfactory waste collection system, a considerable amount of used PET bottles unfortunately end up in water bodies and on bare lands. An appreciable amount of PET bottles is now being collected separately for flake production prior to export to South Africa. This paper investigated the environmental impact of five waste management scenarios (100% landfill; 100% incineration with energy recovery; 50% incineration and 50% landfill; 34% flake production and 66% landfill; 100% flake production) for used PET bottles in Mauritius. Comparison of the five scenarios was based on the life cycle assessment (LCA) methodology described in ISO 14040 and ISO 14044. SimaPro 7.1 software was used to analyse the data. Comparison of the five scenarios showed that the highest environmental impacts occurred when 100% of used PET bottles were sent to the landfill. The comparison also indicated that there were least impacts on the environment when all used PET bottles were incinerated with energy recovery. PMID:22629630

  15. Thermal-Fatigue Crack-Growth Characteristics and Mechanical Strain Cycling Behavior of A-286 Discaloy, and 16-25-6 Austenitic Steels

    NASA Technical Reports Server (NTRS)

    Smith, Robert W.; Smith, Gordon T.

    1960-01-01

    Thermal-fatigue crack-growth characteristics of notched- and unnotched-disk specimens of A-286, Discaloy, hot-cold worked 16-25-6, and overaged 16-25-6 were experimentally studied. Separately controlled variables were total strain range (0.0043 to 0.0079 in./in.), maximum cycle temperature (1300 and 1100 F), and hold time at maximum temperature (O and 5 min). A limited number of mechanical, push-pull, constant-strain cycle tests at room temperature were made using notched and un-notched bars of the same materials. In these tests the number of cycles to failure as well as the variation of load change with accumulated cycles was measured, and the effects of mean stress were observed. Constant-strain-range mechanical-fatigue tests at room temperature revealed notched-bar fatigue life to be strongly influenced by mean stress. For a specific strain range, the longest fatigue life was always found to be associated with the least-tensile (or most compressive) mean stress. By defining thermal-fatigue life as the number of cycles required to produce a crack area of 6000 square mils, the relative thermal-fatigue resistances of the test materials were established. Notched-disk specimens of A-286 and Discaloy steels exhibited longer fatigue lives than either hot-cold worked or overaged 16-25-6. On the other hand, unnotched-disk specimens of Discaloy and hot-cold worked 16-25-6 had longer lives than A-286 and overaged 16-25-6. Separation of the crack-growth data into microstage and macrostage periods revealed that the macrostage period accounted for the greatest part of the difference among materials when tested in the notched configuration, while the microstage was largely responsible for the differences encountered in unnotched disks.

  16. More about neutron Majorana mass from exotic instantons: An alternative mechanism in low-scale string theory

    NASA Astrophysics Data System (ADS)

    Addazi, Andrea

    2016-06-01

    We discuss an alternative for baryon-violating six quarks transition in the context of low scale string theory. In particular, with MS = 10-103 TeV, such a transition can be mediated by two color-triplets through a quartic coupling with down-quarks, generated by exotic instantons, in a calculable and controllable way. We show how flavor-changing neutral currents (FCNCs) limits on color-triplet mass are well compatible with n ‑n¯ oscillation ones. If an n ‑n¯ transition was found, this would be an indirect hint for our model. This would strongly motivate searches for direct channels in proton-proton colliders. In fact, our model can be directly tested in an experimentally challenging 100-1000 TeV proton-proton collider, searching for our desired color-triplet states and an evidence for exotic instantons resonances, in addition to stringy Regge resonances, anomalous Z‧-bosons and gauged megaxion. In particular, our scenario can be related to the 750 GeV diphoton hint identifying it with the gauged megaxion dual to the B-field. On the other hand, this scenario is compatible with TeV-ish color triplets visible at large hadron collider (LHC) and with 1-10 TeV string scale, i.e. stringy resonances at LHC.

  17. More about neutron Majorana mass from exotic instantons: An alternative mechanism in low-scale string theory

    NASA Astrophysics Data System (ADS)

    Addazi, Andrea

    2016-06-01

    We discuss an alternative for baryon-violating six quarks transition in the context of low scale string theory. In particular, with MS = 10-103 TeV, such a transition can be mediated by two color-triplets through a quartic coupling with down-quarks, generated by exotic instantons, in a calculable and controllable way. We show how flavor-changing neutral currents (FCNCs) limits on color-triplet mass are well compatible with n -n¯ oscillation ones. If an n -n¯ transition was found, this would be an indirect hint for our model. This would strongly motivate searches for direct channels in proton-proton colliders. In fact, our model can be directly tested in an experimentally challenging 100-1000 TeV proton-proton collider, searching for our desired color-triplet states and an evidence for exotic instantons resonances, in addition to stringy Regge resonances, anomalous Z‧-bosons and gauged megaxion. In particular, our scenario can be related to the 750 GeV diphoton hint identifying it with the gauged megaxion dual to the B-field. On the other hand, this scenario is compatible with TeV-ish color triplets visible at large hadron collider (LHC) and with 1-10 TeV string scale, i.e. stringy resonances at LHC.

  18. Simulation of life-cycle efficiency of lamb and wool production for genetic levels of component traits and alternative management options.

    PubMed

    Wang, C T; Dickerson, G E

    1991-11-01

    A deterministic computer model was used to predict effects of genetic improvements in performance and of management options on life-cycle flock TDN input per unit of empty body weight (EBW) or carcass lean (CLN) equivalent value of market lamb, cull ewe, and wool output from a pure breeding system of sheep production for sheep fed to maintain normal weight. Relative values per kilogram for market lambs, cull ewes, and clean wool were 1 to .33 to 2.04 in lamb empty body equivalent, but 1 to .33 to 1 in lamb carcass lean equivalent. A 10% increase in lamb viability improved TDN/EBW or CLN by -15 to -20% for high to low lambing rates. Corresponding smaller gains were -7 to -11% for fertility, -3 to -13% for lambing rate, -1 to -3% for wool growth rate, -1 to -5% for milk production without creep feeding, -2 to -1% for mature size to about 70 kg, and -.6 to -.9% for precocity of fertility. Increasing leanness 10% improved TDN/CLN by -3 to -1% but increased TDN/EBW 3% because of higher maintenance requirements of leaner sheep. Higher protein requirements for increased lambing rate, milk production or leanness, or greater increases in non-feed than in feed costs, would mean only slightly less reduction of TDN/output than shown. Creep feeding was beneficial only for prolific, low-milking stock. Flushing reduced adverse effects of restricted feeding. Different values for wool vs meat or for costs of feed vs non-feed inputs would change results. These estimates for relative economic importance of traits apply to derivation of optimum criteria for selection among breeds or crosses, or within-breeds used in rotation crossbreeding, but would differ for specialized terminal-sire or maternal breed roles. PMID:1752808

  19. 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.

  20. Theoretical study of mesoscopic stochastic mechanism and effects of finite size on cell cycle of fission yeast

    NASA Astrophysics Data System (ADS)

    Yi, Ming; Jia, Ya; Tang, Jun; Zhan, Xuan; Yang, Lijian; Liu, Quan

    2008-01-01

    Based on a deterministic cell cycle model, the mesoscopic stochastic differential equations are theoretically derived from the biochemical reactions. The effects of the finite cell size on the cell cycle regulation in the wild type and wee1-cdc25Δ double mutant type are numerically studied by virtue of the chemical Langevin equations. (i) When the system is driven only by the internal noise, our numerical results are in qualitative agreement well with some experimental observations and data. (ii) A parameter, which is sensitive to two resettings of M-phase promoting factor to G2, is treated as a stochastic variable, and the system driven only by the external noise for double mutant type is investigated. (iii) When the system is driven by both the internal and external noise, a simple discussion about the combined effect for double mutant type is given. Our results imply some experimental results would be explained by introducing the appropriate internal or external noise into the cell cycle system.

  1. Cell cycle arrest and mechanism of apoptosis induction in H400 oral cancer cells in response to Damnacanthal and Nordamnacanthal isolated from Morinda citrifolia.

    PubMed

    Shaghayegh, Gohar; Alabsi, Aied M; Ali-Saeed, Rola; Ali, Abdul Manaf; Vincent-Chong, Vui King; Zain, Rosnah Binti

    2016-10-01

    Oral cancer is the eleventh most prevalent cancer worldwide. The most prevalent oral cancer is oral squamous cell carcinoma (OSCC). Damnacanthal (DAM) and nordamnacanthal (NDAM), the anthraquinone compounds, are isolated from the root of Morinda citrifolia L. (Noni), which has been used for the treatment of several chronic diseases including cancer. The objectives of this study were to evaluate the cytotoxicity, cell death mode, cell cycle, and the molecular mechanism of apoptosis induced by DAM and NDAM on OSCC. The cytotoxic effects of these compounds against OSCC cell lines were determined by MTT assay. The cell death mode was analysed by DNA laddering and FITC-annexin V/PI flow cytometric assays. In addition, the mechanism of apoptosis induced by DAM and NDAM was detected using mitochondrial membrane potential, Cytochrome c, and caspases assays. Finally, the effect of DAM and NDAM on cell cycle phase distribution of OSCC cells was detected by flow cytometry. In the present study, DAM and NDAM showed cytotoxicity towards OSCC cell lines and the maximum growth inhibition for both compounds was observed in H400 cells with IC50 value of 1.9 and 6.8 μg/ml, respectively, after 72 h treatment. The results also demonstrated the inhibition of H400 OSCC cells proliferation, internucleosomal cleavage of DNA, activation of intrinsic apoptosis pathway, and cell cycle arrest caused by DAM and NDAM. Therefore, these findings suggest that DAM and NDAM can be potentially used as antitumor agents for oral cancer therapy.

  2. Dependence of the mechanical behavior of alloys on their electron work function—An alternative parameter for materials design

    SciTech Connect

    Lu, Hao; Hua, Guomin; Li, Dongyang

    2013-12-23

    In this article, we demonstrate that the electron work function (EWF) as an intrinsic parameter can provide information or clues in a simple or straightforward way for material design, modification, and development. A higher work function of a material represents a more stable electronic state, which consequently generates a higher resistance to any attempt of changing the electronic state and other corresponding states, e.g., changes in structure or microstructure caused by mechanical and electrochemical actions. Using Cu-Ni alloy as an example, we demonstrate the correlation between the EWF and Young's modulus of the material as well as its hardness. The properties of a material can be modified using elements with appropriate work functions. This is also applicable for tailoring inter-phase boundaries or interfaces.

  3. Alternative Interpretation of Low-Energy Nuclear Reaction Processes with Deuterated Metals Based on the Bose-Einstein Condensation Mechanism

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Passell, Thomas O.

    2006-02-01

    Recently, a generalization of the Bose-Einstein condensation (BEC) mechanism has been made to a ground-state mixture of two different species of positively charged bosons in harmonic traps. The theory has been used to describe (D + Li) reactions in the low energy nuclear reaction (LENR) processes in condensed matter and predicts that the (D + Li) reaction rates can be larger than (D + D) reaction rates by as much as a factor of ~50, implying that (D + Li) reactions may be occuring in addition to the (D + D) reactions. A survey of the existing data from LENR experiments is carried out to check the validity of the theoretical prediction. We conclude that there is compelling experimental evidence which support the theoretical prediction. New experimental tests of the theoretical prediction are suggested.

  4. An alternative mechanism for the catalysis of peptide bond formation by L/F transferase: substrate binding and orientation.

    PubMed

    Fung, Angela W; Ebhardt, H Alexander; Abeysundara, Heshani; Moore, Jack; Xu, Zhizhong; Fahlman, Richard P

    2011-06-17

    Eubacterial leucyl/phenylalanyl tRNA protein transferase (L/F transferase) catalyzes the transfer of a leucine or a phenylalanine from an aminoacyl-tRNA to the N-terminus of a protein substrate. This N-terminal addition of an amino acid is analogous to that of peptide synthesis by ribosomes. A previously proposed catalytic mechanism for Escherichia coli L/F transferase identified the conserved aspartate 186 (D186) and glutamine 188 (Q188) as key catalytic residues. We have reassessed the role of D186 and Q188 by investigating the enzymatic reactions and kinetics of enzymes possessing mutations to these active-site residues. Additionally three other amino acids proposed to be involved in aminoacyl-tRNA substrate binding are investigated for comparison. By quantitatively measuring product formation using a quantitative matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based assay, our results clearly demonstrate that, despite significant reduction in enzymatic activity as a result of different point mutations introduced into the active site of L/F transferase, the formation of product is still observed upon extended incubations. Our kinetic data and existing X-ray crystal structures result in a proposal that the critical roles of D186 and Q188, like the other amino acids in the active site, are for substrate binding and orientation and do not directly participate in the chemistry of peptide bond formation. Overall, we propose that L/F transferase does not directly participate in the chemistry of peptide bond formation but catalyzes the reaction by binding and orientating the substrates for reaction in an analogous mechanism that has been described for ribosomes.

  5. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  6. The two active sites in human branched-chain alpha-keto acid dehydrogenase operate independently without an obligatory alternating-site mechanism.

    PubMed

    Li, Jun; Machius, Mischa; Chuang, Jacinta L; Wynn, R Max; Chuang, David T

    2007-04-20

    A long standing controversy is whether an alternating activesite mechanism occurs during catalysis in thiamine diphosphate (ThDP)-dependent enzymes. We address this question by investigating the ThDP-dependent decarboxylase/dehydrogenase (E1b) component of the mitochondrial branched-chain alpha-keto acid dehydrogenase complex (BCKDC). Our crystal structure reveals that conformations of the two active sites in the human E1b heterotetramer harboring the reaction intermediate are identical. Acidic residues in the core of the E1b heterotetramer, which align with the proton-wire residues proposed to participate in active-site communication in the related pyruvate dehydrogenase from Bacillus stearothermophilus, are mutated. Enzyme kinetic data show that, except in a few cases because of protein misfolding, these alterations are largely without effect on overall activity of BCKDC, ruling out the requirement of a proton-relay mechanism in E1b. BCKDC overall activity is nullified at 50% phosphorylation of E1b, but it is restored to nearly half of the pre-phosphorylation level after dissociation and reconstitution of BCKDC with the same phosphorylated E1b. The results suggest that the abolition of overall activity likely results from the specific geometry of the half-phosphorylated E1b in the BCKDC assembly and not due to a disruption of the alternating active-site mechanism. Finally, we show that a mutant E1b containing only one functional active site exhibits half of the wild-type BCKDC activity, which directly argues against the obligatory communication between active sites. The above results provide evidence that the two active sites in the E1b heterotetramer operate independently during the ThDP-dependent decarboxylation reaction. PMID:17329260

  7. Induction of the Lytic Cycle Sensitizes Epstein-Barr Virus-Infected B Cells to NK Cell Killing That Is Counteracted by Virus-Mediated NK Cell Evasion Mechanisms in the Late Lytic Cycle

    PubMed Central

    Williams, Luke R.; Quinn, Laura L.; Rowe, Martin

    2015-01-01

    ABSTRACT Epstein-Barr Virus (EBV) persists for the lifetime of the infected host despite eliciting strong immune responses. This persistence requires a fine balance between the host immune system and EBV immune evasion. Accumulating evidence suggests an important role for natural killer (NK) cells in this balance. NK cells can kill EBV-infected cells undergoing lytic replication in vitro, and studies in both humans and mice with reconstituted human immune systems have shown that NK cells can limit EBV replication and prevent infectious mononucleosis. We now show that NK cells, via NKG2D and DNAM-1 interactions, recognize and kill EBV-infected cells undergoing lytic replication and that expression of a single EBV lytic gene, BZLF1, is sufficient to trigger sensitization to NK cell killing. We also present evidence suggesting the possibility of the existence of an as-yet-unidentified DNAM-1 ligand which may be particularly important for killing lytically infected normal B cells. Furthermore, while cells entering the lytic cycle become sensitized to NK cell killing, we observed that cells in the late lytic cycle are highly resistant. We identified expression of the vBcl-2 protein, BHRF1, as one effective mechanism by which EBV mediates this protection. Thus, contrary to the view expressed in some reports, EBV has evolved the ability to evade NK cell responses. IMPORTANCE This report extends our understanding of the interaction between EBV and host innate responses. It provides the first evidence that the susceptibility to NK cell lysis of EBV-infected B cells undergoing lytic replication is dependent upon the phase of the lytic cycle. Induction of the lytic cycle is associated with acquired sensitization to NK cell killing, while progress through the late lytic cycle is associated with acquired resistance to killing. We provide mechanistic explanations for this novel observation, indicating important roles for the BZLF1 immediate early transactivator, the BHRF1 vBcl-2

  8. Systemic Low-Dose UVB Inhibits CD8 T Cells and Skin Inflammation by Alternative and Novel Mechanisms

    PubMed Central

    Rana, Sabita; Rogers, Linda Joanne; Halliday, Gary Mark

    2011-01-01

    Exposure to UVB radiation before antigen delivery at an unirradiated site inhibits functional immunological responses. Mice treated dorsally with suberythemal low-dose UVB and immunized with ova in abdominal skin generated ova-specific CD8 T cells with a significantly decreased activation, expansion, and cytotoxic activity compared with unirradiated mice. UVB also impaired the delayed-type hypersensitivity (DTH) reaction to ova. Transfer of CD4+CD25+ cells from UVB-exposed mice did not suppress the ova-specific CD8 T-cell response or DTH reaction in unexposed mice, confirming that systemic low-dose UVB does not induce long-lived functional regulatory CD4+CD25+ T cells. Repairing cyclobutane pyrimidine dimer–type DNA damage and blocking aryl hydrocarbon receptor signaling also did not reverse the immunosuppressive effect of UVB on ova-specific CD8 T cells and DTH, suggesting that cyclobutane pyrimidine dimers and the aryl hydrocarbon receptor are not required in systemic low-dose UVB-induced immunosuppression. The known UVB chromophore, cis-urocanic acid, and reactive oxygen species triggered the inhibition of DTH caused by UVB, but they were not involved in the modulation of CD8 T cells. These findings indicate that systemic low-dose UVB impedes the primary response of antigen-specific CD8 T cells by a novel mechanism that is independent of pathways known to be involved in systemic suppression of DTH. PMID:21641400

  9. Chiral, J-Aggregate-Forming Dyes for Alternative Signal Modulation Mechanisms in Self-Immolative Enzyme-Activatable Optical Probes.

    PubMed

    Sloniec-Myszk, Jagoda; Resch-Genger, Ute; Hennig, Andreas

    2016-02-11

    Enzyme-activatable optical probes are important for future advances in cancer imaging, but may easily suffer from low signal-to-background ratios unless not optimized. To address this shortcoming, numerous mechanisms to modulate the fluorescence signal have been explored. We report herein newly synthesized probes based on self-immolative linkers containing chiral J-aggregate-forming dyes. Signal modulation by formation of chiral J-aggregates is yet unexplored in optical enzyme probe design. The comprehensive characterization of the probes by absorption, CD, fluorescence, and time-resolved fluorescence spectroscopy revealed dye-dye interactions not observed for the free dyes in solution as well as dye-protein interactions with the enzyme. This suggested that J-aggregate formation is challenging to achieve with current probe design and that interactions of the dyes with the enzyme may interfere with achieving high signal-to-background ratios. The detailed understanding of the interactions provided herein provides valuable guidelines for the future design of similar probes.

  10. Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic β2-adrenergic stimulation in men.

    PubMed

    Hostrup, Morten; Kalsen, Anders; Onslev, Johan; Jessen, Søren; Haase, Christoffer; Habib, Sajad; Ørtenblad, Niels; Backer, Vibeke; Bangsbo, Jens

    2015-09-01

    The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased (P ≤ 0.01) by 97 ± 29 N (means ± SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased (P ≤ 0.01) by 32 ± 8 and 25 ± 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption (V̇o2max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 ± 0.8 kg (P ≤ 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 ± 558 μm(2); P ≤ 0.01) and MHC II fibers (1,277 ± 595 μm(2); P ≤ 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased (P ≤ 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic β2-adrenergic stimulation in humans.

  11. The study of crack resistance of TiAlN coatings under mechanical loading and thermal cycle testing

    SciTech Connect

    Akulinkin, Alexandr Shugurov, Artur Sergeev, Viktor; Panin, Alexey; Cheng, C.-H.

    2015-10-27

    The effect of preliminary ion bombardment of 321 stainless steel substrate on crack resistance of TiAlN coatings at uniaxial tension and thermal cycling is studied. The ion-beam treatment of the substrate is shown to substantially improve the adhesion strength of the coatings that prevents their delamination and spalling under uniaxial tension. The resistance to crack propagation and spalling by the thermal shock is higher in the TiAlN coating deposited onto the substrate subjected to Ti ion bombardment as compared to that in the TiAlN coating deposited onto the initial substrate.

  12. Bithermal fatigue: A simplified alternative to thermomechanical fatigue

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.

    1988-01-01

    A bithermal fatigue test technique was proposed as a simplified alternative to the thermomechanical fatigue test. Both the thermomechanical cycle and the bithermal technique can be used to study nonisothermal fatigue behavior. The difference between the two cycles is that in a conventional thermomechanical fatigue cycle the temperature is continuously varied concurrently with the applied mechanical strains, but in the bithermal fatigue cycle the specimen is held at zero load during the temperature excursions and all the loads are applied at the two extreme temperatures of the cycle. Experimentally, the bithermal fatigue test technique offers advantages such as ease in synchronizing the temperature and mechanical strain waveforms, in minimizing temperature gradients in the specimen gauge length, and in reducing and interpreting thermal fatigue such as the influence of alternate high and low temperatures on the cyclic stress-strain response characteristics, the effects of thermal state, and the possibility of introducing high- and low-temperature deformation mechanisms within the same cycle. The bithermal technique was used to study nonisothermal fatigue behavior of alloys such as single-crystal PWA 1480, single-crystal Rene N4, cast B1900+Hf, and wrought Haynes 188.

  13. Catalytic Cycle of Multicopper Oxidases Studied by Combined Quantum- and Molecular-Mechanical Free-Energy Perturbation Methods.

    PubMed

    Li, Jilai; Farrokhnia, Maryam; Rulíšek, Lubomír; Ryde, Ulf

    2015-07-01

    We have used combined quantum mechanical and molecular mechanical free-energy perturbation methods in combination with explicit solvent simulations to study the reaction mechanism of the multicopper oxidases, in particular, the regeneration of the reduced state from the native intermediate. For 52 putative states of the trinuclear copper cluster, differing in the oxidation states of the copper ions and the protonation states of water- and O2-derived ligands, we have studied redox potentials, acidity constants, isomerization reactions, as well as water- and O2 binding reactions. Thereby, we can propose a full reaction mechanism of the multicopper oxidases with atomic detail. We also show that the two copper sites in the protein communicate so that redox potentials and acidity constants of one site are affected by up to 0.2 V or 3 pKa units by a change in the oxidation state of the other site. PMID:26039490

  14. Catalytic Cycle of Multicopper Oxidases Studied by Combined Quantum- and Molecular-Mechanical Free-Energy Perturbation Methods.

    PubMed

    Li, Jilai; Farrokhnia, Maryam; Rulíšek, Lubomír; Ryde, Ulf

    2015-07-01

    We have used combined quantum mechanical and molecular mechanical free-energy perturbation methods in combination with explicit solvent simulations to study the reaction mechanism of the multicopper oxidases, in particular, the regeneration of the reduced state from the native intermediate. For 52 putative states of the trinuclear copper cluster, differing in the oxidation states of the copper ions and the protonation states of water- and O2-derived ligands, we have studied redox potentials, acidity constants, isomerization reactions, as well as water- and O2 binding reactions. Thereby, we can propose a full reaction mechanism of the multicopper oxidases with atomic detail. We also show that the two copper sites in the protein communicate so that redox potentials and acidity constants of one site are affected by up to 0.2 V or 3 pKa units by a change in the oxidation state of the other site.

  15. The homodimeric ATP-binding cassette transporter LmrA mediates multidrug transport by an alternating two-site (two-cylinder engine) mechanism

    PubMed Central

    van Veen, Hendrik W.; Margolles, Abelardo; Müller, Michael; Higgins, Christopher F.; Konings, Wil N.

    2000-01-01

    The bacterial LmrA protein and the mammalian multidrug resistance P-glycoprotein are closely related ATP-binding cassette (ABC) transporters that confer multidrug resistance on cells by mediating the extrusion of drugs at the expense of ATP hydrolysis. The mechanisms by which transport is mediated, and by which ATP hydrolysis is coupled to drug transport, are not known. Based on equilibrium binding experiments, photoaffinity labeling and drug transport assays, we conclude that homodimeric LmrA mediates drug transport by an alternating two-site transport (two-cylinder engine) mechanism. The transporter possesses two drug-binding sites: a transport-competent site on the inner membrane surface and a drug-release site on the outer membrane surface. The interconversion of these two sites, driven by the hydrolysis of ATP, occurs via a catalytic transition state intermediate in which the drug transport site is occluded. The mechanism proposed for LmrA may also be relevant for P-glycoprotein and other ABC transporters. PMID:10835349

  16. Novel Nitrobenzazolo[3,2-a]quinolinium Salts Induce Cell Death through a Mechanism Involving DNA Damage, Cell Cycle Changes, and Mitochondrial Permeabilization

    PubMed Central

    Vélez, Christian; Cox, Osvaldo; Rosado-Berrios, Carlos A.; Molina, Dennise; Arroyo, Luz; Carro, Sujey; Filikov, Anton; Kumar, Vineet; Malhotra, Sanjay V.; Cordero, Marisol; Zayas, Beatriz

    2014-01-01

    This study reports the capacity of three nitro substituted benzazolo[3,2-a]quinolinium salts NBQs: NBQ 95 (NSC-763304), NBQ 38 (NSC 763305), and NBQ 97 (NSC-763306) as potential antitumor agents. NBQ’s are unnatural alkaloids possessing a positive charge that could facilitate interaction with cell organelles. The anticancer activities of these compounds were evaluated through the National Cancer Institute (NCI) 60 cell line screening which represents diverse histologies. The screening was performed at 10 µM on all cell lines. Results from the NCI screening indicated cytotoxicity activity on six cell lines. In order to explore a possible mechanism of action, a detailed biological activity study of NBQ 95 and NBQ 38 was performed on A431 human epidermoid carcinoma cells to determine an apoptotic pathway involving, cell cycle changes, DNA fragmentation, mutations, mitochondrial membrane permeabilization and caspases activation. DNA fragmentation, cell cycle effects, mutagenesis, mitochondrial permeabilization and activation of caspases were determined by fluorimetry and differential imaging. Our data showed that A431 growth was inhibited with an average IC50 of 30 µM. In terms of the mechanism, these compounds interacted with DNA causing fragmentation and cell cycle arrest at sub G0/G1 stage. Mutagenesis was higher for NBQ 38 and moderate for NBQ 95 Mitochon-drial permeabilization was observed with NBQ 38 and slightly for NBQ 95. Both compounds caused activation of Caspases 3 and 7 suggesting an apoptotic cell death pathway through an intrinsic mechanism. This study reports evidence of the toxicity of these novel compounds with overlapping structural and mechanistic similarities to ellipticine, a known anti-tumor compound. PMID:25243104

  17. [Effect of Elodea nuttallii-immobilized Nitrogen Cycling Bacteria on Nitrogen Removal Mechanism in an Inflow River, Gonghu Bay].

    PubMed

    Han, Hua-yang; Li, Zheng-kui; Wang, Hao; Zhu, Qian

    2016-04-15

    Undisturbed sediment cores and surface water from Qinshui River in Gonghu Bay were collected to carry out a simulation experiment in our laboratory. The remediation effect of Elodea nuttallii-Immobilized Nitrogen Cycling Bacteria (INCB) was applied in the polluted inflow river. The denitrification rate, ANAMMOX rate and nitrogen microorganism diversity were measured by ¹⁵N isotope pairing technology and high-throughput sequencing technology based on 16S rRNA. The TN, NH₄⁺-N, NO₃⁻-N concentrations were reduced by 72.03%, 46.67% and 76.65% in the treatment with addition of Elodea nuttallii and INCB in our laboratory experiment. Meanwhile, denitrification bacteria and ANAMMOX bacteria had synergistic effect with each other. The denitrification and ANAMMOX rates were increased by 165 µmol (m² · h)⁻¹ and 269.7 µmol · (m² · h)⁻¹, respectively. The diversities of denitrification and ANAMMOX bacteria also increased in our experiment. From the level of major phylum, Proteobacteria, Planctomycetes, Acidobbacteria and Bacteroidetes all increased significantly. The results showed that the Elodea nuttallii-INCB assemblage technology could increase the bio-diversity of nitrogen cycling bacteria and promote the ability of nitrogen removal in Qinshui River. PMID:27548961

  18. [Effect of Elodea nuttallii-immobilized Nitrogen Cycling Bacteria on Nitrogen Removal Mechanism in an Inflow River, Gonghu Bay].

    PubMed

    Han, Hua-yang; Li, Zheng-kui; Wang, Hao; Zhu, Qian

    2016-04-15

    Undisturbed sediment cores and surface water from Qinshui River in Gonghu Bay were collected to carry out a simulation experiment in our laboratory. The remediation effect of Elodea nuttallii-Immobilized Nitrogen Cycling Bacteria (INCB) was applied in the polluted inflow river. The denitrification rate, ANAMMOX rate and nitrogen microorganism diversity were measured by ¹⁵N isotope pairing technology and high-throughput sequencing technology based on 16S rRNA. The TN, NH₄⁺-N, NO₃⁻-N concentrations were reduced by 72.03%, 46.67% and 76.65% in the treatment with addition of Elodea nuttallii and INCB in our laboratory experiment. Meanwhile, denitrification bacteria and ANAMMOX bacteria had synergistic effect with each other. The denitrification and ANAMMOX rates were increased by 165 µmol (m² · h)⁻¹ and 269.7 µmol · (m² · h)⁻¹, respectively. The diversities of denitrification and ANAMMOX bacteria also increased in our experiment. From the level of major phylum, Proteobacteria, Planctomycetes, Acidobbacteria and Bacteroidetes all increased significantly. The results showed that the Elodea nuttallii-INCB assemblage technology could increase the bio-diversity of nitrogen cycling bacteria and promote the ability of nitrogen removal in Qinshui River.

  19. Mechanisms of deformation and fracture in high temperature low cycle fatigue of Rene 80 and IN 100

    NASA Technical Reports Server (NTRS)

    Romanoski, G. R., Jr.

    1982-01-01

    Specimens tested for the AGARD strain range partitioning program were investigated. Rene 80 and IN 100 were tested in air and in vacuum; at 871 C, 925 C, and 1000 C; and in the coated and uncoated condition. The specimens exhibited a multiplicity of high-temperature low-cycle fatigue damage. Observations of the various forms of damage were consistent with material and testing conditions and were generally in agreement with previous studies. In every case observations support a contention that failure occurs at a particular combination of crack length and maximum stress. A failure criterion which is applicable in the regime of testing studied is presented. The predictive capabilities of this criterion are straight forward.

  20. Effect of short-time external short circuiting on the capacity fading mechanism during long-term cycling of LiCoO2/mesocarbon microbeads battery

    NASA Astrophysics Data System (ADS)

    Zhang, Lingling; Cheng, Xinqun; Ma, Yulin; Guan, Ting; Sun, Shun; Cui, Yingzhi; Du, Chunyu; Zuo, Pengjian; Gao, Yunzhi; Yin, Geping

    2016-06-01

    Commercial LiCoO2/mesocarbon microbeads (MCMB) batteries (CP475148AR) are short circuited by different contact resistances (0.6 mΩ and 5.0 mΩ) for short times. The short circuited battery is cycled for 1000 times, and the effect of the short-time external short circuiting on the capacity fading mechanism during long-term cycling of LiCoO2/MCMB battery is studied by analyzing the morphology, structure, and electrochemical performance. The results of SEM indicates that the morphology of LiCoO2 material is almost unchanged, except that the particle surface becomes smooth, and the solid electrolyte interphase (SEI) film on the surface of MCMB electrode becomes nonuniform due to the high temperature caused by short circuiting. The lithium ions are more difficult to de-intercalate from the anode and the lattice structure of LiCoO2 degrades according to the results of X-ray diffraction (XRD). The high discharge current caused by short circuiting can damage electrodes, leaving vacancies in structure. The damage of electrode structure can lead to a decrease of diffusion coefficient of lithium (D), so polarization increases and mainly caused by the LiCoO2 electrode. The capacity deterioration of short circuited battery during long-term cycling is mainly caused by the increase of polarization and capacity loss of electrodes.

  1. Effects of 17-AAG on the cell cycle and apoptosis of H446 cells and the associated mechanisms

    PubMed Central

    Zhao, Xuerong; Wang, Jianping; Xiao, Lijun; Xu, Qian; Zhao, Enhong; Zheng, Xin; Zheng, Huachuan; Zhao, Shuang; Ding, Shi

    2016-01-01

    As a heat shock protein 90 inhibitor, 17-allyl-amino-17-demethoxygeldanamycin (17-AAG) has been studied in numerous types of cancer, however the effects of 17-AAG on apoptosis and the cell cycle of H446 cells remain unclear. In the current study, the MTT method was used to evaluate the inhibitory effects of different durations and doses of 17-AAG treatment on the proliferation of H446 cells. The cells were stained with Annexin-fluorescein isothiocyanate/propidium iodide and measured by flow cytometry, and the gene and protein expression levels of signal transducer and activator of transcription 3 (STAT3), survivin, cyclin D1, cyt-C, caspase 9 and caspase 3 were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The results indicated that with treatment with 1.25–20 mg/l 17-AAG for 24 and 48 h, significant inhibition of H446 cell proliferation was observed in a time- and dose-dependent manner. With treatment of 3.125, 6.25 and 12.5 mg/l 17-AAG for 48 h, significant apoptosis and cell cycle arrest was observed. The results indicated that the gene and protein expression levels of STAT3, survivin and cyclin D1 were downregulated, and cyt-C, caspase 9 and caspase 3 were upregulated by 17-AAG in a dose-dependent manner when the cells were treated with 3.125 and 6.25 mg/l 17-AAG for 48 h. The results indicated that 17-AAG is able to inhibit the cell proliferation, induce apoptosis and G2/M arrest and downregulate the gene and protein expression levels of STAT3, survivin and cyclin D1, and upregulate gene and protein expression of cyt-C, caspase 9, caspase 3. PMID:27279418

  2. Alternate Alternates: A Medley of Alternate Assessments.

    ERIC Educational Resources Information Center

    Burdette, Paula J.; Olsen, Ken

    This paper highlights eight states that have implemented alternate assessments for children with disabilities who cannot participate in their state and district-wide assessment programs. The alternate assessment systems in Delaware, Florida, Georgia, Indiana, Minnesota, North Dakota, Utah, and West Virginia are briefly described, along with their…

  3. Investigation of failure mechanisms in silicon based half cells during the first cycle by micro X-ray tomography and radiography

    NASA Astrophysics Data System (ADS)

    Sun, Fu; Markötter, Henning; Dong, Kang; Manke, Ingo; Hilger, Andre; Kardjilov, Nikolay; Banhart, John

    2016-07-01

    Two proof-of-concept batteries were designed and prepared for X-ray microtomography and radiography characterizations to investigate the degradation mechanisms of silicon (Si) based half cells during the first cycle. It is highlighted here for the first time that, apart from the significant volume expansion-induced pulverization, the electrochemical "deactivation" mechanism contributes significantly to the capacity loss during the first charge process. In addition, the unexpected electrochemically inactive Si particles are also believed to substantially decrease the energy density due to the inefficient utilization of loaded active material. These unexpected findings, which cannot be deduced from macroscopic electrochemical characterizations, expand the inherent explanations for performance deterioration of Si-anode material based lithium ion batteries (LIBs) and emphasize the vital value of microscopic techniques in revealing the correlation between macroscopic electrode structure and the overall electrochemical performance.

  4. Cell cycle alterations induced by urban PM2.5 in bronchial epithelial cells: characterization of the process and possible mechanisms involved

    PubMed Central

    2013-01-01

    Background This study explores and characterizes cell cycle alterations induced by urban PM2.5 in the human epithelial cell line BEAS-2B, and elucidates possible mechanisms involved. Methods The cells were exposed to a low dose (7.5 μg/cm2) of Milan winter PM2.5 for different time points, and the cell cycle progression was analyzed by fluorescent microscopy and flow cytometry. Activation of proteins involved in cell cycle control was investigated by Western blotting and DNA damage by 32P-postlabelling, immunostaining and comet assay. The formation of reactive oxygen species (ROS) was quantified by flow cytometry. The role of PM organic fraction versus washed PM on the cell cycle alterations was also examined. Finally, the molecular pathways activated were further examined using specific inhibitors. Results Winter PM2.5 induced marked cell cycle alteration already after 3 h of exposure, represented by an increased number of cells (transient arrest) in G2. This effect was associated with an increased phosphorylation of Chk2, while no changes in p53 phosphorylation were observed at this time point. The increase in G2 was followed by a transient arrest in the metaphase/anaphase transition point (10 h), which was associated with the presence of severe mitotic spindle aberrations. The metaphase/anaphase delay was apparently followed by mitotic slippage at 24 h, resulting in an increased number of tetraploid G1 cells and cells with micronuclei (MN), and by apoptosis at 40 h. Winter PM2.5 increased the level of ROS at 2 h and DNA damage (8-oxodG, single- and double stand breaks) was detected after 3 h of exposure. The PM organic fraction caused a similar G2/M arrest and augmented ROS formation, while washed PM had no such effects. DNA adducts were detected after 24 h. Both PM-induced DNA damage and G2 arrest were inhibited by the addition of antioxidants and α-naphthoflavone, suggesting the involvement of ROS and reactive electrophilic metabolites formed via a P

  5. The capacity fading mechanism and improvement of cycling stability in MoS2-based anode materials for lithium-ion batteries.

    PubMed

    Shu, Haibo; Li, Feng; Hu, Chenli; Liang, Pei; Cao, Dan; Chen, Xiaoshuang

    2016-02-01

    Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of electrode materials depends on a deep understanding of their dynamic structural evolution and reaction kinetics in the lithiation process. Herein, thermodynamic phase diagrams and the lithiation dynamics of MoS2-based nanostructures with the intercalation of lithium ions are studied by using first-principles calculations and ab initio molecular dynamics simulations. Our results demonstrate that the continuous intercalation of Li ions induces structural destruction of 2H phase MoS2 nanosheets in the discharge process that follows a layer-by-layer dissociation mechanism. Meanwhile, the intercalation of Li ions leads to a structural transition of MoS2 nanosheets from the 2H to the 1T phase due to the ultralow transition barriers (∼0.1 eV). We find that the phase transition can slow down the dissociation of MoS2 nanosheets during lithiation. The result can be applied to explain extensive experimental observation of the fast capacity fading of MoS2-based anode materials between the first and the subsequent discharges. To suppress the dissociation of MoS2 nanosheets in the lithiation process, we propose a strategy by constructing a sandwich-like graphene/MoS2/graphene structure that indicates high chemical stability, superior conductivity, and high Li-ion mobility in the charge/discharge process, implying the possibility to induce an improvement in the anode cycling performance. This work opens a new route to rational design layered transition-metal disulfide (TMD) anode materials for LIBs with superior cycling stability and electrochemical performance. PMID:26780964

  6. The capacity fading mechanism and improvement of cycling stability in MoS2-based anode materials for lithium-ion batteries.

    PubMed

    Shu, Haibo; Li, Feng; Hu, Chenli; Liang, Pei; Cao, Dan; Chen, Xiaoshuang

    2016-02-01

    Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of electrode materials depends on a deep understanding of their dynamic structural evolution and reaction kinetics in the lithiation process. Herein, thermodynamic phase diagrams and the lithiation dynamics of MoS2-based nanostructures with the intercalation of lithium ions are studied by using first-principles calculations and ab initio molecular dynamics simulations. Our results demonstrate that the continuous intercalation of Li ions induces structural destruction of 2H phase MoS2 nanosheets in the discharge process that follows a layer-by-layer dissociation mechanism. Meanwhile, the intercalation of Li ions leads to a structural transition of MoS2 nanosheets from the 2H to the 1T phase due to the ultralow transition barriers (∼0.1 eV). We find that the phase transition can slow down the dissociation of MoS2 nanosheets during lithiation. The result can be applied to explain extensive experimental observation of the fast capacity fading of MoS2-based anode materials between the first and the subsequent discharges. To suppress the dissociation of MoS2 nanosheets in the lithiation process, we propose a strategy by constructing a sandwich-like graphene/MoS2/graphene structure that indicates high chemical stability, superior conductivity, and high Li-ion mobility in the charge/discharge process, implying the possibility to induce an improvement in the anode cycling performance. This work opens a new route to rational design layered transition-metal disulfide (TMD) anode materials for LIBs with superior cycling stability and electrochemical performance.

  7. Effects of Thermal Cycling on Thermal Expansion and Mechanical Properties of Sic Fiber-reinforced Reaction-bonded Si3n4 Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Palczer, A. R.

    1994-01-01

    Thermal expansion curves for SiC fiber-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 C in nitrogen and in oxygen. The effects of fiber/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fiber direction for both bonding cases were similar to that of the weakly bonded composites, but those normal to the fiber direction for both bonding cases resulted in no net dimensional changes at room temperature, and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fiber and RBSN matrix due to oxidation of the carbon-rich fiber surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites.

  8. Studies on the mechanisms of mammalian cell killing by a freeze-thaw cycle: conditions that prevent cell killing using nucleated freezing

    SciTech Connect

    Shier, W.T.

    1988-04-01

    Normally a freeze-thaw cycle is a very efficient method of killing mammalian cells. However, this report describes conditions that prevent killing of cultured mammalian cells by nucleated freezing at -24 degrees C. Optimal protection from cell killing at -24 degrees C was obtained in isotonic solutions containing an organic cryoprotectant such as dimethyl sulfoxide (DMSO; 10%, v/v), a saccharide such as sucrose over a broad concentration range from 50 to 150 mM, and glucose. Glycerol was also an effective cryoprotectant but other organic solvents were ineffective, although in some cases they appeared to protect cell membranes, while not protecting other vital components. A wide variety of saccharide structures were effective at protecting cells from freeze-thaw killing, with trehalose being particularly effective. The degree of resistance to killing by a freeze-thaw cycle under these conditions varied widely among different cell lines. If toxicity of DMSO was responsible for this variability of cryoprotection, it must have been due to short-term, not longer term, toxicity of DMSO. Studies on the mechanism by which cells are protected from killing under these conditions indicated that neither vitrification of the medium nor the concentrating of components during freezing were involved. One model not eliminated by the mechanistic studies proposes that the organic solvent cryoprotectant component acts by fluidizing membranes under the thawing conditions, so that any holes produced by ice crystals propagating through membranes can reseal during the thawing process. In this model one of the mechanisms by which the saccharide component could act is by entering the cells and stabilizing vital intracellular components. Consistent with this, a freeze-thaw cycle promoted the uptake of labeled sucrose into cultured cells.

  9. Cell cycle arrest and mechanism of apoptosis induction in H400 oral cancer cells in response to Damnacanthal and Nordamnacanthal isolated from Morinda citrifolia.

    PubMed

    Shaghayegh, Gohar; Alabsi, Aied M; Ali-Saeed, Rola; Ali, Abdul Manaf; Vincent-Chong, Vui King; Zain, Rosnah Binti

    2016-10-01

    Oral cancer is the eleventh most prevalent cancer worldwide. The most prevalent oral cancer is oral squamous cell carcinoma (OSCC). Damnacanthal (DAM) and nordamnacanthal (NDAM), the anthraquinone compounds, are isolated from the root of Morinda citrifolia L. (Noni), which has been used for the treatment of several chronic diseases including cancer. The objectives of this study were to evaluate the cytotoxicity, cell death mode, cell cycle, and the molecular mechanism of apoptosis induced by DAM and NDAM on OSCC. The cytotoxic effects of these compounds against OSCC cell lines were determined by MTT assay. The cell death mode was analysed by DNA laddering and FITC-annexin V/PI flow cytometric assays. In addition, the mechanism of apoptosis induced by DAM and NDAM was detected using mitochondrial membrane potential, Cytochrome c, and caspases assays. Finally, the effect of DAM and NDAM on cell cycle phase distribution of OSCC cells was detected by flow cytometry. In the present study, DAM and NDAM showed cytotoxicity towards OSCC cell lines and the maximum growth inhibition for both compounds was observed in H400 cells with IC50 value of 1.9 and 6.8 μg/ml, respectively, after 72 h treatment. The results also demonstrated the inhibition of H400 OSCC cells proliferation, internucleosomal cleavage of DNA, activation of intrinsic apoptosis pathway, and cell cycle arrest caused by DAM and NDAM. Therefore, these findings suggest that DAM and NDAM can be potentially used as antitumor agents for oral cancer therapy. PMID:27488882

  10. The differential expression of alternatively polyadenylated transcripts is a common stress-induced response mechanism that modulates mammalian mRNA expression in a quantitative and qualitative fashion

    PubMed Central

    Hollerer, Ina; Curk, Tomaz; Haase, Bettina; Benes, Vladimir; Hauer, Christian; Neu-Yilik, Gabriele; Bhuvanagiri, Madhuri; Hentze, Matthias W.; Kulozik, Andreas E.

    2016-01-01

    Stress adaptation plays a pivotal role in biological processes and requires tight regulation of gene expression. In this study, we explored the effect of cellular stress on mRNA polyadenylation and investigated the implications of regulated polyadenylation site usage on mammalian gene expression. High-confidence polyadenylation site mapping combined with global pre-mRNA and mRNA expression profiling revealed that stress induces an accumulation of genes with differentially expressed polyadenylated mRNA isoforms in human cells. Specifically, stress provokes a global trend in polyadenylation site usage toward decreased utilization of promoter-proximal poly(A) sites in introns or ORFs and increased utilization of promoter-distal polyadenylation sites in intergenic regions. This extensively affects gene expression beyond regulating mRNA abundance by changing mRNA length and by altering the configuration of open reading frames. Our study highlights the impact of post-transcriptional mechanisms on stress-dependent gene regulation and reveals the differential expression of alternatively polyadenylated transcripts as a common stress-induced mechanism in mammalian cells. PMID:27407180

  11. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-05-28

    The [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} crystallizes at room temperature in the monoclinic system with P2{sub 1}/{sub C} space group. Three phase transitions at T{sub 1} = 226 K, T{sub 2} = 264 K, and T{sub 3} = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10{sup −1}–10{sup 7} Hz frequency range and 203–313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

  12. Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2CuCl4

    NASA Astrophysics Data System (ADS)

    Ben Bechir, M.; Karoui, K.; Tabellout, M.; Guidara, K.; Ben Rhaiem, A.

    2014-05-01

    The [N(CH3)3H]2CuCl4 single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH3)3H]2CuCl4 crystallizes at room temperature in the monoclinic system with P21/C space group. Three phase transitions at T1 = 226 K, T2 = 264 K, and T3 = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10-1-107 Hz frequency range and 203-313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH3)3H]2CuCl4 compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

  13. Rugby-Specific Small-Sided Games Training Is an Effective Alternative to Stationary Cycling at Reducing Clinical Risk Factors Associated with the Development of Type 2 Diabetes: A Randomized, Controlled Trial

    PubMed Central

    Mendham, Amy E.; Duffield, Rob; Coutts, Aaron J.; Marino, Frank; Boyko, Andriy; Bishop, David J.

    2015-01-01

    Introduction The present study investigated whether rugby small-sided games (SSG) could be an effective alternative to continuous stationary cycling (CYC) training at reducing clinical risk factors associated with the development of type 2 diabetes mellitus (T2DM). Methods Thirty-three middle-aged (48.6±6.6y), inactive men were randomized into a CYC (n=11), SSG (n=11), or control (CON, n=11) group. Participants trained 3d.wk-1 for 8 weeks, while control participants maintained normal activity and dietary patterns. Exercise duration was matched between groups, which involved CYC or SSG (four quarters, interspersed with 2-min passive recovery). Both training programs were designed to induce similar internal loads of maximal heart rate (~80-85%HRmax) and rating of perceived exertion. Pre- and post-intervention testing included dual-energy x-ray absorptiometry scan, graded exercise test, fasting 2h oral glucose tolerance test and resting muscle biopsy. Western blotting was used to assess the content of skeletal muscle proteins associated with mitochondrial biogenesis and glucose regulation. Results Both CYC and SSG increased VO2 at 80%HRmax, and reduced glycated haemoglobin, glucose area under the curve (AUC; SSG, -2.3±2.4; CYC -2.2±1.6 mmol.L1(120min)1; p<0.05), and total body fat-mass (SSG -2.6±0.9%; CYC -2.9±1.1%), compared to no change in CON (p<0.05). SSG reduced insulin AUC (-30.4±40.7 µlU.mL1(120min)1; p<0.05) and increased total body fat-free mass (1.1±1.2kg; p<0.05), with no change in CYC or CON (P>0.05). There were no differences within or between conditions for protein content of peroxisome proliferator-activated receptor gamma coactivator-1α, sirtuin-1, p53, glucose transporter-4, protein kinase AKT/PKB, myocyte enhancer factor 2A, mitochondrial transcription factor, nuclear respiratory factor (NRF)-1, NRF-2 or mitochondrial complexes I-V (p>0.05). Conclusion Rugby small-sided games is an effective alternative to continuous cycling for improving

  14. Alternative Therapies

    MedlinePlus

    ... Late Effects of Poliomyelitis for Physicians and Survivors © Alternative Therapies Alternative therapies, also called complementary, can support ... of motion, pain, and fatigue are often reported. Energy work includes acupuncture and acupressure, traditional Chinese medicine ...

  15. Investigation of the mechanical behaviour of the plantar soft tissue during gait cycle: Experimental and numerical activities.

    PubMed

    Fontanella, Chiara G; Forestiero, Antonella; Carniel, Emanuele L; Natali, Arturo N

    2015-10-01

    The aim of this work is to investigate the mechanical response of the plantar soft tissue from the heel strike to the midstance, developing both experimental and numerical activities. Using force plates and motion tracking system, the dynamic and kinematic data of 10 subjects are evaluated. The average kinematics data obtained from the experimental tests are assumed as boundary and loading conditions for the computational analyses. A three-dimensional virtual solid model of the foot is developed from the analysis of Digital Imaging and Communications in Medicine images from computed tomography and magnetic resonance. Constitutive formulations that interpret the mechanical response of the biological tissues are defined. Because of the major role of plantar soft tissue in the proposed analysis, a specific visco-hyperelastic constitutive formulation is provided considering the typical features of the tissue mechanics. The three-dimensional numerical model permits to evaluate the capability of the plantar soft tissue to redistribute the deformations, especially during the midstance, and to define quantitative aspects related to the energy absorption. The numerical results highlight the stress distribution from the heel strike to the midstance. The values of stress and strain reached are more intensive during the midstance, when there is a single support of the foot.

  16. Droughts may increase susceptibility of prairie dogs to fleas: Incongruity with hypothesized mechanisms of plague cycles in rodents

    USGS Publications Warehouse

    Eads, David; Biggins, Dean E.; Long, Dustin H.; Gage, Kenneth L.; Antolin, Michael F.

    2016-01-01

    Plague is a reemerging, rodent-associated zoonosis caused by the flea-borne bacterium Yersinia pestis. As a vector-borne disease, rates of plague transmission may increase when fleas are abundant. Fleas are highly susceptible to desiccation under hot-dry conditions; we posited that their densities decline during droughts. We evaluated this hypothesis with black-tailed prairie dogs (Cynomys ludovicianus) in New Mexico, June–August 2010–2012. Precipitation was relatively plentiful during 2010 and 2012 but scarce during 2011, the driest spring–summer on record for the northeastern grasslands of New Mexico. Unexpectedly, fleas were 200% more abundant in 2011 than in 2010 and 2012. Prairie dogs were in 27% better condition during 2010 and 2012, and they devoted 287% more time to grooming in 2012 than in 2011. During 2012, prairie dogs provided with supplemental food and water were in 23% better condition and carried 40% fewer fleas. Collectively, these results suggest that during dry years, prairie dogs are limited by food and water, and they exhibit weakened defenses against fleas. Long-term data are needed to evaluate the generality of whether droughts increase flea densities and how changes in flea abundance during sequences of dry and wet years might affect plague cycles in mammalian hosts.

  17. Verification of a 2 kWe Closed-Brayton-Cycle Power Conversion System Mechanical Dynamics Model

    NASA Technical Reports Server (NTRS)

    Ludwiczak, Damian R.; Le, Dzu K.; McNelis, Anne M.; Yu, Albert C.; Samorezov, Sergey; Hervol, Dave S.

    2005-01-01

    Vibration test data from an operating 2 kWe closed-Brayton-cycle (CBC) power conversion system (PCS) located at the NASA Glenn Research Center was used for a comparison with a dynamic disturbance model of the same unit. This effort was performed to show that a dynamic disturbance model of a CBC PCS can be developed that can accurately predict the torque and vibration disturbance fields of such class of rotating machinery. The ability to accurately predict these disturbance fields is required before such hardware can be confidently integrated onto a spacecraft mission. Accurate predictions of CBC disturbance fields will be used for spacecraft control/structure interaction analyses and for understanding the vibration disturbances affecting the scientific instrumentation onboard. This paper discusses how test cell data measurements for the 2 kWe CBC PCS were obtained, the development of a dynamic disturbance model used to predict the transient torque and steady state vibration fields of the same unit, and a comparison of the two sets of data.

  18. Alternative methods for disposal of spent laying hens: evaluation of the efficacy of grinding, mechanical deboning, and of keratinase in the rendering process.

    PubMed

    Freeman, S R; Poore, M H; Middleton, T F; Ferket, P R

    2009-10-01

    Besides the challenges of mortality and litter disposal, the poultry industry must find economical means of disposing of laying hens that have outlived their productive lives. Because spent hens have low market value and disposing of them by composting and burial is often infeasible, finding alternative disposal methods that are environmentally secure is prudent. The feasibility of grinding or mechanically deboning spent hens with and without prior mechanical picking was evaluated for the production of various proteinaceous by-product meals. The end products were analyzed for nutrient content and found to be high in protein (35.3-91.9% CP) and, with the exception of the feathers, high in fat (24.1-58.3%), making them potentially valuable protein and energy sources. After considering physical and economic feasibility, mechanical deboning was determined to be a logical first step for the conversion of spent hens into value-added by-product meals. Because the hard tissue fraction (primarily feathers, bones, and connective tissue) generated by mechanically deboning the hens presents the greatest challenge to their utilization as feedstuffs, attention was focused on technologies that could potentially improve the nutritional value of the hard tissue for use as a ruminant protein source. Traditional hydrolysis of this hard tissue fraction improved its pepsin digestibility from 74% to 85%; however, subsequent keratinase enzyme treatment for 1h, 2h, 4h, or 20 h after steam hydrolysis failed to improve the pepsin or amino acid digestibility any further (P>0.10). Enzyme hydrolysis did, however, increase the quantities of the more soluble protein fractions (A: 45.5, 46.6, 52.8, 51.6, and 55.8% of CP; B(1): 3.2, 9.8, 6.0, 4.6, and 4.1% of CP; B(2): 11.7, 18.1, 22.8, 29.6, and 22.0% of CP for 0, 1h, 2h, 4h, and 20 h, respectively) and reduced quantities of the less soluble fractions (B(3): 30.2, 18.1, 10.8, 5.5, and 10.2% of CP; C: 9.4, 7.5, 7.6, 8.8, and 7.9% of CP for 0, 1h

  19. Temperature-Dependent Effects on the Mechanical Behavior and Deformation Substructure of Haynes 188 Under Low-Cycle Fatigue

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The mechanical behavior of a cobalt-nickel-chromium-tungsten superalloy, Haynes 188, is being critically examined at the NASA Lewis Research Center. This dynamic, strain-aging (DSA) alloy is used for combustor liners in many military and commercial aircraft turbine engines and for the liquid oxygen posts in the main injectors of the space shuttle main engine. Its attractive features include a good combination of high monotonic yield and tensile strength, and excellent fabricability, weldability, and resistance to high-temperature oxidation for prolonged exposures.

  20. Characterization of Arabidopsis fluoroacetate-resistant mutants reveals the principal mechanism of acetate activation for entry into the glyoxylate cycle.

    PubMed

    Turner, James E; Greville, Karen; Murphy, Elaine C; Hooks, Mark A

    2005-01-28

    The toxic acetate analogue monofluoroacetic acid was employed to isolate Arabidopsis tDNA-tagged plants deficient in their ability to utilize or sense acetate. Several tDNA-tagged lines were isolated, including two that were determined to be allelic to an EMS-mutagenized line denoted acn1 for ac non-utilizing. Following conventions, the tDNA-tagged mutants were designated acn1-2 and acn1-3. Both mutants displayed identical behavior to acn1-1 on a variety of fluorinated and nonfluorinated organic acids, indicating that resistance was specific to fluoroacetate. Thermal asymmetric interlaced PCR identified the sites of tDNA insertion in both mutants to be within different exons in a gene, which encoded a protein containing an AMP-binding motif. Reverse transcription-PCR confirmed that the gene was not expressed in the mutants, and quantitative reverse transcription-PCR showed that the gene is expressed in imbibed seeds and increases in amount during establishment. The wild type AMP-binding protein cDNA was cloned and expressed in Escherichia coli, and the expressed protein was purified by nickel chelate chromatography. The enzyme was identified as an acyl-CoA synthetase that was more active with acetate than butyrate and was not active with fatty acids longer than C-4. The enzyme was localized to peroxisomes by enzymatic analysis of organellar fractions isolated by sucrose density gradient centrifugation. Labeling studies with [(14)C]acetate showed that acn1 seedlings, like those of the isocitrate lyase mutant icl-1 (isocitrate lyase), are compromised in carbohydrate synthesis, indicating that this enzyme is responsible for activating exogenous acetate to the coenzyme A form for entry into the glyoxylate cycle.

  1. Sex-Related Differences in Self-Paced All Out High-Intensity Intermittent Cycling: Mechanical and Physiological Responses

    PubMed Central

    Panissa, Valéria L. G.; Julio, Ursula F.; França, Vanessa; Lira, Fabio S.; Hofmann, Peter; Takito, Monica Y.; Franchini, Emerson

    2016-01-01

    The purpose of this study was to compare sex-related responses to a self-paced all out high-intensity intermittent exercise (HIIE). 9 women and 10 men were submitted to a maximal incremental test (to determine maximum aerobic power - MAP and VO2peak), and an HIIE cycling (60x8s:12s, effort:pause). During the protocol the mean value of V̇O2 and heart rate for the entire exercise (VO2total and HRtotal) as well as the values only in the effort or pause (V̇O2effort, VO2pause and HReffort and HRpause) relative to VO2peak were measured. Anaerobic power reserve (APR), blood lactate [La] and the respiratory exchange ratio (RER) were also measured. These variables were compared between men and women using the unpaired t test. Men used greater APR (109 ± 12%MAP vs 92 ± 6%MAP) with similar V̇O2total (74 ± 7 vs 78 ± 8% VO2peak), however, when effort and pause were analysed separately, V̇O2effort (80 ± 9 vs 80 ± 5%VO2peak) was similar between sexes, while V̇O2pause was lower in men (69 ± 6% vs 77 ± 11% VO2peak, respectively). Women presented lower power decrement (30 ± 11 vs 11 ± 3%), RER (1.04 ± 0.03 vs 1.00 ± 0.02) and [La]peak (8.6 ± 0.9 vs 5.9 ± 2.3 mmol.L-1). Thus, we can conclude that men self-paced HIIE at higher APR but with the same cardiovascular/aerobic solicitation as women. Key points Men self-paced high-intensity intermittent exercise at higher intensities than women. Men utilized greater anaerobic power reserve than women. Men and women had same cardiovascular solicitation. PMID:27274678

  2. Alternative strategies: a better alternative.

    PubMed

    Doody, Dennis

    2010-05-01

    Alternatives can be defined as being any financial asset other than traditional stocks and bonds. They include marketable alternatives, private capital, and equity real estate. There are two primary reasons for investing in alternatives: the potential for greater return and the opportunity to diversify a portfolio. Although alternatives were challenged in the highly volatile environment that existed in 2008 and early 2009, they generally lived up to expectations.

  3. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing: Preprint

    SciTech Connect

    Spataru, Sergiu; Hacke, Pater; Sera, Dezso

    2015-09-15

    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. From the analysis we determine three main categories of failure modes associated with the module degradation consisting of: shunting, recombination losses, increased series resistance losses, and current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test, and initial and final module flash testing, to determine the power degradation characteristic of the module.

  4. HOTS to WATTS - The FPSE linear alternator system re-invented

    NASA Astrophysics Data System (ADS)

    Corey, John A.; Yarr, George A.

    Functional cost analyses of recent free-piston Stirling engines with linear alternators show that the majority of the manufacturing cost is in the mechanical to electrical conversion, not in the Stirling cycle. This paper introduces the first fruits of a systems-based redesign: the STAR alternator and Commuter suspension, which replace conventional linear alternator and bearings for less than half the mass and cost. Descriptions are given of the mechanisms, analyses, prototypes and initial test results, including those from a NASA-Lewis Phase I SBIR into this promising new technology.

  5. Limit cycle stability analysis and adaptive control of a multi-compartment model for a pressure-limited respirator and lung mechanics system

    NASA Astrophysics Data System (ADS)

    Chellaboina, VijaySekhar; Haddad, Wassim M.; Li, Hancao; Bailey, James M.

    2010-05-01

    Acute respiratory failure due to infection, trauma or major surgery is one of the most common problems encountered in intensive care units, and mechanical ventilation is the mainstay of supportive therapy for such patients. In this article, we develop a general mathematical model for the dynamic behaviour of a multi-compartment respiratory system in response to an arbitrary applied inspiratory pressure. Specifically, we use compartmental dynamical system theory and Poincaré maps to model and analyse the dynamics of a pressure-limited respirator and lung mechanics system, and show that the periodic orbit generated by this system is globally asymptotically stable. Furthermore, we show that the individual compartmental volumes, and hence the total lung volume, converge to steady-state end-inspiratory and end-expiratory values. Finally, we develop a model reference direct adaptive controller framework for the multi-compartmental model of a pressure-limited respirator and lung mechanics system where the plant and reference model involve switching and time-varying dynamics. We then apply the proposed adaptive feedback controller framework to stabilise a given limit cycle corresponding to a clinically plausible respiratory pattern.

  6. Neuro-mechanical adjustments to shod versus barefoot treadmill runs in the acute and delayed stretch-shortening cycle recovery phases.

    PubMed

    Morio, Cedric; Sevrez, Violaine; Chavet, Pascale; Berton, Eric; Nicol, Caroline

    2016-01-01

    In habitually shod recreational runners, we studied the combined influence of footwear and stretch-shortening cycle (SSC) fatigue on treadmill running pattern, paying special attention to neuro-mechanical adjustments in the acute and 2-day delayed recovery periods. The SSC exercise consisted of a series of 25 sub-maximal rebounds on a sledge apparatus repeated until exhaustion. The acute and delayed functional fatigue effects were quantified in a maximal drop jump test. The neuro-mechanical adjustments to fatigue were examined during two submaximal treadmill run tests of 3 min performed either barefoot or with shoes on. Surface electromyographic (EMG) activities, tibial accelerations and kinematics of the right lower limb were recorded during the first and last 15 s of each run. The main result was that neuro-mechanical differences between the shod and barefoot running patterns, classically reported in the absence of fatigue, persisted in the fatigued state. However, in the delayed recovery phase, rearfoot eversion was found to significantly increase in the shod condition. This specific footwear effect is considered as a potential risk factor of overuse injuries in longer runs. Therefore, specific care should be addressed in the delayed recovery phase of SSC fatigue and the use of motion control shoes could be of interest.

  7. Neuro-mechanical adjustments to shod versus barefoot treadmill runs in the acute and delayed stretch-shortening cycle recovery phases.

    PubMed

    Morio, Cedric; Sevrez, Violaine; Chavet, Pascale; Berton, Eric; Nicol, Caroline

    2016-01-01

    In habitually shod recreational runners, we studied the combined influence of footwear and stretch-shortening cycle (SSC) fatigue on treadmill running pattern, paying special attention to neuro-mechanical adjustments in the acute and 2-day delayed recovery periods. The SSC exercise consisted of a series of 25 sub-maximal rebounds on a sledge apparatus repeated until exhaustion. The acute and delayed functional fatigue effects were quantified in a maximal drop jump test. The neuro-mechanical adjustments to fatigue were examined during two submaximal treadmill run tests of 3 min performed either barefoot or with shoes on. Surface electromyographic (EMG) activities, tibial accelerations and kinematics of the right lower limb were recorded during the first and last 15 s of each run. The main result was that neuro-mechanical differences between the shod and barefoot running patterns, classically reported in the absence of fatigue, persisted in the fatigued state. However, in the delayed recovery phase, rearfoot eversion was found to significantly increase in the shod condition. This specific footwear effect is considered as a potential risk factor of overuse injuries in longer runs. Therefore, specific care should be addressed in the delayed recovery phase of SSC fatigue and the use of motion control shoes could be of interest. PMID:26222328

  8. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-04-21

    [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ≈ 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1} = 255 K, T{sub 2} = 282 K, T{sub 3} = 302 K, T{sub 4} = 320 K, and T{sub 5} = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup −1}-10{sup 7} Hz frequency range and 233–363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

  9. Surface topography, nano-mechanics and secondary structure of wheat gluten pretreated by alternate dual-frequency ultrasound and the correlation to enzymolysis.

    PubMed

    Zhang, Yanyan; Wang, Bei; Zhou, Cunshan; Atungulu, Griffiths G; Xu, Kangkang; Ma, Haile; Ye, Xiaofei; Abdualrahman, Mohammed A Y

    2016-07-01

    The effects of alternate dual-frequency ultrasound (ADFU) pretreatment on the degree of hydrolysis (DH) of wheat gluten (WG) and angiotensin I-converting enzyme (ACE) inhibitory activity were investigated in this research. The surface topography, nano-mechanics and secondary structure of WG were also determined using atomic force microscope (AFM) and circular dichroism (CD). The correlations of ACE inhibitory activity and DH with surface topography, nano-mechanics and secondary structure of WG were determined using Pearson's correlation analysis. The results showed that with an increase in either pretreatment duration or power, the ACE inhibitory activity of the hydrolysate also increases, reaching maximum at 10 min and 150 W/L, respectively, and then decreases thereafter. Similarly, AFM analysis showed that as the pretreatment duration or power increases, the surface roughness also increase and again a decrease occurs thereafter. As the pretreatment duration or power increased, the Young's modulus and adhesion of WG also increased and then declined. Young's modulus and adhesions average values were compared with ACE inhibitory activity reversely. The result of the CD spectra analysis exhibited losses in the relative percentage of α-helix of WG. Pearson's correlation analysis showed that the average values of Young's modulus and the relative percentage of α-helix correlated with ACE inhibitory activity of the hydrolysates linearly and significantly (P<0.05); the relative percentage of β-sheet correlated linearly with DH of WG significantly (P<0.05). In conclusion, ADFU pretreatment is an efficient method in proteolysis due to its physical and chemical effect on the Young's modulus, α-helix and β-sheet of WG.

  10. Mechanism of transient binding and release of substrate protein during the allosteric cycle of the p97 nanomachine.

    PubMed

    Tonddast-Navaei, Sam; Stan, George

    2013-10-01

    ATPases associated with various cellular activities (AAA+) form a superfamily of ring-shaped motor proteins that utilize cyclical allosteric motions to remodel or translocate substrate proteins (SP) through a narrow central pore. The p97 ATPase is a homohexameric, double-ring member of this superfamily that encloses a central channel with nonuniform width. A narrow compartment is present within the D1 ring and a larger cavity within the D2 ring, separated by a constriction formed by six His amino acids. We use molecular dynamics simulations to probe the interaction between p97 and an extended peptide substrate. Mechanical pulling of the substrate through the p97 pore reveals that smaller work is required for translocation from the D1 toward the D2 compartment than in the opposite direction. These distinct energetic requirements originate in structural aspects and chemical properties of the pore lining. Whereas van der Waals interactions are dominant within the D1 pore, interaction within the D2 pore are strongly electrostatic. Two charged amino acids in the D2 pore, Arg599 and Glu554, provide the largest contribution to the interaction and hinder translocation from the D2 pore. SP threading requires smaller forces when the SP is pulled from the D1 side due to lower barrier to rotation of the His side chains in the direction of the D2 pore. Based on additional simulations of SP binding to two allosteric conformations of p97, we propose that transient binding and release of SP from the pore involves a lever mechanism. Binding to the open pore conformation of p97 occurs primarily at the Arg599 side chain, where the SP backbone is engaged through electrostatic interactions and hydrogen bonds. ATP-driven conformational transitions within the D2 ring alter the chemical environment inside the p97 cavity in the closed pore state. In this state, Glu554 side chains project further into the pore and interacts strongly through van der Waals contacts with the SP backbone. Based

  11. Alternative backing up pump for turbomolecular pumps

    DOEpatents

    Myneni, Ganapati Rao

    2003-04-22

    As an alternative to the use of a mechanical backing pump in the application of wide range turbomolecular pumps in ultra-high and extra high vacuum applications, palladium oxide is used to convert hydrogen present in the evacuation stream and related volumes to water with the water then being cryo-pumped to a low pressure of below about 1.e.sup.-3 Torr at 150.degree. K. Cryo-pumping is achieved using a low cost Kleemenco cycle cryocooler, a somewhat more expensive thermoelectric cooler, a Venturi cooler or a similar device to achieve the required minimization of hydrogen partial pressure.

  12. Proposing interactions between maternal phospholipids and the one carbon cycle: A novel mechanism influencing the risk for cardiovascular diseases in the offspring in later life.

    PubMed

    Khot, Vinita; Chavan-Gautam, Preeti; Joshi, Sadhana

    2015-05-15

    Studies have adequately demonstrated the importance of maternal nutrition, particularly, micronutrients (folic acid, vitamin B12) and long chain polyunsaturated fatty acids (LCPUFAs) in determining pregnancy outcome. Reports indicate that children born preterm or to mothers with preeclampsia are at increased risk of developing cardiovascular diseases (CVD) in later life although mechanisms are unclear. Our earlier studies have established that micronutrients (folic acid, vitamin B12) and LCPUFAs are interlinked in the one carbon cycle and influence methylation reactions. Here, we propose a novel hypothesis that altered phospholipid metabolism and dysregulation in the one carbon cycle will result in altered epigenetic programming of placental genes leading to an adverse pregnancy outcome with increased risk of adult diseases in the offspring. Folic acid and vitamin B12 are involved in S-adenosylmethionine (SAM) synthesis, the major methyl donor for most methyl acceptors. Inadequacy of LCPUFA containing phospholipids, one of the major methyl group acceptors in the one carbon metabolic pathway, may cause diversion of methyl groups toward deoxyribonucleic acid (DNA) eventually resulting in aberrant DNA methylation patterns. These modified DNA methylation patterns lead to alterations in the expression of vital genes e.g. angiogenic factor genes thereby contributing to the dysregulation of angiogenesis/vasculogenesis further affecting placental development. This consequently would adversely "program" the fetus for increased risk of CVD in later life. PMID:25283080

  13. Urinary loss of tricarboxylic acid cycle intermediates as revealed by metabolomics studies: an underlying mechanism to reduce lipid accretion by whey protein ingestion?

    PubMed

    Lillefosse, Haldis H; Clausen, Morten R; Yde, Christian C; Ditlev, Ditte B; Zhang, Xumin; Du, Zhen-Yu; Bertram, Hanne C; Madsen, Lise; Kristiansen, Karsten; Liaset, Bjørn

    2014-05-01

    Whey protein intake is associated with the modulation of energy metabolism and altered body composition both in human subjects and in animals, but the underlying mechanisms are not yet elucidated. We fed obesity-prone C57BL/6J mice high-fat diets with either casein (HF casein) or whey (HF whey) for 6 weeks. At equal energy intake and apparent fat and nitrogen digestibility, mice fed HF whey stored less energy as lipids, evident both as lower white adipose tissue mass and as reduced liver lipids, compared with HF-casein-fed mice. Explorative analyses of 48 h urine, both by (1)H NMR and LC-MS metabolomic platforms, demonstrated higher urinary excretion of tricarboxylic acid (TCA) cycle intermediates citric acid and succinic acid (identified by both platforms), and cis-aconitic acid and isocitric acid (identified by LC-MS platform) in the HF whey, relative to in the HF-casein-fed mice. Targeted LC-MS analyses revealed higher citric acid and cis-aconitic acid concentrations in fed state plasma, but not in liver of HF-whey-fed mice. We propose that enhanced urinary loss of TCA cycle metabolites drain available substrates for anabolic processes, such as lipogenesis, thereby leading to reduced lipid accretion in HF-whey-fed compared to HF-casein-fed mice.

  14. Evolution of a developmental mechanism: species-specific regulation of the cell cycle and the timing of events during craniofacial osteogenesis

    PubMed Central

    Hall, Jane; Jheon, Andrew H.; Ealba, Erin L.; Eames, B. Frank; Butcher, Kristin D.; Mak, Siu-Shan; Ladher, Raj; Alliston, Tamara; Schneider, Richard A.

    2014-01-01

    Neural crest mesenchyme (NCM) controls species-specific pattern in the craniofacial skeleton but how this cell population accomplishes such a complex task remains unclear. To elucidate mechanisms through which NCM directs skeletal development and evolution, we made chimeras from quail and duck embryos, which differ markedly in their craniofacial morphology and maturation rates. We show that quail NCM, when transplanted into duck, maintains its faster timetable for development and autonomously executes molecular and cellular programs for the induction, differentiation, and mineralization of bone, including premature expression of osteogenic genes such as Runx2 and Col1a1. In contrast, the duck host systemic environment appears to be relatively permissive and supports osteogenesis independently by providing circulating minerals and a vascular network. Further experiments reveal that NCM establishes the timing of osteogenesis by regulating cell cycle progression in a stage- and species-specific manner. Altering the time-course of D-type cyclin expression mimics chimeras by accelerating expression of Runx2 and Col1a1. We also discover higher endogenous expression of Runx2 in quail coincident with their smaller craniofacial skeletons, and by prematurely over-expressing Runx2 in chick embryos we reduce the overall size of the craniofacial skeleton. Thus, our work suggests that NCM establishes species-specific size in the craniofacial skeleton by controlling cell cycle, Runx2 expression, and the timing of key events during osteogenesis. PMID:24262986