Academic literature on the topic 'Base pair lifetime'
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Journal articles on the topic "Base pair lifetime"
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Ferris, Zachary E., Qiushi Li, and Markus W. Germann. "Substituting Inosine for Guanosine in DNA: Structural and Dynamic Consequences." Natural Product Communications 14, no. 5 (May 1, 2019): 1934578X1985003. http://dx.doi.org/10.1177/1934578x19850032.
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Inosine differs from the guanosine nucleoside only by the absence of the N2 amino group. Both nucleosides also have similar electrostatic potentials. Therefore, substituting I for G has been used to probe various properties of nucleic acids and to facilitate the interpretation of binding studies. In particular, the absence of the amino group permits the assessment of its importance in the binding of ligands to the minor groove of duplex DNA. It has been known for some time that an I-C base pair is of lower stability than a regular G-C base pair, which needs to be considered when making DNA constructs containing inosine. However, it is generally assumed that both base pairs are structurally highly similar. To test this assumption in an identical sequence environment, we have determined the fine structure of two hairpin DNA substrates that differ only in the substitution of an I-C base pair for a G-C base pair. The structures have been solved using nuclear magnetic resonance (NMR) restraints in conjunction with Mardigras and molecular dynamics. The structural data are complemented with thermodynamic and dynamic data to get a comprehensive evaluation of the consequences of G-C vs I-C base pair substitutions. Our data show a strong similarity in the structures of the hairpins, but a significant difference in the melting temperatures, T m. This difference is also reflected in the drastically decreased base pair lifetime of 7.4 milliseconds compared to the G-C base pair lifetime of 155 milliseconds. The substitution of I-C for G-C is to probe for specific effect due to the amino group is satisfactory, as long as the lowered thermal stability and the drastically increased local dynamics are considered.
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McGuinness, Colin D., David Keszenman-Pereyra, Paul Dickinson, Colin J. Campbell, Beatrice A. Maltman, Till T. Bachmann, Peter Ghazal, and Jason Crain. "Base pair mismatch identification with DNA nanoswitch and long lifetime acridine fluorophore." Sensors and Actuators B: Chemical 148, no. 1 (June 2010): 342–46. http://dx.doi.org/10.1016/j.snb.2010.04.047.
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Berkoff, Bruce, Mike Hogan, Jane Legrange, and Robert Austin. "Dependence of oxygen quenching of intercalated methylene blue triplet lifetime on DNA base-pair composition." Biopolymers 25, no. 2 (February 1986): 307–16. http://dx.doi.org/10.1002/bip.360250211.
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Friederich, F., T. von Clarmann, B. Funke, H. Nieder, J. Orphal, M. Sinnhuber, G. P. Stiller, and J. M. Wissing. "Lifetime and production rate of NOx in the upper stratosphere and lower mesosphere in the polar spring/summer after the solar proton event in October–November 2003." Atmospheric Chemistry and Physics Discussions 12, no. 7 (July 18, 2012): 17703–21. http://dx.doi.org/10.5194/acpd-12-17703-2012.
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Abstract. We present altitude dependent lifetimes of NOx, determined with MIPAS/ENVISAT, for the southern polar region after the solar proton event in October–November 2003. Varying in latitude and decreasing in altitude they range from about two days at 64 km to about 20 days at 44 km. The lifetimes are controlled by transport, mixing and photolysis. We infer dynamical lifetimes by comparison of the observed decay to photolytical lifetimes calculated with the SLIMCAT 3-D Model. Photochemical loss contributes to the observed NOx depletion by 10% at 44 km, increasing with altitude to 35% at 62 km at a latitude of –63° S. At higher latitudes, the contribution of photochemical loss can be even more important. In addition, we show the correlation of modeled ionization rates and observed NOx densities under consideration of the determined lifetimes of NOx, and calculate altitude dependent effective production rates of NOx due to ionization. For that we compare ionization rates of the AIMOS data base with the MIPAS measurements for the whole Austral polar summer 2003/04. We derive effective NOx-production rates to be applied to the AIMOS ionization rates which range from about 0.2 NOx-molecules per ion pair at 44 km to 0.9 NOx-molecules per ion pair at 54 km at a latitude of –63° S. At –73° S, the NOx-production rate ranges from about 0.2 NOx-molecules per ion pair at 44 km to 1.0 NOx-molecules per ion pair at 60 km. These effective production rates are considerably lower than predicted by box model simulations which could hint at an overestimation of the modeled ionization rates.
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Friederich, F., T. von Clarmann, B. Funke, H. Nieder, J. Orphal, M. Sinnhuber, G. P. Stiller, and J. M. Wissing. "Lifetime and production rate of NO<sub>x</sub> in the upper stratosphere and lower mesosphere in the polar spring/summer after the solar proton event in October–November 2003." Atmospheric Chemistry and Physics 13, no. 5 (March 5, 2013): 2531–39. http://dx.doi.org/10.5194/acp-13-2531-2013.
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Abstract. We present altitude-dependent lifetimes of NOx, determined with MIPAS/ENVISAT (the Michelson Interferometer for Passive Atmospheric Sounding/the European Environment Satellite), for the Southern polar region after the solar proton event in October–November 2003. Between 50° S and 90° S and decreasing in altitude they range from about two days at 64 km to about 20 days at 44 km. The lifetimes are controlled by transport, mixing and photochemistry. We infer estimates of dynamical lifetimes by comparison of the observed decay to photochemical lifetimes calculated with the SLIMCAT 3-D Model. Photochemical loss contributes to the observed NOx depletion by 0.1% at 44 km, increasing with altitude to 45% at 64 km. In addition, we show the correlation of modelled ionization rates and observed NOx densities under consideration of the determined lifetimes of NOx, and calculate altitude-dependent effective production rates of NOx due to ionization. For that we compare ionization rates of the AIMOS data base with the MIPAS measurements from 15 October–31 December 2003. We derive effective NOx-production rates to be applied to the AIMOS ionization rates which range from about 0.2 NOx-molecules per ion pair at 44 km to 0.7 NOx-molecules per ion pair at 62 km. These effective production rates are considerably lower than predicted by box model simulations which could hint at an overestimation of the modelled ionization rates.
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Brümmer, Burghard, Gerd Müller, and Gunnar Noer. "A Polar Low Pair over the Norwegian Sea." Monthly Weather Review 137, no. 8 (August 1, 2009): 2559–75. http://dx.doi.org/10.1175/2009mwr2864.1.
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Abstract During the Lofotes cyclone experiment (LOFZY 2005), two polar lows developed one behind the other inside a cold-air outbreak from the north in the lee of Spitsbergen on 7 March 2005. Buoys, ship, and aircraft measurements as well as satellite imagery are applied to analyze the polar low bulk properties, the horizontal and vertical structure, and the mass, moisture, and heat budget. The lifetime of the system until landfall at northern Norway was 12 h. The generation occurred under the left exit region of an upper-level jet with 70 m s−1. Both polar lows had a radius of 100–130 km and extended to a height of about 2.5 km. The propagation speeds were within 14–17 m s−1 and correspond to the vertically averaged wind velocity of the lowest 2.5 km. In the polar low centers the pressure was about 2–3 hPa lower and the air was 1–2 K warmer and drier than in the surroundings. Aircraft measurements in the second of the two polar lows show an embedded frontlike precipitation band north of the center. Here, the highest low-level winds with 25 m s−1 and the largest fluxes of sensible and latent heat with 290 and 520 W m−2, respectively, were measured (areal averages amounted to 115 and 190 W m−2). Aircraft data show mass convergence in the subcloud layer (0–900 m) and divergence in the cloud layer (900–2500 m). Moisture supply by evaporation from the sea surface was about twice as large as that by convergence in the subcloud layer. The condensation rate in the cloud layer nearly equaled the rate of evaporation at the sea surface. Almost all condensed cloud water was converted to precipitation water. Only half of the precipitation at the cloud base reached the sea surface.
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Sorel, Océane, and Benjamin G. Dewals. "MicroRNAs in large herpesvirus DNA genomes: recent advances." Biomolecular Concepts 7, no. 4 (August 1, 2016): 229–39. http://dx.doi.org/10.1515/bmc-2016-0017.
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AbstractMicroRNAs (miRNAs) are small non-coding RNAs (ncRNAs) that regulate gene expression. They alter mRNA translation through base-pair complementarity, leading to regulation of genes during both physiological and pathological processes. Viruses have evolved mechanisms to take advantage of the host cells to multiply and/or persist over the lifetime of the host. Herpesviridae are a large family of double-stranded DNA viruses that are associated with a number of important diseases, including lymphoproliferative diseases. Herpesviruses establish lifelong latent infections through modulation of the interface between the virus and its host. A number of reports have identified miRNAs in a very large number of human and animal herpesviruses suggesting that these short non-coding transcripts could play essential roles in herpesvirus biology. This review will specifically focus on the recent advances on the functions of herpesvirus miRNAs in infection and pathogenesis.
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McClelland, Robert A., V. M. Kanagasabapathy, and N. Mathivanan. "Kinetics of breakdown of aryl hemiacetals of α-bromoacetophenone. Effect of phenol leaving groups on the lifetimes of tetrahedral intermediates." Canadian Journal of Chemistry 69, no. 12 (December 1, 1991): 2084–93. http://dx.doi.org/10.1139/v91-301.
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The kinetics of breakdown of seven aryl hemiacetals of α-bromoacetophenone (TOH) have been examined, with aryl substituents 4-MeO, 4-Me, 3-Me, H, 3-MeO, 4-Cl, 3-Cl. The hemiacetals were generated as intermediates in the aqueous bromination of α-aryloxystyrenes, where the breakdown of the hemiacetal is the rate-limiting stage in the overall reaction. Base catalysis of the breakdown shows large Brønsted β values (0.8–1.0) and similarly large βlg values (−0.8 to −1.0). These are argued to arise because of a preassociation mechanism in which the hydrogen-bonded intermediate [Formula: see text] loses aryloxide faster than diffusional separation of the acid–base pair. This mechanism is enforced by lifetimes of the deprotonated hemiacetals TO− in the 1010–1012 s−1 range. Such lifetimes were estimated in two independent ways, by extrapolation of data previously obtained for alkyl hemiacetals of α-bromoacetophenone, and through a calculation based upon the experimental catalytic coefficients, and estimates of the acidity constants for TOH and the equilibrium constants for formation of hydrogen-bonded complexes. The pH-independent breakdown has βlg = −1.03, and the point lies near the Brønsted line for the carboxylate catalysts. This, therefore, also occurs by a preassociation mechanism with water as the catalyst forming the intermediate [Formula: see text], which loses aryloxide faster than diffusional separation. Catalysis by hydroxide ion occurs with rate constants of 8 × 109 M−1 s−1 independent of aryl substituent. This represents rate-limiting diffusional encounter of the hemiacetal and hydroxide ion, the hydrogen-bonded intermediate [Formula: see text] rapidly proceeding on to products. Acid catalysis of the hemiacetal breakdown occurs by a class "n" mechanism in which the acid assists departure of the substitued phenol. Alkyl hemiacetals of α-bromoacetophenone break down by a class "e" mechanism where the leaving group is fully protonated before bond cleavage. The class "e" mechanism can be excluded for the aryl derivatives, since rate constants much greater then diffusion are required to explain the observed catalytic coefficients. The different mechanism is followed in order to avoid the fully protonated hemiacetal, which, being of an O-protonated anisole structure, is of very high energy. Key words: hemiacetal kinetics, preassociation, intermediate lifetime.
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Nong, Wan Hua, Fei Gao, Rong Fu, and Xiao Ming Han. "Investigation of Friction Temperature in Railway Disc Brake." Advanced Materials Research 479-481 (February 2012): 202–6. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.202.
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The distribution of temperature on the rubbing surface is an important factor influencing the lifetime of a brake disc. With a copper-base sintered brake pad and a forge steel disc, up-to-brake experiments have been conducted on a full-scale test bench at a highest speed of 200 Km/h and a maximum braking force of 22.5 KN. The temperature distributions on brake disc surface have been acquired by an infrared thermal camera, and the contact pressure on the contact surface of the friction pair has been calculated by the finite element software ABAQUS. The results show that the area and thermal gradient of the hot bands increase with the increase of braking speed and braking force. The hot bands occur in priority at the radial location of r=200 mm and r=300 mm, and move radially in the braking process. The finite element modelling calculation indicates that the distribution of the contact pressure on the disc surface in radial direction is in a "U"-shape. The maximum contact pressure occur at the radial locations of r=200 mm and r=300 mm, and the minimum contact pressure occur in the vicinity of the mean radius of the disc. The conformity of contact pressure distributions with the practical temperature evolutions indicates that the non-uniform distribution of the contact pressure is the factor resulting in the appearance of hot bands on the disc surface.
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Dodson, Dillon S., and Jennifer D. Small Griswold. "Droplet inhomogeneity in shallow cumuli: the effects of in-cloud location and aerosol number concentration." Atmospheric Chemistry and Physics 19, no. 11 (June 4, 2019): 7297–317. http://dx.doi.org/10.5194/acp-19-7297-2019.
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Abstract. Aerosol–cloud interactions are complex, including albedo and lifetime effects that cause modifications to cloud characteristics. With most cloud–aerosol interactions focused on the previously stated phenomena, there have been no in situ studies that focus explicitly on how aerosols can affect large-scale (centimeters to tens of meters) droplet inhomogeneities within clouds. This research therefore aims to gain a better understanding of how droplet inhomogeneities within cumulus clouds can be influenced by in-cloud droplet location (cloud edge vs. center) and the surrounding environmental aerosol number concentration. The pair-correlation function (PCF) is used to identify the magnitude of droplet inhomogeneity from data collected on board the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft, flown during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS). Time stamps (at 10−4 m spatial resolution) of cloud droplet arrival times were measured by the Artium Flight phase-Doppler interferometer (PDI). Using four complete days of data with 81 non-precipitating cloud penetrations organized into two flights of low-pollution (L1, L2) and high-pollution (H1, H2) data shows enhanced inhomogeneities near cloud edge as compared to cloud center for all four cases. Low-pollution clouds are shown to have enhanced overall inhomogeneity, with flight L2 being solely responsible for this enhanced inhomogeneity. Analysis suggests cloud age plays a larger role in the amount of inhomogeneity experienced than the aerosol number concentration, with dissipating clouds showing increased inhomogeneities as compared to growing or mature clouds. Results using a single, vertically developed cumulus cloud demonstrate enhanced droplet inhomogeneity near cloud top as compared to cloud base.
Book chapters on the topic "Base pair lifetime"
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Ezhilchelvan, Paul, Jean-Michel Hélary, and Michel Raynal. "Building TMR-Based Reliable Servers Despite Bounded Input Lifetimes." In Euro-Par 2001 Parallel Processing, 482–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/3-540-44681-8_70.
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Salmon, Catherine, and Jessica Hehman. "Social Versus Sexual Monogamy." In The Oxford Handbook of Infidelity, 121—C6.P161. Oxford University Press, 2022. http://dx.doi.org/10.1093/oxfordhb/9780197502891.013.6.
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Abstract Monogamy is sometimes understood as a type of relationship in which an individual has only one partner during their lifetime. Thus, serial monogamy refers to the practice of having only one partner during a specific period of time. Based on current divorce rates in modern Western populations, humans are often referred to as serially monogamous. However, there is also a distinction to be made between social and sexual monogamy. Social monogamy reflects a socially recognized relationship in which two individuals live together, have sexual relations, and cooperate in the acquisition and sharing of resources, and often the care of offspring. Sexual monogamy consists of two individuals who are sexually exclusive, having no sexual partners outside of the pair. While many pairings can be both socially and sexually monogamous, sexual monogamy is not always found in socially monogamous relationships. This chapter reviews research that examines the factors influencing social and sexual monogamy and the role infidelity can play in social monogamy in humans and nonhuman animals.
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Chłoń-Domińczak, Agnieszka. "Population Ageing and Financing Consumption of the Older Generation in the European Union." In Europe's Income, Wealth, Consumption, and Inequality, 395–427. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197545706.003.0011.
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European countries are facing the challenge of population ageing, and social policies need to adjust to changing intergenerational balance. In this chapter, the most important challenges in the current intergenerational and intragenerational balance are assessed using the National Transfer Accounts approach. Financing the lifecycle deficit of older generations is mainly based on public transfers, while in the case of younger generations it is mainly financed from private transfers. The working-age generation faces a ‘triple burden’ as it finances the lifecycle deficit of older generations by paid taxes and the consumption of the young generation by private transfers. They also need to save more to be able to finance their future consumption to a larger extent from their savings. Recent policy developments show that the pressure of an increase of pension expenditure caused by demographic changes is offset by reducing pension transfers by changing benefit formulae or benefit indexation as well as increasing the effective pensionable age. The span of effective economic activity is relatively short, particularly for women. A gender gap in labor income is also linked to a gender gap in the pension income, which leads to further transfers between men and women at older ages. Income inequalities between older people increase following reforms of pension systems that tighten the link between lifetime earnings and pensions. Mortality differences interact with government programmes for the elderly (e.g., pension systems) and may reduce or even reverse the direction of income redistribution.
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Grätzel, Michael. "Photovoltaic and photoelectrochemical conversion of solar energy." In Energy... beyond oil. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780199209965.003.0010.
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The Sun provides about 100,000 Terawatts (TW) to the Earth, which is approximately ten thousand times greater than the world’s present rate of energy consumption (14 TW). Photovoltaic (PV) cells are being used increasingly to tap into this huge resource and will play a key role in future sustainable energy systems. Indeed, our present needs could be met by covering 0.5% of the Earth’s surface with PV installations that achieve a conversion efficiency of 10%. Fig. 8.1 shows a simple diagram of how a conventional photovoltaic device works. The top and bottom layers are made of an n-doped and p-doped silicon, where the charge of the mobile carriers is negative (electrons) or positive (holes), respectively. The p-doped silicon is made by ‘doping’ traces of an electron-poor element such as gallium into pure silicon, whereas n-doped silicon is made by doping with an electron-rich element such as phosphorus. When the two materials contact each other spontaneous electron and hole transfer across the junction produces an excess positive charge on the side of the n-doped silicon (A) and an excess negative charge on the opposite p-doped (B) side. The resulting electric field plays a vital role in the photovoltaic energy conversion process. Absorption of sunlight generates electron-hole pairs by promoting electrons from the valence band to the conduction band of the silicon. Electrons are minority carriers in the p-type silicon while holes are minority carriers in the n-type material. Their lifetime is very short as they recombine within microseconds with the oppositely charged majority carriers. The electric field helps to collect the photo-induced carriers because it attracts the minority carriers across the junction as indicated by the arrows in Fig. 8.1, generating a net photocurrent. As there is no photocurrent flowing in the absence of a field, the maximum photo-voltage that can be attained by the device equals the potential difference that is set up in the dark at the p-n junction. For silicon this is about 0.7V. So far, solid-state junction devices based on crystalline or amorphous silicon (Si) have dominated photovoltaic solar energy converters, with 94% of the market share.
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Fink MD, Max. "Side Effects and Memory Issues." In Electroconvulsive Therapy. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195365740.003.0008.
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As we have seen, ECT involves modest discomfort, minimal risk, and almost no contraindications to its use. Headache, backache, nausea, and vomiting are the most frequent immediate complaints. These are relieved by mild analgesics and occasionally by the choice of anesthetic. Spine fractures were a complicating risk of the early treatments, but they are now prevented by muscle relaxation. In the past, seizures were sometimes prolonged and did not end promptly. Prolonged seizures are now avoided by precise energy dosing and attention to anesthesia related to the patient’s age. When a prolonged seizure does occur, it is readily recognized and treated. The risk of death during ECT is very low, less than that of women delivering spontaneous births. It is surprising that death is so rare since half of the patients are elderly, many ill with severe systemic infirmities or critical illnesses. The low mortality rate reflects the inherent safety of modern procedures. Indeed, some reports find that the lifetime death rates for hospitalized psychiatric patients who have received ECT are lower than the rates of those who have not. The mortality rate from natural causes is lower for those treated with ECT than for those who have not. Suicide rates are higher, however. The common memory loss associated with ECT is the main hurdle patients and their families face in accepting the treatment. Images of a patient losing the memory of his past life, his work skills, the names of his children and friends, and the ability to care for himself, much like a patient with Alzheimer’s disease, are so prevalent that doctors hesitate to recommend the treatment and many patients refuse permission even when it may be their principal lifesaving option. Such images are false. The fear of memory loss is based largely on reports by patients who were treated without anesthesia or ventilation with oxygen in the first decades of the treatment’s use. Such treatments were accompanied by severe, and often persistent, impairments in memory. Clinical practice changed and our treatments are no longer associated with these devastating problems, as careful attention is now paid to oxygenation throughout the procedure and to technical features that minimize the impact of the stimulus, anesthesia, and the seizure on memory.
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Kidd, Edwina, and Ole Fejerskov. "Introduction." In Essentials of Dental Caries. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780198738268.003.0003.
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A pain-free, functioning, and good-looking dentition for a lifetime seems a reasonable goal! Is this what dentists do? An advertisement for a North American dental practice recently suggested that dentists practising general dentistry provide amalgam and composite fillings, sealants, cosmetic dentistry, pulp and root canal treatment, crown and bridges, dentures, and dental implants. Moreover, they do minor oral surgery, gum disease treatment, and occasionally temporomandibular joint (TMJ) therapy, tobacco cessation, and nutrition counselling. The topics listed in the first sentence comprise the daily work in general dentistry, but do you realize that 85% of these are a direct consequence of dental caries? Yet dental caries is not mentioned as the main reason for most dental treatments. Restorative treatment is the focus of dentistry. The disease dental caries is the only disease which has been combatted with metals and composites for more than a century. Some 50 years ago the concept of prevention became fashionable. Now restorative treatment was described as ‘secondary prophylaxis’ because it was considered that once the inevitable dental caries had occurred, it had to be treated (i.e. restored) to prevent further break down of the teeth and the dentition. Therefore, it is not surprising that the most time in the dental curriculum is devoted to the many skilled restorative procedures. These have to be conducted in a moist, slippery, small, and moving oral cavity attached to a person who may find the procedure unpleasant! No wonder it is difficult to perform intra-oral restorative work of high quality as part of oral rehabilitation, and no wonder so much time in the curriculum is devoted to these aspects. However, supposing it was possible to prevent or control the disease so that restorations are reduced to a minimum? This control of caries is what this book is about! Seven chapters present the essentials of what is known about dental caries. The observations will be based on current scientific evidence. This is a hands-on book, which means that what is suggested and observed should have immediate implications for how patients may be treated.
Conference papers on the topic "Base pair lifetime"
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Sinsuebphon, Nattawut, Travis Bevington, Lingling Zhao, Abe Ken, Margarida Barroso, and Xavier Intes. "Comparison of Near-Infrared Fluorophore Pairs for Lifetime-Based FRET Imaging." In Biomedical Optics. Washington, D.C.: OSA, 2014. http://dx.doi.org/10.1364/biomed.2014.bm3a.39.
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Chen, Sez-Jade, Nattawut Sinsuebphon, Alena Rudkouskaya, Margarida Barroso, and Xavier Intes. "Fluorescence Lifetime-based Multiplexing of Near-Infrared Förster Resonance Energy Transfer Pairs." In Cancer Imaging and Therapy. Washington, D.C.: OSA, 2016. http://dx.doi.org/10.1364/cancer.2016.jm3a.36.
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Shorey-Fennell, Bethany, Renee Magnan, Benjamin Ladd, and Jessica Fales. "What’s Pain Got To Do With It?: Young Adults With and Without Chronic Pain Perceive Minimal Risks and Moderate Benefits from Cannabis Use." In 2020 Virtual Scientific Meeting of the Research Society on Marijuana. Research Society on Marijuana, 2021. http://dx.doi.org/10.26828/cannabis.2021.01.000.9.
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Many young adults experience chronic pain and given its wide availability and potential pain reducing properties, young adults may use cannabis to self-medicate for pain. However, little is known about young adult users’ perceptions of potential health risks and benefits of cannabis, and whether these perceptions differ by chronic pain status. As a part of a larger study, young adult recreational cannabis users (N=176, ages 18-29) who reported using at least once a week completed assessments of use frequency and perceived cannabis-related risks and benefits. The sample had a high proportion of participants who met criteria for chronic pain (51.1%). The majority of the sample reported using daily or multiple times daily (80.7%) with an average of 2.68 (SD=1.42) sessions per day across administration modes (e.g. smoking, edibles, tinctures). Participants answered questions about their lifetime chances of experiencing five cannabis-related risks (personal harm, negative health outcome, negative mental health outcome, harming someone else, increased pain) and benefits (personal benefit, positive health outcome, positive mental health outcome, benefitting someone else, decreased pain; 1=Very low to 7=Very high). Overall, young adult users perceived their risk to be very low (M=1.62, SD=.73) and 40.3% of the sample had an average risk score (combined across the five risk items) of 1.00, while only one participant reported an average risk above 4.00. In particular, participants reported a low lifetime chance of experiencing personal harm (M=1.51, SD=.90), harming someone else (M=1.20, SD=.58), or experiencing increased pain (M=1.24, SD=.74) due to their cannabis use. In contrast, young adult users perceived somewhat high chances of experiencing benefits related to their cannabis use (M=4.78, SD=1.46). In particular, participants perceived a high chance of experiencing reduced pain (M=5.88, SD=1.55), personal benefit (M=4.84, SD=1.86), and positive mental health outcomes (M=4.82, SD=1.77). There was no difference based on pain status on frequency of use, average daily sessions, or perceived risks, and only one difference in perceived benefits. Participants without chronic pain anticipated more personal benefit from cannabis use (M=5.15, SD=1.74) than those with chronic pain (M=4.53, SD=1.94, t(171)=2.21, p=.03). Overall, results suggest young adult recreational users perceive very low risks of their cannabis consumption and moderately high benefits, regardless of pain status. Looking at individual areas of potential risk and benefits may yield targets for future health education campaigns. For example, perceptions of low risk/high benefits regarding mental health outcomes may not be accurate for this heavy using sample.
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Siewerin, Benedikt J., Andreas Dobler, Thomas Tobie, and Karsten Stahl. "Applicability of an Oil Based Calculation Approach for Wear Risk and Wear Lifetime to Grease Lubricated Gear Pairings." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-97439.
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Abstract Gear pairings often run under very high loads. That can result in different kinds of failure modes limiting their lifetime. Many of the known gear failure modes are tribologically influenced. Especially for gear pairs running with lower circumferential speeds or with different surface hardness, (continuous or slow speed) wear is often the lifetime limiting factor. Slow speed wear appears continuously over a longer period of runtime. In many cases, such applications are lubricated with greases. Since the standardized calculation methods (e.g. ISO 6336) do not cover any determination of wear, one common way to predict the wear lifetime is the calculation method according to Plewe. In the associated Plewe diagram the worn off amount of material is correlated to the minimal lubricant film thickness in the tooth contact. The wear intensity decreases for higher film thicknesses. However, this method has certain limits for greases, because the film thickness of a grease, its bleed oil and the base oil is not necessarily the same. Additionally, the consistency and the flow properties have to be considered, because they influence the lubrication supply mechanism (circulating or channeling). Under certain circumstances channeling could be predominant. Although in theory a grease should build a thicker lubricating film than its base oil, experimental investigations have shown higher wear rates in comparison to oil lubrication.
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Moroz, Leonid, Boris Frolov, and Roman Kochurov. "Steam Turbine Rotor Transient Thermo-Structural Analysis and Lifetime Prediction." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57652.
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Market requirements for faster and more frequent power unit start-up events result in a much faster deterioration of equipment, and a shorter equipment lifespan. Significant heat exchange occurs between steam and turbine rotors during the start-up process and even more intensive heat exchange takes place during the condensation phase in cold start-up mode, which leads to further thermal stresses and lifetime reduction. Therefore, the accuracy of lifetime prediction is strongly affected and dependent on the accuracy of transient thermal state prediction. In this study, transient thermal and structural analyses of a 30 MW steam turbine for a combined High and Intermediate pressures (HPIP) rotor during a full cold start cycle is performed and special attention is paid to initial start-up phase with ‘condensation’ thermal BC. All steps for rotor design and the thermal model preparation were done using the AxSTREAM™* software platform. It included the development of a two dimensional model of the rotor, thermal zones and corresponding thermal boundary conditions (heat transfer coefficients and steam temperatures) calculation during turbine start-up and shut down operation. Rotor thermal and structural simulations were done using commercial FE analysis software to evaluate the thermo-stress-strain state of the turbine rotor. Calculation and validation of thermal and structural state of the rotor was done using actual start-up cycle and measured data from a power plant, and it showed good agreement of the calculated and the measured data. Based on the results of thermo-structural analysis, the evaluation of rotor lifetime by means of a low cycle fatigue approach was performed and presented in this paper.
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Moroz, Leonid, Glenn Doerksen, Fernando Romero, Roman Kochurov, and Boris Frolov. "Integrated Approach for Steam Turbine Thermo-Structural Analysis and Lifetime Prediction at Transient Operations." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63547.
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In order to achieve the highest power plant efficiency, original equipment manufacturers (OEMs) continuously increase turbine working parameters (steam temperatures and pressures), improve components design and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermo-stresses, a lifetime consumption of primary components and an increased demand for accurate thermo-structural and LCF simulations. In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermo-structural analysis, reliability and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions, detailed thermal/structural 2D and 3D FE models preparation, components thermal and stress-strain simulation, rotor-casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of ‘steam condensation’ on thermal BC, the level of detailing for thermal zones definition, thermal contacts and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor-stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a low cycle fatigue approach is performed.
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Lin, Yi, Guoqing Feng, Huilong Ren, and Hao Yu. "Research on Collision Strength for Deep Sea Submersible Structures." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20665.
Full textAbstract:
Collision is one of the common accidents during the lifetime of deep sea submersibles. Now scholars have paid more and more attention to research on collision strength. The FEM is adopted to simulate the collision between two submersibles in this paper. Based on the research on some key collision indices, plastic energy absorption, collision force and critical collision speed, the approach of assessing collision strength was obtained. Besides, we discuss the motion lag of the submersibles and consider the impact of some collision parameters, such as water pressure, impact position, angle, and radius of indenter. Finally, some significant conclusions were made.
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Shorey-Fennell, Bethany, Renee Magnan, Benjamin Ladd, and Jessica Fales. "Young adults’ perceptions of cannabis risks, benefits, and quality of life by chronic pain status." In 2021 Virtual Scientific Meeting of the Research Society on Marijuana. Research Society on Marijuana, 2022. http://dx.doi.org/10.26828/cannabis.2022.01.000.33.
Full textAbstract:
Many young adults experience chronic pain and may be more likely to self-medicate with cannabis. The present study examined perceptions of personal risks and benefits of cannabis use among young adult users, assessed if these perceptions varied by chronic pain status, and identified relationships among perceived risks and benefits, health-related quality of life, and cannabis-related problems. Young adult regular cannabis users (n=176), half of whom met criteria for chronic pain, reported their perceptions of lifetime risks and benefits associated with cannabis use, as well as their physical and mental health-related quality of life and cannabis-related problems. Overall, participants perceived low risk associated with their cannabis use and moderate benefits. Perceived risks and benefits of cannabis use were associated with mental, but not physical health-related quality of life. Only perceived risk was associated with cannabis-related problems. Cannabis use, problems, risks, and benefits did not differ by chronic pain status. As expected, young adults without chronic pain reported better physical and mental health-related quality of life than those with chronic pain. Finally, chronic pain status moderated the relationships between perceived benefits and physical health-related quality of life and cannabis problems. The current study offers insight into the role of perceived risks and benefits in young adults’ cannabis use and associations with physical and mental health outcomes. The effects of perceived benefits on physical health-related quality of life and cannabis-related problems may be conditional based on chronic pain status. Future research should further explore the relationship of perceived benefits of cannabis use on health outcomes and cannabis-related problems.
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Takahashi, Shiro, Yuichi Narumi, Kiyoshi Ishihama, Akihito Yokoyama, Toyohiko Tsuge, Masaaki Hayashi, Hidetoshi Takehara, and Norimichi Yamashita. "Analytical Evaluation of Unsteady Thermal Hydraulic Characteristics in Shell and Tube Heat Exchangers." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89389.
Full textAbstract:
Many shell & tube heat exchangers are used in nuclear power plants. Unsteady thermal hydraulic phenomena have been studied in shell & tube heat exchangers to improve their safety and reliability and to extend their lifetime based on experience obtained from long periods of plant operation. We investigated unsteady flow in shell & tube heat exchangers by using computational fluid dynamics (CFD) analyses. The inlet flow on the shell side was separated and flow in several directions. A large part of the flow crossed over the tube bundle, and some parts of the flow took two circuitous roots (up and down) along the inner surface of the shell. Separated circuitous flows collided again where a baffle plate had been cut off. A pair of symmetric vortexes could be seen in that location. Some parts of the circuitous flow moved backwards into the tube bundle due to vortexes. These vortexes were unstable and changed their size and location. A pair of vortexes changed from symmetric to asymmetric. As a result, the direction of flow in the tube bundle near the vortexes changed continuously. Variations in vortexes simulated through CFD analyses could also be seen in tests on the actual size. Fluid temperature fluctuations around tubes were also evaluated through CFD analyses. Unsteady phenomena with changes from symmetric to asymmetric vortexes could be observed in the shell & tube heat exchanger and were simulated through CFD analyses with a detached eddy simulation (DES) turbulence model.
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Doma, A´rpa´d. "Review of the Primary and Secondary Water Chemistry Operation of Paks Nuclear Power Plant From the Point of View of Lifetime Extension." In 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48147.
Full textAbstract:
The review of the water regime used for the Units of Paks Nuclear Power Plant was carried out in 2005, after 18 – 23 years of operation. It was clearly concluded after processing the huge data base of the water regime, that there is nothing to prevent the life time extension of the Units. In 2006, a new water regime was developed that will be applied during the preparation for the life time extension and the extended service life as well. In connection with this work, recommendations were made for some modifications of the previously used water regime. Currently there is no uniform startup and shutdown water regime for WWER-440 Units. Therefore, special attention was paid to developing of a startup water regime, which will be applied for the outages as early as 2008. The summarised recommendations for water regime modification will be subject to international expert review in 2008, and the modifications judged to be implemented will be finalised after the review.