2,249 research outputs found
Removing Love waves from shallow seismic SH-wave data
No full textGeophysical exploration measurements are used to obtain an image of the geological structures of the subsurface, as detailed as possible. To this end, a wavefield is generated by a seismic source. This wavefield propagates through the subsurface, and will partly reflect on boundaries between layers with contrasting properties, and it will partly propagate further into the subsurface. De wavefields that have propagated back to the surface are measured with receivers. When this experiment is repeated several times on different locations, the measured data can be used to obtain the desired image. There are two kinds of seismic waves that can propagate through the subsurface. The ones that are generally used are the pressure waves, or P-waves, where the movement of the particles is parallel to the propagation direction of the wave. The other ones are the shear waves, or S-waves, where the movement of the particles is perpendicular to the propagation direction of the wave. When the particle movement is horizontally polarized (perpendicular to the plane of propagation), this wave type is often decoupled, or in other words, it propagates independently of other wave types. These waves are also called SH-waves. The surface of the Earth behaves as a perfect reflector for SH-waves. This means that all SH-waves that reach the surface will be completely reflected back into the subsurface. When the top layer of the subsurface is thin (smaller than the wavelength of the SH-wave), and when this top layer has a lower wave velocity than deeper layers, then the presence of the surface leads to a kind of surface waves, which were first described by A.E.H. Love, and are therefore called 'Love waves'. Love wave characteristics are: their group velocity is almost equal to the shear wave velocity; since they propagate solely along the surface, they attenuate slowly and are thus often stronger than reflected waves; and they are dispersive. The presence of Love waves deteriorates the quality of the final picture (or seismogram), because they obscure the desired reflections. Existing techniques to remove Love waves from seismic data often perform insufficient, or require certain knowledge about the subsurface. This knowledge is generally not available. Therefore, the ideal method should be one where the measured data alone is sufficient to separate the Love waves from the desired reflection information. The method we describe in this thesis uses the Betti-Rayleigh reciprocity theorem for elastic media. Reciprocity is a mathematical tool to relate two different states to each other. Here, one state is the actual situation, where the medium is bounded by a stress-free surface. The other state is an ideal situation, where there is no surface, and the top layer is extended to infinity. When there is no surface, there are also no surface waves. By applying the reciprocity theorem, we derive an integral equation, from which the Love wave free wavefield can be solved as a function of the data that do contain these surface waves. Other input parameters are the (shear-) wave velocity and the mass density of the top layer, and the source wavelet. When the data are discrete, the integral equation becomes a matrix equation. This can be solved using conventional numerical methods, such as matrix inversion. When the medium is horizontally layered (a so called 1-D medium), the kernel of the matrix equation becomes diagonal in the wave-number domain. Then the matrix equation reduces to a scalar expression. We tested the method on several synthetic datasets. In all cases, the Love waves were completely removed. Even other noise in the form of scattered Love waves was removed, in the cases where it was present. The method also had no problems when the input parameters were chosen wrongly. And when distortions were introduced into the data (distortions like random noise, or the effects of anelastic attenuation), the method still performed well. To test the method on field data, we performed a seismic experiment on the site of the Sofia tunnel (before it was drilled) near Hendrik Ido Ambacht in the Netherlands. The dataset that was the result seemed all right at first. Strong Love waves were indeed present in the data. However, we could not succeed in removing these Love waves with the method. Even worse, the method added noise to the data, to such an extent, that it completely obscured the original data. Although we searched extensively for possible reasons, we were not able to find the exact cause of the bad results. In the final chapter, we made a start to remove the surface waves from coupled P- and SV-wave systems, using the same method as we did for SH-waves. Because P- and SV-waves are coupled, the resulting equations are also coupled. This means that we need all possible source and receiver combinations to remove the surface waves. But it appeared that the equations could be solved independently with regard to the source direction. We validated the theory with an example where we removed the Rayleigh wave from the response of a homogeneousCivil Engineering and Geoscience
THE EFFECTIVENESS OF CEMCEM (Spondiaspinnata (L.f) Kurz) LEAF EXTRACT IN INHIBITING THE GROWTH OF Streptococcus mutans
No full textIntroduction: Dry socket is post-tooth extraction pain characterized by partial or complete loss of blood clots in the alveolar socket. One of the management of dry socket is by using antibiotic therapy. Inappropriate use of antibiotics in addition to being economically wasteful can also cause bacterial resistance to antibiotics. The use of herbal ingredients such as Cemcem (Spondiaspinnata (L.f) Kurz) is one solution. Cemcem leaves are thought to have antibacterial effects because they contain flavonoids, tannins and saponins. This study aims to determine the inhibition of cemcem leaf extract (Spondias pinnata (L.f) Kurz) against the growth of Streptococcus mutans.
Materials and methods: The research method used is the Kirby Bauer method which is a sensitivity test with the agar diffusion method using the disc diffusion technique. In the Kirby Bauer sensitivity test using selective media, namely Muller Hinton Blood Agar media, the inhibition zone created is characterized by a clear zone around the disc. The data obtained were analyzed using the Kruskall Wallis test to determine whether or not there was a significant difference then continued with the Mann Whitney U - Test.
Results: Cemcem leaf extract (Spondias pinnata (L.f) Kurz) with a concentration of 60% and 70% can inhibit the growth of Streptococcus mutans better than positive control and 80% concentration.
Conclusion: 60% concentration of cemcem leaf extract is more effective in inhibiting the growth of Streptococcus mutans than 70% and 80% concentrations
The scientific career of L.F. Obukhova from the 1960s to the 2010s
No full textBackground. Lyudmila Filippovna Obukhova (July 22, 1938 – July 20, 2016) made a great contribution to the study of the developmental psychology. The Objective is to recreate the portrait of L.F. Obukhova retrieved from her personal memories, to identify some features of her personality, to present the most important areas of her research and teaching job in the field of developmental and general psychology, to show her grateful attitude towards parents, teachers, colleagues.
Design. The paper shows that L.F. Obukhova, after graduating from the Department of Psychology at the Faculty of Philosophy, Moscow Lomonosov State University, worked in the field of child psychology. She carried out a comprehensive theoretical and experimental analysis of the Geneva School of Genetic Psychology, established by the eminent Swiss psychologist J.Piaget and his followers. Being a student of P.Ya. Galperin, she worked in the wake of her teacher’s ideas, was a part of his scientific school, conducted lectures on Galperin’s theory and carried out her own research that made a significant contribution to the development of Galperin’s theory. L.F. Obukhova showed that in the stream of all psychological theories of child development, the concepts of Piaget and Galperin are the main approaches to the issue of ontogenetic development. Both of them are fruitful, but Vygotsky cultural-historical school is the most distinguished.
Results. Fruitful activities in the field of developmental psychology, the practical value of textbooks for psychology students allow us to classify L.F. Obukhov as classical Russian psychologist
ANTIMICROBIAL ACTIVITY OF ANISOCHILUS CARNOSUS (L.F.) WALL AGAINST THE HUMAN GASTRIC PATHOGEN HELICOBACTER PYLORI
No full text  Objective: The prevalence of Helicobacter pylori in India is high, and majority leads to severe gastrointestinal infections. Existing treatment regimens for H. pylori infections have increased failure rates and adverse side effects that desire the search for an effective substitute therapy. Anisochilus carnosus (L.f.) wall (Lamiaceae), a herb which grows once in a year at high elevation is used widely in traditional treatment for the complaints of gastric ulcer and skin diseases. The present study was performed to assess the antibacterial activity of A. carnosus (L.f.) wall, against clinical isolates of H. pylori in vitro.Methods: A. carnosus leaves were collected-dried and extracted with water and ethanol by cold maceration with ethanol by soxhlet method. The minimum inhibitory concentration (MIC) of extracts was made and tested against 32 clinical and 1 reference strains of H. pylori. Results: A. carnosus (L.f.) wall inhibited the growth of most of the clinical H. pylori strains. The MIC of A. carnosus (L.f.) wall extracted by cold maceration (aqueous and ethanol) and Soxhlet apparatus (ethanol) ranged from 500 to 62.5 μg/ml, and the majority of the clinical H. pylori strains were inhibited at the MIC of 500 μg/ml of aqueous, ethanol, and Soxhlet ethanol extraction were 63.63%, 43.75%, and 71.87%, respectively.Conclusion: A. carnosus (L.f.) wall is an efficient inhibitor of H. pylori growth in vitro. A. carnosus (L.f.) wall revealed enormous therapeutic potential to H. pylori infection as it was extremely active in the suppression of H. pylori. Hence, it can be taken as a potential agent against several H. pylori linked gastric pathogenic progressions
ANTIMICROBIAL ACTIVITY OF ANISOCHILUS CARNOSUS (L.F.) WALL AGAINST THE HUMAN GASTRIC PATHOGEN HELICOBACTER PYLORI
No full text Objective: The prevalence of Helicobacter pylori in India is high, and majority leads to severe gastrointestinal infections. Existing treatment regimens for H. pylori infections have increased failure rates and adverse side effects that desire the search for an effective substitute therapy. Anisochilus carnosus (L.f.) wall (Lamiaceae), a herb which grows once in a year at high elevation is used widely in traditional treatment for the complaints of gastric ulcer and skin diseases. The present study was performed to assess the antibacterial activity of A. carnosus (L.f.) wall, against clinical isolates of H. pylori in vitro.Methods: A. carnosus leaves were collected-dried and extracted with water and ethanol by cold maceration with ethanol by soxhlet method. The minimum inhibitory concentration (MIC) of extracts was made and tested against 32 clinical and 1 reference strains of H. pylori. Results: A. carnosus (L.f.) wall inhibited the growth of most of the clinical H. pylori strains. The MIC of A. carnosus (L.f.) wall extracted by cold maceration (aqueous and ethanol) and Soxhlet apparatus (ethanol) ranged from 500 to 62.5 μg/ml, and the majority of the clinical H. pylori strains were inhibited at the MIC of 500 μg/ml of aqueous, ethanol, and Soxhlet ethanol extraction were 63.63%, 43.75%, and 71.87%, respectively.Conclusion: A. carnosus (L.f.) wall is an efficient inhibitor of H. pylori growth in vitro. A. carnosus (L.f.) wall revealed enormous therapeutic potential to H. pylori infection as it was extremely active in the suppression of H. pylori. Hence, it can be taken as a potential agent against several H. pylori linked gastric pathogenic progressions.</jats:p
Electromagnetic effects in anti-Hermitian media with gain and loss
No full textFunding Information: L.F. was partly supported by DoinQTech, Jane and Aatos Erkko Foundation. L.F. and M.S.M. thank X. Wang, M. Nyman, and B. Zerulla for their invaluable help with numerical simulations. Also, L.F. wishes to acknowledge the support of Carsten Rockstuhl. Publisher Copyright: © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Incorporating both gain and loss into electromagnetic systems provides possibilities to engineer effects in unprecedented ways. Concerning electromagnetic effects in isotropic media that have concurrently electric and magnetic responses, there is, in fact, a degree of freedom to distribute the gain and loss in different effective material parameters. In this paper, we analytically scrutinize wave interactions with those media, and, most importantly, we contemplate the extreme scenario where such media are anti-Hermitian. Considering various conditions for excitation, polarization, and geometry, we uncover important effects and functionalities such as lasing into both surface waves and propagating waves, conversion of evanescent source fields to transmitted propagating waves, full absorption, and enhancing backward to forward scattering ratio. We hope that these findings explicitly show the potential of anti-Hermiticity to be used in optical physics as well as microwave engineering for creating and using unconventional wave phenomena.Peer reviewe
Recent advances in multi-variate and multi-dimensional analysis of heart rate variability and blood pressure variability
No full textHeart rate variability and blood pressure variability reflected the cardiovascular autonomic nervous system modulation, studies in recent years have been made variable, multi-dimensional, dynamic analysis direction. Heart rate and blood pressure variability in multivariable system identification, time-frequency analysis and nonlinear kinetic analysis, and other technical methods, will be the risk of cardiovascular disease prediction, condition assessment, evaluation and special effects in areas such as the environment more medical applications
Author contributions: L.F
No full textIt is well-known that financial asset returns exhibit fat-tailed distributions and long-term memory. These empirical features are the main objectives of modeling efforts using (i) stochastic processes to quantitatively reproduce these features and (ii) agent-based simulations to understand the underlying microscopic interactions. After reviewing selected empirical and theoretical evidence documenting the behavior of traders, we construct an agent-based model to quantitatively demonstrate that "fat" tails in return distributions arise when traders share similar technical trading strategies and decisions. Extending our behavioral model to a stochastic model, we derive and explain a set of quantitative scaling relations of long-term memory from the empirical behavior of individual market participants. Our analysis provides a behavioral interpretation of the long-term memory of absolute and squared price returns: They are directly linked to the way investors evaluate their investments by applying technical strategies at different investment horizons, and this quantitative relationship is in agreement with empirical findings. Our approach provides a possible behavioral explanation for stochastic models for financial systems in general and provides a method to parameterize such models from market data rather than from statistical fitting. complex systems | power law | scaling laws M odeling price returns has become a central topic in the study of financial markets due to its key role in financial theory and its practical utility. Following models by Engle and Bollerslev (1, 2), many stochastic models have been proposed based on statistical studies of financial data to accurately reproduce price dynamics. In contrast to this stochastic approach, economists and physicists using the tools of statistical mechanics have adopted a bottom-up approach to simulate the same macroscopic regularity of price changes, with a focus on the behavior of individual market participants (3-10). Although the second socalled agent-based approach has provided a qualitative understanding of price mechanisms, it has not yet achieved sufficient quantitative accuracy to be widely accepted by practitioners. Here, we combine the agent-based approach with the stochastic process approach and propose a model based on the empirically proven behavior of individual market participants that quantitatively reproduces fat-tailed return distributions and long-term memory properties (11-14). Empirical and Theoretical Market Behaviors We start by arguing that technical traders (usually agents seeking arbitrage opportunities and make their trading decisions based on price patterns) contribute much more to the dynamics of daily stock prices S t (or log price s t ≡ lnðS t Þ) than fundamentalists (who attempt to determine the fundamental values of stocks). Although fundamentalists hold a majority of the stocks, they trade infrequently (see SI Appendix, Market surveys (16-18) also provide clear evidence of the prevalence of technical analysis. We consider here only technical traders, assuming that fundamentalists contribute only to market noise. Our study is of the empirical data recorded prior to 2006 and ignores the effect of high frequency trading (HFT) that has become significant only in the past 5 y. We propose a behavioral agent-based model that is in agreement with the following empirical evidence: i. Random trading decisions made by agents on a daily basis. n 0 technical traders use different trading strategies, hence their decisions to buy, sell, or hold a position appear to be random. A trading decision is made daily because empirical studies report the lack of intraday trading persistence in empirical trading data (19). Market survey (16) also shows that fund managers put very little emphasis on intraday tradings. We estimate the probability p of having daily trade empirically from trading volumes. ii. Price returns. The price return r t ≡ s t − s t−1 is controlled by the imbalance d t between the demand and the supply of stocks-the difference in the number of buy and sell trades each day. The excess in total demand or supply moves the price up or down, where the largest r t occurs when all traders act in unison, when they all either buy or sell their stocks. We assume this relationship between price change r t and d t to be linear each day, as supported by empirical findings (20, 21). iii. Centralized interaction mechanism of returns on technical strategies. For technical traders, an important input parameter in their strategies is past price movement (22, 23). Consequently, prices and orders reflect a main interaction mechanism between agents. In many agent-based models, the interaction strength between agents need to be adjusted with agent population size (5, 24, 25) or interaction structure (26) to sustain "fat" tails in return distributions. Here we propose a centralized interaction mechanism (price change) among agents so that the strength of interaction grows with agent population and is unaffected by interaction structure. iv. Opinion convergence due to price changes. This is the unique mechanism that distinguishes our model from other models. It specifies the collective behavior of technical traders. Duffy et al. (27) found that agents learn from each other and tend to adopt the strategy that gives the most payoff. Given the price patterns at any point in time, a few most profitable technical strategies dominate the market because every technical trade
Exposé Landwinningsvraagstukken
No full textAls algemeen richtslijn is er aangegeven dat bij de opzet van landwinningswerken rekening gehouden moet worden met een tijdperk van ongeveer 40 jaren. Ten einde een nader inzicht in de voor te bereiden werkzaamheden te bekomen, werd er onderzoek verricht en gedeeltelijk in een viertal nota's vastgelegd. De onderzoeken gaan in specifiek over de 'Beplatingsmethode', waarbij slibvangen en beplanting der slikken een voorname rol spelen en de 'Bekleiingsmethode', waarbij getracht wordt sneller tot het doel te komen door inpoldering van een wadgebied en bekleiing ervan met specie uit de ondergrond. Bij het nagaan der mogelijkheden voor de eerstvolgende 40 jaar wordt gestuit op de volgende 7 hoofdvragen van landbouwkundige aard: 1. Is een proefpolder op de Wadden nodig ten einde te onderzoeken welke mening van slib en wadzand de meest wenselijke is? 2. Kan misschien met goedkopere middelen (proefbakken) worden volstaan? Hoe moeten deze worden ingericht? 3. Is het wadzand geschikt om als weidegrond te kunnen dien? Wat is dan de opbrengst per ha.? 4. Kunnen bossen op het Wadzand worden aangelegd? Welke opbrengst? 5. Wat kan met de zogenaamde woelmachine worden bereikt? Deze machine kan vruchtbare klei tot 4 meter diepte beneden maaiveld ophalen en over de oppervlakte spreiden. Kosten per laag van 4 cm dikte bedragen 300 à 400 gulden. 6. Welke resultaten zijn verkregen bij slibbemseting in Westerwolde en Drente? Een ter plaatse gehouden navraag wees uit dat een laag slib van eenige milimeter dikte na 30 jaar nog steeds opmerkelijk resultaten gaf. 7. Welk kavelgrootte is het meest wenselijk? De viertal nota's betreffen: - Verslag werkzaamheden in 1942 op Hollandsch Diep en Maartensgat (door opzichter Molendijk) - Verslag werkzaamheden in 1942 op de Hellegatplaten (door opzcihter Van Eyk) - Programma van onderzoek betreffende plantenonderzoek (door Dr. L.F. Kamps) - Verslag werkzaamheden proefvelden en plantenonderzoek in 1942 (door assisten Van Eerde)Landwinningswerken 194
Analytical models to assess the potential of waste-based industrial plants in the energy transition: an application to the steelmaking sector
No full textHuman activities, such as fossil fuel combustion and deforestation, have led to increased
greenhouse gas emissions and global warming. To mitigate these effects, countries have
pledged to limit global warming to 1.5°C and achieve carbon neutrality by 2050. This
requires a transition to renewable energy sources, including photovoltaic panels, wind
turbines, hydrogen, and biomethane. While progress has been made in the context of the
energy transition, additional actions are required to reach the goal of reducing greenhouse
gas emissions to net-zero.
The steelmaking sector is particularly challenging to decarbonise due to its reliance on
fossil fuels. However, the so-called secondary route, which involves melting recycled steel
scrap in an electric arc furnace, offers a real decarbonisation potential. This route can be
supported by the production of direct reduced iron, which can be produced using
hydrogen instead of natural gas.
Waste valorisation, which involves converting waste into energy or other valuable
products, can also play a role in the energy transition. Waste valorisation plants can indeed
produce both electricity, hydrogen, and biomethane. However, current waste valorisation
assessment methods lack consideration of their role in the ongoing energy transition.
Consistent with these gaps, the present work aims to develop analytical models to evaluate
waste valorisation plants' economic and environmental performance within the context of
the energy transition.
A cost and investment analysis carried out with respect to three waste-to-energy plants
allowed to identify gasification as the best option to support the current energy transition,
due to its high electricity output despite high operational costs. The application of the
environmental analytical models developed to compare different waste valorisation
alternatives from the anaerobic digestion of waste, showed that biomethane production is
better than electricity production, while hydrogen production is better than biomethane
production. Moreover, the application of an environmental analytical model to the EU
2020 and 2030 scenarios showed that waste-based hydrogen production routes offer
significant decarbonization potential.
An economic model moreover showed that the secondary steelmaking route, supported
by direct reduced iron production, prove to be profitable despite cost and carbon pricing fluctuations. An environmental analytical model allowed to find that national energy mixes
play a crucial role in enabling sector decarbonization. Finally, it was found that waste-based
hydrogen routes can accelerate decarbonization in steelmaking, enabling low-emission
steel production even before large-scale electrolyzer installation becomes viable.
These findings underscore the importance of incorporating energy transition
considerations into waste valorisation assessments to optimize resource utilization and
advance sustainable energy solutions
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