bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation on the effect of hybrid fiber reinforced on the flexural behavior of RC beams having different lap‐spliced lengths
Authors: Turk Kazim , Bassurucu Mahmut 
Published: June 2022

AbstractThere are only a few studies related to the effect of the hybrid fiber reinforcement on the flexural behavior of full‐scale beam specimens having lap‐spliced length. Thus, this study will ensure important experimental data about the effect of macro steel fibers blended with micro steel fibers on lap‐spliced length. The aim of this study was to investigate the influence of hybrid steel fiber reinforcement on the flexural behavior of full‐scale reinforced concrete beams having different lap‐spliced bars. A sum of three traditional concrete mixtures including a total of 1% fiber by volume fraction was adopted: control mixture without steel fiber, only macro steel fiber and hybrid steel fiber reinforced mixtures. For this purpose, 18 full‐scale beams (200 × 300 × 2000 mm) having three different lap‐spliced length (15, 25, and 35Ø) as tension steel bars were produced and tested under four‐point bending to examine flexural behavior, mode of failure, ductility, and energy absorption capacity properties. In conclusion, the hybrid fiber reinforcement caused the highest increase in the load carrying capacity of the beam specimens. Besides, the hybrid fiber reinforced beam specimens exhibited excellent ductility and energy absorption capacity compared to single fiber reinforced beam specimens. On the other hand, it can be addressed that the hybrid fiber reinforced structural elements had a vital important to compensate the application errors and carelessness in steel bar workmanship, inadequate the lap‐spliced length as per the codes. It can be emphasized that the lap‐spliced length as per the building codes can be reduced in 40% by containing hybrid steel fiber (0.8% macro‐0.2% micro) reinforced concrete without a reduction in load carrying capacity, ductility, and energy absorption capacity compared to control beam specimens without fiber.
Efficiency improvement of Roots vacuum pump working process
Authors: Burmistrov Aleksey , Raykov Alexey , Isaev Aleksandr , Salikeev Sergey , Kapustin E. , Fomina Marina 
Published: June 2022

SummaryIn this paper influence of rotor profile type of Roots vacuum pumps on backward leakage through channels of rotor mechanism and pumping speed is considered.Elliptical, involute, and circular profiles are widely used. Backward leakage through channels of rotor mechanism with different rotor profiles is determined from conductance which was calculated by angular coefficients method for free molecular flow regime at different rotors rotating angles. It is shown that backward leakage is maximal at rotors rotating angles 25–45° due to maximal inter‐rotor channel opening for gas flow and is minimal at 0°. Elliptical rotor profile provides minimal backward leakage over one revolution.Numerical modeling of Roots pump working process was carried out on the basis of CFD ANSYS‐CFX complex by dynamic meshing method. SST turbulence model was used for calculations. It is confirmed that maximal pumping speed is provided by Roots pump with elliptical rotor profile.
Validation of near‐shore wind measurements using a dual scanning light detection and ranging system
Authors: Shimada Susumu , Kogaki Tetsuya , Konagaya Mizuki , Mito Toshinari , Araki Ryuzou , Ueda Yuko , Ohsawa Teruo 
Published: June 2022

AbstractThis paper reports results from a 2‐month validation campaign of near‐shore wind measurements taken by a dual scanning light detection and ranging (LiDAR) system at a coastal site in Japan. A meteorological mast and a vertical profiling LiDAR device were deployed at an offshore research station approximately 1.5 km from the coast. Offshore winds at heights of 66, 120, and 180 m above sea level were observed by the scanning LiDAR system. Comparisons with a sonic anemometer found that the radial velocities had a coefficient of determination of more than 0.99 without unreasonable bias. The accuracy of 10‐min mean wind speeds and directions was then evaluated. The 10‐min values from the dual scanning LiDAR system were accurate enough to satisfy the acceptance criteria used for floating LiDAR systems. In addition, the vertical velocity and direction profiles from the dual scanning LiDAR system were compared with those from a vertical profiling LiDAR device. The performance of turbulence intensity (TI) measurements was also evaluated. Although the TIs from the dual scanning LiDAR system were slightly lower than those from the sonic anemometer, they were equivalent to those from the cup anemometers. This investigation concluded that the near‐shore wind measurements using the dual scanning LiDAR system are beneficial for reducing near‐shore wind measurement costs, because the system can measure not only 10‐min wind speed and direction, but also parameters associated with assessing site‐specific conditions without installing offshore meteorological masts.
Nitrogen Isotopes in Tree Rings—Challenges and Prospects
Authors: Savard Martine M. , Siegwolf Rolf T. W. 
Published: June 2022

AbstractNutritive, but detrimental if at high levels, several nitrogen (N) forms involved in air and soil biogeochemical reactions constitute the N load trees assimilate. Although a large body of literature describes series of tree-ring N isotopes (δ15N) as archival systems for environmental changes, several questions relative to the isotopic integrity and reproducibility of trends still linger in the dendroisotopist community. This chapter reviews the fundamentals of forest N cycling and examines trees as N receptors in their very position, at the interface between the atmosphere and pedosphere. The related scrutiny of intrinsic and extrinsic mechanisms regulating isotopic changes also underlines flaws and forces of tree-ring δ15N series as environmental indicators.
Postphotosynthetic Fractionation in Leaves, Phloem and Stem
Authors: Gessler Arthur , Ferrio Juan Pedro 
Published: June 2022

AbstractStable carbon isotope ratios (δ13C) in organic matter convey important integrated and (if assessed in the tree ring archive) dateable information on plant physiology and related environmental drivers. While the generation of the δ13C signal in the primary assimilates in the leaves via photosynthetic carbon isotope fractionation is well understood, we still lack detailed knowledge of the processes that determine the isotopic fractionation in downstream processes in the leaves and during the transport in the stem, which in turn affect δ13C in the tree-ring archive. We here provide an update on processes that drive post-carboxylationcarbon isotope fractionation in the leaves, on potential changes in δ13C related to phloem loading and transport and we also discuss the role of stem CO2 fluxes (bark photosynthesis, stem respiration and CO2 fixation by phosphoenol pyruvate carboxylase). Moreover, we address the impact of carbon storage and remobilization on the intra-annual variation of δ13C in tree rings. Finally, we point to the potential importance of the intra-molecularcarbon isotope distribution in carbohydrates for tree ring δ13C and its relation to shifts in metabolic pathways.
Limits and Strengths of Tree-Ring Stable Isotopes
Authors: Andreu-Hayles Laia , Lévesque Mathieu , Guerrieri Rossella , Siegwolf Rolf T. W. , Körner Christian 
Published: June 2022

AbstractThis chapter aims at summarizing strengths and caveats on the suitability of stable carbon and oxygen isotopes in tree rings as recorders for fingerprints of environmental influences. First, environmental constraints limiting tree growth and shaping tree species distribution worldwide are discussed. Second, examples are presented for environmental conditions under which tree-ring isotopes record environmental signals particularly well, but also cases where physiological processes can mask climate signals. Third, the link between leaf-level carbon assimilation and the investment of assimilates in the stem during the annual ring formation are discussed in light of the resulting deviations of the isotopic values between leaves and tree rings. Finally, difficulties and pitfalls in the interpretation of stable isotope signals in tree rings are reviewed. These problems often result from a poor understanding of when and how the tree canopy, stems and roots are physiologically interconnected. Current literature suggests that photosynthesis and radial growth are only loosely coupled, if at all, challenging the interpretation of environmental signals recorded in tree-ring isotopes. Harsh environmental conditions (e.g. low temperatures, drought) often result in a decoupling of carbon assimilation and growth. The chapter closes by providing possible solutions on how to improve the detection of environmental information from stable isotope signals by integrating scales and different methodological approaches.
Post-photosynthetic Carbon, Oxygen and Hydrogen Isotope Signal Transfer to Tree Rings—How Timing of Cell Formations and Turnover of Stored Carbohydrates Affect Intra-annual Isotope Variations
Authors: Kagawa Akira , Battipaglia Giovanna 
Published: June 2022

AbstractIn this chapter, we discuss post-photosynthetic processes that affect intra-annual variation in the stable isotopes of tree rings, such as timing of cell formations and turnover of stored carbohydrates, by combining research findings gained by using either natural-abundance or artificially-enriched carbon, oxygenand hydrogen isotopes. We focus on within-ring variation in stable isotope ratios, with an emphasis on aligning observed ratios in whole wood or extracted cellulose to seasonal dynamics in climate and phenology. We also present a discussion of isotopic fractionation that operates within the scope of observed variations across individual rings. We then introduce a model that traces the seasonal partitioning of photosynthate into tree rings via storage pool, which is based on experimental data gained from labeling studies using artificially enriched 13CO2 gas. Finally, we will describe our current understanding of post-photosynthetic signal transfer processes of oxygenand hydrogen isotopes from leaves to tree rings, such as exchange of oxygen and hydrogen between storage carbohydrates and local cambial water, and possible causes of difference in oxygen and hydrogen isotope fractionations. Finally, we discuss mechanisms behind how oxygen and hydrogen from foliar-absorbed liquid water is then incorporated into wood biomass, by introducing results gained from recent H218O and HDO pulse-labeling experiments.
Probing Tree Physiology Using the Dual-Isotope Approach
Authors: Roden John , Saurer Matthias , Siegwolf Rolf T. W. 
Published: June 2022

AbstractThe environmental and physiological interpretation of stable isotope variation in organic matter is affected by many different and interacting factors. This is especially true when considering isotope variation in tree rings, which are influenced not only by leaf-level photosynthetic gas exchange processes but also by post-photosynthetic fractionation. It has been proposed that measuring multiple isotopes on the same sample may constrain such interpretations if one isotope provides independent information about important fractionation events that cause variation in another isotope. Here we describe one such “dual-isotope approach” where oxygen isotope variation (δ18O) is used to probe the effects of stomatal conductance on carbon isotope (δ13C) variation for the same sample. This chapter describes the development of this conceptual model, constraints on model applicability, particularly with respect to tree rings, and how it has been utilized to explore aspects of tree physiology.
Intrinsic Water-Use Efficiency Derived from Stable Carbon Isotopes of Tree-Rings
Authors: Saurer Matthias , Voelker Steve 
Published: June 2022

AbstractStable carbon isotopes in tree-rings are not only useful to derive climatic information of the past. Based on the isotope fractionations during uptake and fixation of CO2, physiological information can be retrieved, namely the ratio of assimilation to stomatal conductance, which is termed the intrinsic water-use efficiency (iWUE). This crucial plant physiological trait varies among species and environments and is characteristic of how much water is lost from leaves for a certain carbon gain. iWUE is of great importance at the scale of individual plants because it can determine plant performance and survival. iWUE also contributes how closely canopy- or ecosystem-scale carbon and water fluxes are coupled or divergent, which has implications for understanding biogeochemical cycling. Carbon isotopes in tree-rings can be used to estimate how iWUE of trees has changed in the past, e.g. due to increasing CO2, nitrogen or other factors. Accordingly, many applications have explored this tool for various forest ecosystems across the globe, often reporting a strong increase in iWUE over the twentieth century. Explicit comparisons of tree-ring iWUE to growth-data obtained from the same rings can help distinguish among strategies plants employ under various environmental impacts, like increasing CO2, light limitation, drought or too much water. In this chapter, we describe the theory behind iWUE, show some limitations of the method, give examples of the combined application of iWUE and tree-ring width, discuss photosynthetic limitations of iWUE and finally show how the method has been applied in large-scale tree-ring networks.
Spatial and Temporal Variations in Plant Source Water: O and H Isotope Ratios from Precipitation to Xylem Water
Authors: Allen Scott T. , Sprenger Matthias , Bowen Gabriel J. , Brooks J. Renée 
Published: June 2022

AbstractThe water present within trees when sugars and cellulose are formed is the source of hydrogen and oxygen atoms that are incorporated into tree-ring cellulose (see Chaps. 10.1007/978-3-030-92698-4_10 and 10.1007/978-3-030-92698-4_11). However, the isotope composition of relevant water pools is often unknown when trying to interpret δ18O and δ2H isotopic records in tree rings. This chapter focuses on the factors that can influence the O and H isotope ratios of source waters for trees. Trees generally use water that originated as precipitation, but this does not mean that the isotope ratios of water used by trees—predominantly taken up by roots from soils—and incorporated in cellulose exactly matches precipitation isotope ratios. Precipitation isotope ratios vary in space and time, and only a fraction of all precipitation infiltrates soils, reaches roots, and is ultimately taken up by trees. Considering species, soils, and climates may allow for predicting which fraction of water resides in the root-zone during the growing seasons, and how its isotope ratios deviate from that of average precipitation. Here we provide an overview of the terrestrial water cycle and the associated transport and fractionation processes that influence the stable isotope ratios of water used by trees. We highlight obstacles and opportunities to be considered, towards more accurately interpreting the records of O and H isotope ratios in tree cellulose.
Stable Isotopes in Tree Rings of Tropical Forests
Authors: van der Sleen Peter , Zuidema Pieter A. , Pons Thijs L. 
Published: June 2022

AbstractThe study of stable isotopes in tree rings is relatively new, but growing research field in tropical forests. In this chapter, we review 53 studies that measured stable isotopes of C, O and/or N in tree rings of a total of 83 tropical tree species. Tree growth in tropical forests is generally determined by seasonality of precipitation, and not temperature. Consequently, temporal variation in both δ13C and δ18O has often been correlated to precipitation and variability of the El Niño Southern Oscillation (ENSO), which can affect weather systems throughout the tropics and subtropics. Currently, stable isotopes research in the tropics has mainly focused on (i) quantifying the effects of rising atmospheric CO2 concentration and climate change on tree physiology, (ii) identifying the drivers of growth variability and reconstruction of past climate, and (iii) the identification of annual rings in wood lacking anatomically distinct growth boundaries. In addition, some initial studies used tree-ring δ15N as a tool to assess anthropogenic change of the nitrogen cycle in tropical forests. Although stable isotope analyses in the tropics still faces methodological and interpretation issues, it is becoming an important tool for understanding the functioning of tropical forests and their resilience to global change.
Sample Collection and Preparation for Annual and Intra-annual Tree-Ring Isotope Chronologies
Authors: Belmecheri Soumaya , Wright William E. , Szejner Paul 
Published: June 2022

AbstractThis chapter provides guidance for conducting studies based on stable isotope measurements in tree rings to infer past and present climate variability and ecophysiology. Balancing theoretical perspectives of stable isotope variations recorded in tree rings, intended research applications (paleoclimate or ecophysiology) and resource limitations, this chapter describes key aspects of field sampling strategies and laboratory sample processing. It presents an overview of factors influencing variations and thus interpretations of carbon and oxygen isotopes, including juvenile/age effects, canopy status and stand characteristicsto inform sampling strategies that optimize a robust paleoenvironmental and physiological signal with statistically defined confidence limits. Fieldwork considerations include the selection of a study site and trees, field equipment, and sample requirements to recover sufficient material for isotopic measurements, and the desired environmental signal. Aspects of laboratory sample processing include choosing a sampling resolution (e.g. whole ring, earlywood/latewood, thin section, etc.), sample pooling within and between trees, and particle size requirements for chemical extraction and analytical repeatability. Finally, this chapter provides a case study highlighting the potential benefits and limitations of high-resolution sub-seasonal sampling.
Newer Developments in Tree-Ring Stable Isotope Methods
Authors: Rinne-Garmston Katja T. , Helle Gerhard , Lehmann Marco M. , Sahlstedt Elina , Schleucher Jürgen , Waterhouse John S. 
Published: June 2022

AbstractThe tree-ring stable C, O and H isotope compositions have proven valuable for examining past changes in the environment and predicting forest responses to environmental change. However, we have not yet recovered the full potential of this archive, partly due to a lack understanding of fractionation processes resulting from methodological constraints. With better understanding of the biochemical and tree physiological processes that lead to differences between the isotopic compositions of primary photosynthates and the isotopic compositions of substrates deposited in stem xylem, more reliable and accurate reconstructions could be obtained. Furthermore, by extending isotopic analysis of tree-ring cellulose to intra-molecular level, more information could be obtained on changing climate, tree metabolism or ecophysiology. This chapter presents newer methods in isotope research that have become available or show high future potential for fully utilising the wealth of information available in tree-rings. These include compound-specific analysis of sugars and cyclitols, high spatial resolution analysis of tree rings with UV-laser, and position-specific isotope analysis of cellulose. The aim is to provide the reader with understanding of the advantages and of the current challenges connected with the use of these methods for stable isotope tree-ring research.
Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii)
Authors: Péter Hella , Zuberbühler Klaus , Hobaiter Catherine 
Published: June 2022

AbstractAccess to resources shapes species’ physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees (Pan troglodytes schweinfurthii) and suggest that it may have been imported into the community’s behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.
Effects of tropical forest conversion into oil palm plantations on nitrous oxide emissions: A meta-analysis
Authors: Mori Taiki 
Published: June 2022

AbstractOil palm plantations have dramatically expanded in tropical Asia over the past decades. Although their establishment has been projected to increase nitrous oxide (N2O) emissions, earlier reports have shown inconsistent results. This study analyzed these previously published data to compare N2O emissions in oil palm plantations to reference forests. A linear mixed-effects model was used to examine the significance of the effect of establishing oil palm plantations on N2O emissions, rather than to calculate mean effect sizes because of limitations in the data structure. The results indicated that N2O emissions were significantly greater from oil palm plantations than from reference forests, as expected. This is the first study to report the effect of oil palm plantations on N2O emissions by synthesizing previously published data. To quantify the size of this effect, additional studies with frequent and long-term monitoring data are needed.