Consequences Of Variation Research Articles

Reproductive strategies and their consequences for divergence, gene flow, and genetic diversity in three taxa of Clarkia.

Differences in reproductive strategies can have important implications for macro- and micro-evolutionary processes. We used a comparative approach through a population genetics lens to evaluate how three distinct reproductive strategies shape patterns of divergence among as well as gene flow and genetic diversity within three closely related taxa in the genus Clarkia. One taxon is a predominantly autonomous self-fertilizer and the other two taxa are predominantly outcrossing but vary in the primary pollinator they attract. In genotyping populations using genotyping-by-sequencing and comparing loci shared across taxa, our results suggest that differences in reproductive strategies in part promote evolutionary divergence among these closely related taxa. Contrary to expectations, we found that the selfing taxon had the highest levels of heterozygosity but a low rate of polymorphism. The high levels of fixed heterozygosity for a subset of loci suggests this pattern is driven by the presence of structural rearrangements in chromosomes common in other Clarkia taxa. In evaluating patterns within taxa, we found a complex interplay between reproductive strategy and geographic distribution. Differences in the mobility of primary pollinators did not translate to a difference in rates of genetic diversity and gene flow within taxa - a pattern likely due to one taxon having a patchier distribution and a less temporally and spatially reliable pollinator. Taken together, this work advances our understanding of the factors that shape gene flow and the distribution of genetic diversity within and among closely related taxa.

Intelligent Power Control of Inverter Air Conditioners in Power Systems: A Brain Emotional Learning-Based Approach

Inverter air-conditioning (IAC) units have been proved to be effective in frequency regulation by providing flexible capacities. This paper proposes a brain emotional learning (BEL)-based controller to provide the IACs with control signals to be efficiently involved in the frequency regulation in power systems. The BEL-based controller can learn quick-auto, making it appropriate in systems facing uncertainty. To assess the BEL controller performance in realistic conditions, the uncertainties as a consequence of variations in system parameters and load level are considered. The goal is to use the BEL controller to increase the IAC units' ability to track regulation signals accurately in uncertain circumstances. The controller is compared to a fuzzy-PI control, a proportional control scheme, a model predictive control and a linear quadratic regulator control. A delay-dependent stability criterion is used to calculate the highest time delay in the IACs response under which the system maintains stability. In addition, this paper presents an BEL-based coordinator to coordinate the IACs and traditional generation units for compensating considerable frequency variations caused by the time delays. Case studies are accomplished on a multi-area power system in MATLAB/Simulink environment. Eventually, real-time verifications by OPAL-RT real-time digital simulator on the simulated power system are executed to assess the control method.

GaSb/GaAs Type‐II heterojunction GAA‐TFET with core source for enhanced analog/RF performance and reliability

AbstractFor the first time, a novel source extension heterojunction gate‐all‐around tunnel FET (SE‐GAA‐TFET) is proposed and examined using Synopsys TCAD simulator in this manuscript. SE‐GAA‐TFET is found to exhibit improved performance in terms of various analog/RF and DC parameters. As channel/source (C/S) interface and electric field exerted by gate are perpendicular to each other, radius of channel is downscaled to enhance electric filed, without reducing area of the tunneling. Furthermore, the presence of GaSb/GaAs heterojunction at C/S interface leads to reduction in the effective band overlap, which helps a great number of mobile charges to tunnel through C/S boundary at ON‐state. The consequences of variation in different geometrical metrics are evaluated to optimize the device performance. SE‐GAA‐TFET is found to offer a current switching ratio (CSR) of ~1013 along with 32.2 mV dec−1 of average sub‐threshold swing (SSAVG). Furthermore, improvement in transconductance and parasitic capacitance boost the cut‐off frequency of SE‐GAA‐TFET up to 37 GHz. Next, both positive and negative traps are introduced at S/C interface and the study reveals that there is no much deviation in parameters of the transfer characteristics like ION, SSAVG, and IOFF of SE‐GAA‐TFET. Next, proper benchmarking is done to compare the performance of the SE‐GAA‐TFET with similar devices available in literature and it is found that proposed SE‐GAA‐TFET exhibits better DC performance due to improved electrostatic behavior. Finally, SE‐GAA‐TFET is found to offer better fall time along with full‐voltage swing when deployed in a resistive load inverter.

Variability in Plant–Herbivore Interactions

Plants and herbivores are remarkably variable in space and time, and variability has been considered a defining feature of their interactions. Empirical research, however, has traditionally focused on understanding differences in means and overlooked the theoretically significant ecological and evolutionary roles of variability itself. We review the literature with the goal of showing how variability-explicit research expands our perspective on plant–herbivore ecology and evolution. We first clarify terminology for describing variation and then review patterns, causes, and consequences of variation in herbivory across scales of space, time, and biological organization. We consider how incorporating variability improves existing hypotheses and leads to new ones. We conclude by suggesting future work that reports full distributions, integrates effects of variation across scales, describes nonlinearities, and considers how stochastic and deterministic variation combine to determine herbivory distributions.

The association between type of conception through medically assisted reproduction and childhood cognition: a Danish population-wide cohort study.

Previous research has indicated that children conceived through medically assisted reproduction (MAR) generally have cognitive outcomes comparable to or better than naturally conceived children. However, previous studies have been limited in their ability to examine this relationship at a population level and consider variations across different types of MAR. This study utilizes data from all live births in Denmark between 2006 and 2009 (n = 259 608), including a subset of births resulting from MAR conceptions (n = 13 566). The dependent variable is the standardized test scores obtained in the second and third grades of primary schools. A comparison is made between the test scores of children spontaneously conceived (SC) and those conceived through intrauterine insemination (IUI) and assisted reproductive technologies (ART). Ordinary least squares regressions are employed, with a baseline model adjusted only for birth year, as well as models that additionally account for conception-related confounders and sociodemographic family characteristics. In the baseline analysis, ART- and IUI-conceived children displayed better test scores compared with their SC peers. However, after adjusting for relevant factors, ART-conceived children performed worse than SC peers, while IUI-conceived children performed equally well as SC peers and better than ART-conceived children. These results likely reflect differences in the selection process of potential parents into the type of MAR, as well as the consequences of variations in fecundability. Nevertheless, the differences observed across conception types were overshadowed by test score disparities in socioeconomic background.

Consequences of polyploidy and divergence as revealed by cytogenetic mapping of tandem repeats in African clawed frogs (Xenopus, Pipidae)

Repetitive elements have been identified in several amphibian genomes using whole genome sequencing, but few studies have used cytogenetic mapping to visualize these elements in this vertebrate group. Here, we used fluorescence in situ hybridization and genomic data to map the U1 and U2 small nuclear RNAs and histone H3 in six species of African clawed frog (genus Xenopus), including, from subgenus Silurana, the diploid Xenopus tropicalis and its close allotetraploid relative X. calcaratus and, from subgenus Xenopus, the allotetraploid species X. pygmaeus, X. allofraseri, X. laevis, and X. muelleri. Results allowed us to qualitatively evaluate the relative roles of polyploidization and divergence in the evolution of repetitive elements because our focal species include allotetraploid species derived from two independent polyploidization events — one that is relatively young that gave rise to X. calcaratus and another that is older that gave rise to the other (older) allotetraploids. Our results demonstrated conserved loci number and position of signals in the species from subgenus Silurana; allotetraploid X. calcaratus has twice as many signals as diploid X. tropicalis. However, the content of repeats varied among the other allotetraploid species. We detected almost same number of signals in X. muelleri as in X. calcaratus and same number of signals in X. pygmaeus, X. allofraseri, X. laevis as in the diploid X. tropicalis. Overall, these results are consistent with the proposal that allopolyploidization duplicated these tandem repeats and that variation in their copy number was accumulated over time through reduction and expansion in a subset of the older allopolyploids.

What Darwin could not see: island formation and historical sea levels shape genetic divergence and island biogeography in a coastal marine species

Oceanic islands play a central role in the study of evolution and island biogeography. The Galapagos Islands are one of the most studied oceanic archipelagos but research has almost exclusively focused on terrestrial organisms compared to marine species. Here we used the Galapagos bullhead shark (Heterodontus quoyi) and single nucleotide polymorphisms (SNPs) to examine evolutionary processes and their consequences for genetic divergence and island biogeography in a shallow-water marine species without larval dispersal. The sequential separation of individual islands from a central island cluster gradually established different ocean depths between islands that pose barriers to dispersal in H. quoyi. Isolation by resistance analysis suggested that ocean bathymetry and historical sea level fluctuations modified genetic connectivity. These processes resulted in at least three genetic clusters that exhibit low genetic diversity and effective population sizes that scale with island size and the level of geographic isolation. Our results exemplify that island formation and climatic cycles shape genetic divergence and biogeography of coastal marine organisms with limited dispersal comparable to terrestrial taxa. Because similar scenarios exist in oceanic islands around the globe our research provides a new perspective on marine evolution and biogeography with implications for the conservation of island biodiversity.

Self-regulation of peer feedback quality aspects through different dimensions of experience within prior peer feedback assignments

Although peer review is a widely-used pedagogical technique, its value depends upon the quality of the reviews that students produce, and much research remains to be done to systematically study the nature, causes, and consequences of variation in peer review quality. We propose a new framework that conceptualizes five larger dimensions of peer review quality and then present a study that investigated three specific peer review quality constructs in a large dataset and further explored how these constructs change through different types of self-regulation peer reviewing experiences. Peer review data across multiple assignments were analyzed from 2,092 undergraduate students enrolled in one of three offerings of a biology course at a large public research university in the United States. Peer review quality was measured in terms of comment amount, comment accuracy, and rating accuracy; the measures of reviewing experience focused upon self-regulated learning factors such as practice, feedback, others’ modeling, and relative performance. Meta-correlation (for testing reliability, separability, and stability) and meta-regression (as a time-series analysis for testing the relationship of changes across assignments in reviewing quality with experiences as reviewer and reviewee) are used to establish the robustness of effects and meaningful variation of effects across course offerings and assignments. Results showed that there were three meaningful review quality constructs (i.e., were measured reliably, separable, and semi-stable over time). Further, all three showed changes in response to previous reviewer and reviewee experiences, but only feedback helpfulness, in particular, showed effects of all four examined types of self-regluation experiences (practice, feedback, others’ modeling, and relative performance). The findings suggest that instructors can improve review quality by providing comment prompt scaffolds that lead to longer comments as well as by matching authors with similarly performing reviewers.

Cylindrical void growth vs. grain fragmentation in FCC single crystals: CPFEM study for two types of loading conditions

The crystal plasticity finite element method (CPFEM) is used to investigate the coupling between the cylindrical void growth or collapse and grain refinement in face-centred cubic (FCC) single crystals. A 2D plane strain model with one void is used. The effect of the initial lattice orientation, similarities, and differences between stress- and strain-driven loading scenarios are explored. To this end, boundary conditions are enforced in two different ways. The first one is based on maintaining constant in-plane stress biaxiality via a dedicated truss element, while the second one is imposing a constant displacement biaxiality factor. Uniaxial and biaxial loading cases are studied. For the uniaxial loading case a special configuration, which enforces an equivalent pattern of plastic deformation in the pristine crystal, is selected in order to investigate the mutual interactions between the evolving void and the developed lattice rotation heterogeneity. Next, biaxial loading cases are considered for three crystal orientations, one of which is not symmetric with respect to loading directions. It is analysed how stress or strain biaxility factors and initial lattice orientation influence the void evolution in terms of its size and shape. Moreover, the consequences of variations in the resulting heterogeneity of lattice rotation are studied in the context of the grain refinement phenomenon accompanying the void evolution. Scenarios that may lead to more advanced grain fragmentation are identified.

Evolutionary Quantitative Proteomics of Reproductive Protein Divergence in Drosophila

Reproductive traits often evolve rapidly between species. Understanding the causes and consequences of this rapid divergence requires characterization of female and male reproductive proteins and their effect on fertilization success. Species in the Drosophila virilis clade exhibit rampant interspecific reproductive incompatibilities, making them ideal for studies on diversification of reproductive proteins and their role in speciation. Importantly, the role of intraejaculate protein abundance and allocation in interspecific divergence is poorly understood. Here, we identify and quantify the transferred male ejaculate proteome using multiplexed isobaric labeling of the lower female reproductive tract before and immediately after mating using three species of the virilis group. We identified over 200 putative male ejaculate proteins, many of which show differential abundance between species, suggesting that males transfer a species-specific allocation of seminal fluid proteins during copulation. We also identified over 2000 female reproductive proteins, which contain female-specific serine-type endopeptidases that showed differential abundance between species and elevated rates of molecular evolution, similar to that of some male seminal fluid proteins. Our findings suggest that reproductive protein divergence can also manifest in terms of species-specific protein abundance patterns.

Evolutionary Consequences of Functional and Regulatory Divergence of HD-Zip I Transcription Factors as a Source of Diversity in Protein Interaction Networks in Plants.

The HD superfamily has been studied in detail for several decades. The plant-specific HD-Zip I subfamily attracts the most attention because of its involvement in plant development and stress responses. In this review, we provide a comprehensive insight into the evolutionary events responsible for the functional redundancy and diversification of the HD-Zip I genes in regulating various biological processes. We summarized the evolutionary history of the HD-Zip family, highlighting the important role of WGDs in its expansion and divergence of retained duplicates in the genome. To determine the relationship between the evolutionary origin and functional conservation of HD-Zip I in different species, we performed a phylogenetic analysis, compared their expression profiles in different tissues and under stress and traced the role of orthologs and paralogs in regulating developmental processes. We found that HD-Zip I from different species have similar gene structures with a highly conserved HD and Zip, bind to the same DNA sequences and are involved in similar biological processes. However, they exhibit a functional diversity, which is manifested in altered expression patterns. Some of them are involved in the regulation of species-specific leaf morphology and phenotypes. Here, we discuss the role of changes in functional domains involved in DNA binding and protein interaction of HD-Zip I and in cis-regulated regions of its target genes in promoting adaptive innovations through the formation of de novo regulatory systems. Understanding the role of the HD-Zip I subfamily in organism-environment interactions remains a challenge for evolutionary developmental biology (evo-devo).

Surface Deposition Induced Reduction of the Ground State Spin in Cr10 Wheel

AbstractWe report the deposition of monolayers and multilayers of {Cr10(OMe)20(O2CCMe3)10} wheels, hereafter {Cr10}, onto Au(111) and Cu(111) single‐crystal substrates, and their characterization combining scanning tunneling microscopy, X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, X‐ray natural linear dichroism, and X‐ray magnetic circular dichroism (XMCD). {Cr10} in bulk shows axial magnetic anisotropy and a cluster total spin S = 9 ground state, stemming from an interaction scheme of two semi‐crowns containing four Cr3+ ions interacting ferromagnetically, separated by two Cr3+ antiferromagnetically coupled. The one‐monolayer (1ML) samples of {Cr10} sublimated on Ag(111) and Cu(111) show slightly different applied magnetic field dependence of XMCD signal. The field‐dependence of the magnetization evolves from a lower curve for the 1ML {Cr10} samples to a curve resembling the bulk one as the number of layers is increased, as shown in a 14ML sample. Monte Carlo simulations allow rationalizing the magnetization curves of the 1ML samples in terms of a reduction of the cluster ground‐state total spin, S = 3 or S = 6, as a consequence of variations in the intra‐wheel coupling interactions induced by the on‐surface deposition. The sensitivity of the magnetic configuration of {Cr10} to minor distortions of the intramolecular conformation might be exploited to control magnetism by external stimuli for applications.

Human scalp hair as a thermoregulatory adaptation

Humans are unique among mammals in having a functionally naked body with a hair-covered scalp. Scalp hair is exceptionally variable across populations within Homo sapiens. Neither the function of human scalp hair nor the consequences of variation in its morphology have been studied within an evolutionary framework. A thermoregulatory role for human scalp hair has been previously suggested. Here, we present experimental evidence on the potential evolutionary function of human scalp hair and variation in its morphology. Using a thermal manikin and human hair wigs at different wind speeds in a temperature and humidity-controlled environment, with and without simulated solar radiation, we collected data on the convective, radiative, and evaporative heat fluxes to and from the scalp in relation to properties of a range of hair morphologies, as well as a naked scalp. We find evidence for a significant reduction in solar radiation influx to the scalp in the presence of hair. Maximal evaporative heat loss potential from the scalp is reduced by the presence of hair, but the amount of sweat required on the scalp to balance the incoming solar heat (i.e., zero heat gain) is reduced in the presence of hair. Particularly, we find that hair that is more tightly curled offers increased protection against heat gain from solar radiation.

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Effects of Individualism, Collectivism, Materialism, and Willingness to Pay for Environmental Protection on Environmental Consciousness and Pro-Environmental Consumption Behavior in Korea

Environmental consciousness is linked to pro-environmental consumption behavior; however, the consequences of variations in the level of environmental consciousness have not been fully investigated. Therefore, we evaluated differences in individualism, collectivism, materialism, willingness to pay (WTP) for environmental protection, and pro-environmental consumption between groups with varying levels of environmental consciousness. After evaluating the factors that differentiate these groups, we identified the determinants of pro-environmental consumption for each group. For the study, an online survey was conducted, including 472 adults aged 20–69 years. Groups with low and high levels of environmental consciousness differed significantly with respect to all factors except individualism. The group with a high environmental consciousness exhibited higher collectivism, WTP for environmental protection, and pro-environmental consumption behavior, and lower materialism than the group with a low environmental consciousness. For the group with low environmental consciousness, collectivism was the main factor affecting pro-environmental consumption behavior (i.e., purchase, use, and disposal). In the group with high environmental consciousness, WTP for environmental protection and collectivism were the main determinants of pro-environmental consumption behavior. These results provide a basis for a systematic approach to improve pro-environmental consumption behavior based on environmental consciousness.

Grado motivacional del docente salesiano para el abordaje sanitario ante el desabastecimiento hídrico en Huancayo, 2021

Access to water and sanitation services is a very important factor in the control and elimination of diseases, water scarcity can be a social construction or a consequence of variation, such as climate change, therefore, it is necessary to implement strategies that Provide tools to citizens to mitigate this problem. In this sense, an educational strategy was designed to address water deficiency in Huancayo, from which the motivational degree of Salesian teachers was assessed. An investigation was carried out from the participatory diagnostic method, the vulnerability of knowledge was estimated and areas based on scientific documentation were established to direct the approach strategies. Subsequently, the motivational degree of teachers was specified, obtaining a higher motivational degree for interventions related to personal, domestic and food hygiene, and less motivation for responsible pet ownership and vector control. It is inferred that it is necessary to strengthen the capacities in these areas of knowledge, so that in this way the health approach is effective and efficient, this starting from the fact that motivation is the engine that can promote other skills and urge behavioral changes necessary to reduce the burden of diseases associated with water deficiency.

Integrating neuroplasticity and evolution

Neuroplasticity and evolutionary biology have been prominent fields of study for well over a century. However, they have advanced largely independently, without consideration of the benefits of integration. We propose a new framework by which researchers can begin to examine the evolutionary causes and consequences of neuroplasticity. Neuroplasticity can be defined as changes to the structure, function or connections of the nervous system in response to individual experience. Evolution can alter levels of neuroplasticity if there is variation in neuroplasticity traits within and between populations. Neuroplasticity may be favored or disfavored by natural selection depending on the variability of the environment and the costs of neuroplasticity. Additionally, neuroplasticity may affect rates of genetic evolution in many ways: for example, decreasing rates of evolution by buffering against selection or increasing them via the Baldwin effect, by increasing genetic variation or by incorporating evolved peripheral changes to the nervous system. These mechanisms can be tested using comparative and experimental approaches and by examining patterns and consequences of variation in neuroplasticity among species, populations and individuals.

Plasticity and repeatability in spring migration and parturition dates with implications for annual reproductive success.

In seasonal environments, animals should be adapted to match important life-history traits to when environmental conditions are optimal. Most animal populations therefore reproduce when resource abundance is highest to increase annual reproductive success. When facing variable, and changing, environments animals can display behavioural plasticity to acclimate to changing conditions. Behaviours can further be repeatable. For example, timing of behaviours and life history traits such as timing of reproduction may indicate phenotypic variation. Such variation may buffer animal populations against the consequences of variation and change. Our goal was to quantify plasticity and repeatability in migration and parturition timing in response to timing of snowmelt and green-up in a migratory herbivore (caribou, Rangifer tarandus, n=132 ID-years) and their effect on reproductive success. We used behavioural reaction norms to quantify repeatability in timing of migration and timing of parturition in caribou and their plasticity to timing of spring events, while also quantifying phenotypic covariance between behavioural and life-history traits. Timing of migration for individual caribou was positively correlated with timing of snowmelt. The timing of parturition for individual caribou varied as a function of inter-annual variation in timing of snowmelt and green-up. Repeatability for migration timing was moderate, but low for timing of parturition. Plasticity did not affect reproductive success. We also did not detect any evidence of phenotypic covariance among any traits examined-timing of migration was not correlated with timing of parturition, and neither was there a correlation in the plasticity of these traits. Repeatability in migration timing suggests the possibility that the timing of migration in migratory herbivores could evolve if the repeatability detected in this study has a genetic or otherwise heritable basis, but observed plasticity may obviate the need for an evolutionary response. Our results also suggest that observed shifts in caribou parturition timing are due to plasticity as opposed to an evolutionary response to changing conditions. While this provides some evidence that populations may be buffered from the consequences of climate change via plasticity, a lack of repeatability in parturition timing could impede adaptation as warming increases.

Variation in the parasite communities of three co-occurring herbivorous coral reef fishes.

Parasites are important, diverse, and abundant components of natural ecosystems and can influence the behaviour and health of their hosts, inter- and intraspecific interactions, and ultimately community structure. Coral reefs are one of the world's most biodiverse ecosystems, yet our understanding of the abundance, diversity, and composition of parasite communities of coral reef fishes is limited. Here, the authors aimed to compare the abundance, richness and composition of parasite communities among three co-occurring herbivorous coral reef fishes (the barred rabbitfish Siganus doliatus, Ward's damsel Pomacentrus wardi and the obscure damsel Pomacentrus adelus) from an inshore reef of the Great Barrier Reef (GBR). In total, 3978 parasites (3869 endoparasites and 109 ectoparasites) from 17 families were recovered from 30 individuals of each of the three fish species (mean=44 ± 22 s.e. parasites per fish; range=0-1947 parasites per fish). The parasite communities of P. wardi and P. adelus were characterised by pennellid copepods, derogenid and lecithasterid digeneans and were distinct from those of S. doliatus that were characterised by a higher abundance of atractotrematid and gyliauchenid digeneans. The abundance and family richness of all parasites were greatest in S. doliatus (abundance: 22.1 ± 5.0 parasites per fish; richness: 3.2 ± 0.3 families per fish), intermediate in P. wardi (abundance: 4.8 ± 1.1 parasites per fish; richness: 2.3 ± 0.3 families per fish) and lowest in P. adelus (abundance: 1.4 ± 0.4 parasites per fish; richness: 0.9 ± 0.2 families per fish). Similarly, the abundance of endoparasites was greatest in S. doliatus (19.7 ± 5.1 endoparasites per fish), intermediate in P. wardi (2.6 ± 0.7 endoparasites per fish) and lowest in P. adelus (1.2 ± 0.4 endoparasites per fish). Ectoparasite abundances were also lowest for P. adelus (0.2 ± 0.1 ectoparasites per fish), and S. doliatus and P. wardi had comparable abundances of ectoparasites (1.3 ± 0.3 and 2.1 ± 0.5 parasites per fish, respectively). Similarities between the parasite assemblages of the two pomacentrids may be related to their similar behaviours and/or diets vs. those of the larger-bodied and more mobile rabbitfish. Investigating the causes and consequences of variation in parasite communities across a broader range of fish species will be critical to understand the potential role of parasites in coral reef ecosystems.

Indentation Plastometry of Particulate Metal Matrix Composites, Highlighting Effects of Microstructural Scale

Herein, it is concerned with the use of profilometry‐based indentation plastometry (PIP) to obtain mechanical property information for particulate metal matrix composites (MMCs). This type of test, together with conventional uniaxial testing, has been applied to four different MMCs (produced with various particulate contents and processing conditions). It is shown that reliable stress–strain curves can be obtained using PIP, although the possibility of premature (prenecking) fracture should be noted. Close attention is paid to scale effects. As a consequence of variations in local spatial distributions of particulate, the “representative volume” of these materials can be relatively large. This can lead to a certain amount of scatter in PIP profiles and it is advisable to carry out a number of repeat PIP tests in order to obtain macroscopic properties. Nevertheless, it is shown that PIP testing can reliably detect the relatively minor (macroscopic) anisotropy exhibited by forged materials of this type.