Plastic Character Research Articles

Effects of hydrogen on the nanomechanical properties of a bulk metallic glass during nanoindentation

In this reported work, the effects of hydrogen on the nanomechanical properties of a Zr55Cu30Ni5Al10 bulk metallic glass were investigated. The experimental results demonstrated that the nanohardness of the subject material was significantly reduced as the hydrogen content in glass increased, which was caused by the induced softening from the presence of hydrogen as observed by a decrease in the elastic modulus of the glass. The flow serration of the load-displacement on the glass during nanoindentation gradually became smooth when the hydrogen content was high, which was similar to the nanoindentation loading rate effect. The transition in the flow serration was a distinct physical phenomenon, suggesting a change of in the character of plasticity. A single shear band couldn't accommodate the imposed strain rapidly enough, and consequently multiple shear bands must operate simultaneously. The electronic structure of the hydrogenated Zr55Cu30Ni5Al10 were measured by X-Ray photoemission spectroscopy (XPS). In comparison with their quaternary counterparts, the XPS spectra of the hydrogenated samples were characterized by a shift of the Zr and Al band to lower binding energies. These suggested that the presence of solute hydrogen atoms resulted in the occurrence of the valence electron transferring from the Zr 3d band to the ZrH bonding state, which would weaken the surrounding metallic glass.

Learning and retrieval behavior in recurrent neural networks with pre-synaptic dependent homeostatic plasticity

The plastic character of brain synapses is considered to be one of the foundations for the formation of memories. There are numerous kinds of such phenomenon currently described in the literature, but their role in the development of information pathways in neural networks with recurrent architectures is still not completely clear. In this paper we study the role of an activity-based process, called pre-synaptic dependent homeostatic scaling, in the organization of networks that yield precise-timed spiking patterns. It encodes spatio-temporal information in the synaptic weights as it associates a learned input with a specific response. We introduce a correlation measure to evaluate the precision of the spiking patterns and explore the effects of different inhibitory interactions and learning parameters. We find that large learning periods are important in order to improve the network learning capacity and discuss this ability in the presence of distinct inhibitory currents.

Synthesis and properties of a novel bio-based polymer from modified soybean oil

Maleated acrylated epoxidized soybean oil (MAESO) was prepared by acrylated epoxidized soybean oil (AESO) and maleic anhydride. AESO were obtained by the reaction of epoxidized soybean oil (ESO) with acrylic acid as the ring-opening reagent. The polymer was prepared by MAESO react with styrene. The structures of the products were studied by Fourier transformation infrared spectrometer (FT-IR), and were consistent with the theoretical structures. Swelling experiment indicated that the crosslinking degree increased with increasing epoxy value of ESO. Thermal properties was tested by thermo-gravimetric analysis (TG) and differential scanning calorimetry analysis (DSC), indicating that glass transition temperature (Tg) of the polymer increased with increasing epoxy value of ESO, and thermal stability of polymer have a good correlation with the crosslinking degree. Mechanical properties analysis presented that tensile strength and impact strength affected by epoxy value of ESO. With the increase of epoxy value, the tensile strength increase, while the impact strength decrease. The property of the polymer ranged from elastomer to plastic character depended on the functionality of the ESO.

Synthesis and characterization of a novel bio-based resin from maleated soybean oil polyols

In this paper, a novel bio-based resin was prepared by the radical copolymerization of maleated soybean oil polyols (MSBOP) and styrene (ST). Structure of the product was studied by Fourier transformation infrared spectrometer (FT-IR), and the result was found to be consistent with that of theoretical structure. Swelling experiments indicated that the crosslinking degree increased with the increase of hydroxyl value. Thermal analysis by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TG) revealed that glass transition temperature (Tg) of the polymer increased with increasing hydroxyl values, and that its thermal stability showed a good correlation with the hydroxyl value. The tensile strength and impact strength were significantly affected by the hydroxyl value of soybean oil polyols. With increasing hydroxyl value, the tensile strength presented an increasing trend, while the impact strength showed a decreasing one. Moreover, the property of the polymer from elastomer to plastic character also depended on the functionality of the hydroxyl value of soybean oil polyols.

On the reality of local and ecological races in lymnaeid snails (Mollusca, Gastropoda, Lymnaeidae)

The reality of ecological and local races was investigated in two widespread Palearctic species of lymnaeid snails (Lymnaea stagnalis and Radix auricularia). Several methods of statistical analysis were used, including two-way ANOVA, cluster analysis, and discriminant analysis for six plastic shell characters. It was shown that none of the methods used could convincingly demonstrate that ecological and local races were present in the studied species. Even in cases when statistically significant differences among the populations in the morphology of shells were revealed, these differences were very small and did not correspond to the meaning that was put into the concept of “race” by malacologists in the past. Perhaps, the formation of such races in pond snails is possible only in case of populations being formed in suboptimal conditions, for example, in thermal springs or at large depths. This being the case, the distinguishing of races requires using other shell characters, both quantitative and qualitative ones.

Polymorphism of spawners of the resident form of European river lamprey Lampetra fluviatilis (Petromyzontidae)

Data on polymorphism (plastic and meristic characters) are obtained for spawners of resident nonparasitic form of European river lamprey Lampetra fluviatilis from the Serebristaya River. The new data verify the diagnosis of this species and contribute to the formulation of a hypothesis on the presence of several phenotypic groups: dwarf, small-sized, and common. Analysis of plastic characters and of the number of trunk myomeres demonstrated that the values of these characters reliably depend on position of lampreys in a certain discerned group. Some aspects of biology of this species are discussed: spawning and interaction between resident nonparasitic river and migrating parasitic lampreys.

Sex Differences and Sex Identification in the Small-Scaled Scorpionfish, Scorpaena Porcus (Scorpaenidae, Scorpaeniformes)

Abstract Sex differences and the ability to determine the sex of Scorpaena porcus (Linnaeus, 1758) on morphological characters were studied in the population inhabiting coastal waters of the Black Sea near the southern coast of Crimea. These differences were revealed in size (females are larger than males) and in proportions of the body. It is found that variation of the absolute and relative values in plastic characters is higher in females compared with males. It is shown that in 92 % of individuals belonging to S. porcus we can determine the sex using morphological characters with a probability of 99.9-100 %.

Morphological and ecological differentiation of sympatric whitefish species of the genus Coregonus from Lake Taymyr

Results of the morphological analysis of ecology and feeding of two sympatric forms of whitefishes (lacustrine and lacustrine–riverine) inhabiting Lake Taymyr (the Taymyr Peninsula) are presented in the article. It is revealed that these forms do not differ in the number of gill rakers on the first branchial arch and in the number of perforated scales in the lateral line, but they do differ in plastic characters, spawning periods, and area. At the age of 2–3 years they become separate in regards to feeding type. It is assumed that both forms of whitefishes inhabited Lake Taymyr simultaneously with the filling of the lake basin. Apparently the taxonomic status of the sympatric whitefishes from Lake Taymyr is broader than the term “ecological form.”

Physico‐Chemical and Rheological Properties of Gellan in Aqueous‐Salt Solutions and Oilfield Saline Water

SummaryThe physico‐chemical and rheological properties of low acyl gellan (LAG) were investigated in aqueous solutions of various salts. 1H NMR spectroscopic study of LAG was conducted in salt‐free solutions at different temperatures. FTIR spectra revealed that the characteristic bands of both asymmetric and symmetric carboxylate groups are shifted to higher frequency regions as a result of effective surrounding of glucuronate residuesby mono‐ and divalent cations of salts. According to viscometricresults the effectiveness of salts to enhance gelation of gellan changes in the following order: BaCl2 > CaCl2 ≈ MgCl2 > KCl > NaCl. The behavior of LAG in model aqueous‐salt solutions and real oilfield saline water was evaluated by means of rheological measurements.The shear rate (and effective viscosity) of 0.5 wt.% gellan solution versus shear stress increases (and decreases) in the sequence of CaCl2 > MgCl2 > KCl > NaCl demonstrating the pseudo plastic character. The sol‐gel and liquid‐solid phase transitions of gellan solutionswere observed upon addition of oilfield water containing 73 g · L−1 of alkaline and alkaline earth metal ions. The effectiveness of salts to induce the separation of liquid and solid phases changes in the sequence: NaCl > KCl > MgCl2 ≈ CaCl2 ≈ BaCl2. The mechanical properties of gellan gels under compression were studied and the Young modules and breaking stresses were found. Sol‐gel transition of gellan solution inside of sand pack model was demonstrated. The hydrodynamic behavior of 0.5 wt.% gellan solution injected into the sand pack model with high (20 d) and low (2 d) permeability is useful to model the oil reservoirs in the process of enhanced oil recovery. The influence of clay minerals – bentonite on the rheological characteristics of gellan solution was evaluated for simulation of drilling mud ability to carry up the drilled rock particles from the bottomhole of the well to the surface.

Phase-field slip-line theory of plasticity

A variational approach to determine the deformation of an ideally plastic substance is proposed by solving a sequence of energy minimization problems under proper conditions to account for the irreversible character of plasticity. The flow is driven by the local transformation of elastic strain energy into plastic work on slip surfaces, once that a certain energetic barrier for slip activation has been overcome. The distinction of the elastic strain energy into spherical and deviatoric parts is used to incorporate in the model the idea of von Mises plasticity and isochoric plastic strain. This is a “phase field model” because the matching condition at the slip interfaces is substituted by the evolution of an auxiliary phase field that, similar to a damage field, is unitary on the elastic phase and null on the yielded phase. The slip lines diffuse in bands, whose width depends upon a material length-scale parameter.Numerical experiments on representative problems in plane strain give solutions with noteworthy similarities with the results from classical slip-line field theory, but the proposed model is much richer because, accounting for elastic deformations, it can describe the formation of slip bands at the local level, which can nucleate, propagate, widen and diffuse by varying the boundary conditions. In particular, the solution for a long pipe under internal pressure is very different from the one obtainable from the classical macroscopic theory of plasticity. For this case, the location of the plastic bands may be an insight to explain the premature failures that are sometimes encountered during the manufacturing process. This practical example enhances the importance of this new theory based on the mathematical sciences.

APA-style human milk fat analogue from silkworm pupae oil: Enzymatic production and improving storage stability using alkyl caffeates.

Silkworm pupae oil derived from reeling waste is a rich source of α-linolenic acid (ALA), which has multipal applications. ALAs were added in sn-1, 3 positions in a triacylglycerol (TAG) to produce an APA-human milk fat analogues (APA-HMFAs, A: α-linolenic acid, P: palmitic acid). The optimum condition is that tripalmitin to free fatty acids of 1:12 (mole ratio) at 65 °C for 48 h using lipase Lipozyme RM IM. Results show that, the major TAG species that comprised APA-HMFAs were rich in ALA and palmitic acid, which contained 64.52% total unsaturated fatty acids (UFAs) and 97.05% PA at the sn-2 position. The melting point of APA was −27.5 °C which is much lower than tripalmitin (40.5 °C) indicating more plastic character. In addition, the practical application of alkyl caffeates as liposoluble antioxidants in APA was developed. Alkyl caffeate showed a superior IC50 (1.25–1.66 μg/mL) compared to butyl hydroxy anisd (1.67 μg/mL) and L-ascorbic acid-6-palmitate (L-AP) (1.87 μg/mL) in DPPH analysis. The addition of ethyl caffeate to oil achieved a higher UFAs content (73.58%) at high temperatures. Overall, APA was obtained from silkworm pupae oil successfully, and the addition of caffeates extended storage ranges for APA-HMFAs.

The evolution of avian wing shape and previously unrecognized trends in covert feathering.

Avian wing shape has been related to flight performance, migration, foraging behaviour and display. Historically, linear measurements of the feathered aerofoil and skeletal proportions have been used to describe this shape. While the distribution of covert feathers, layered over the anterior wing, has long been assumed to contribute to aerofoil properties, to our knowledge no previous studies of trends in avian wing shape assessed their variation. Here, these trends are explored using a geometric-morphometric approach with landmarks describing the wing outline as well as the extent of dorsal and ventral covert feathers for 105 avian species. We find that most of the observed variation is explained by phylogeny and ecology but shows only a weak relationship with previously described flight style categories, wing loading and an investigated set of aerodynamic variables. Most of the recovered variation is in greater primary covert feather extent, followed by secondary feather length and the shape of the wing tip. Although often considered a plastic character strongly linked to flight style, the estimated ancestral wing morphology is found to be generally conservative among basal parts of most major avian lineages. The radiation of birds is characterized by successive diversification into largely distinct areas of morphospace. However, aquatic taxa show convergence in feathering despite differences in flight style, and songbirds move into a region of morphospace also occupied by basal taxa but at markedly different body sizes. These results have implications for the proposed inference of flight style in extinct taxa.

Evolution of environmental cues for phenotypic plasticity.

Phenotypically plastic characters may respond to multiple variables in their environment, but the evolutionary consequences of this phenomenon have rarely been addressed theoretically. We model the evolution of linear reaction norms in response to several correlated environmental variables, in a population undergoing stationary environmental fluctuations. At evolutionary equilibrium, the linear combination of environmental variables that acts as a developmental cue for the plastic trait is the multivariate best linear predictor of changes in the optimum. However, the reaction norm with respect to any single environmental variable may exhibit nonintuitive patterns. Apparently maladaptive, or hyperadaptive plasticity can evolve with respect to single environmental variables, and costs of plasticity may increase, rather than reduce, plasticity in response to some variables. We also find conditions for the evolution of an indirect environmental indicator that affects expression of a plastic phenotype, despite not influencing natural selection on it.

Sarcodon atroviridis sensu lato, a stipitate hydnoid from Amazonian campinarana, Roraima, Brazil

Sarcodon atroviridis sensu lato has a rich nomenclatural history as a result of its variable morphology. Here we discuss the species most plastic morphological characters as well as its ecology and distribution, and we report it for the first time from the State of Roraima, Brazil. Color images of the basidiomata, complete descriptions and microscopic images are also provided.

Effects of hexagonal boron nitride on dry compression mixture of Avicel DG and Starch 1500

The objective of this study was to investigate the lubrication properties of hexagonal boron nitride (HBN) on a (1:1) binary mixture of Avicel DG and Starch 1500 after using the dry granulation–slugging method and compare it with conventional lubricants, such as magnesium stearate (MGST), glyceryl behenate (COMP) and stearic acid (STAC). MGST is one of the most commonly used lubricants in the pharmaceutical industry. However, it has several adverse effects on tablet properties. In our current study, we employed various methods to eradicate the work hardening phenomenon in dry granulation, and used HBN as a new lubricant to overcome the adverse effects of other lubricants on tablet properties. HBN was found to be as effective as MGST and did not show any significant adverse effects on the crushing strength or work hardening. From the scanning electron microscope (SEM) images, it was concluded that HBN distributed better than MGST. As well as showing better distribution, HBN’s effect on disintegration was the least pronounced. Semi-quantitative weight percent distribution of B and N elements in the tablets was obtained using EDS (energy dispersive spectroscopy). Based on atomic force microscope (AFM) surface roughness images, formulations prepared with 1% HBN showed better plastic character than those prepared with MGST.

A critical review of the current taxonomy of the genus Daphnia O. F. Müller, 1785 (Anomopoda, Cladocera).

The genus Daphnia O. F. Müller, 1785 (Anomopoda, Cladocera) has become a model genus for ecological, toxicological, and evolutionary studies. At the same time, Daphnia is a well-known example of a genus with a confused taxonomy. This review aims to identify the main sources of confusion (natural and human-caused) for the current taxonomy of Daphnia. A complete check-list of all species-group names of Daphnia was built using the available literature sources. I graphed the total number of taxa and number of valid taxa described during each year, and estimated a curve of accumulation of formal taxa from year to year. Four main periods in the history of Daphnia taxonomy were recognized, with the latest decades showing an increased rate of valid taxa to more than 50%. Overall, only 24 % of 361 known taxa of species rank are valid. A failure to find real, sometimes fine-scale diagnostic characters, led to a tradition of pseudo-taxonomy based mainly on the body shape and other phenotypically plastic characters, e.g. associated with defensive structures. I recommend revising the suite of taxonomically informative characters by emphasizing the anatomical details of males and thoracic limbs of both males and females. Such a revision of global scale, should be conducted in close coordination with phylogenetic studies. But this revision is impossible without accurate redescriptions of all previously described taxa, and a continuous step-by-step resolving of taxonomic problems in each species group.

Electronic structure, elastic and thermal properties of semiconductor GaX (X = N, P, As, Sb) with zinc blende from first-principles calculation

The band structure, density of states, elastic properties and thermal properties of semiconductor GaX (X = N , P , As , Sb ) with zinc blende were calculated by using the first principle plane-wave pseudo-potential methods based on density functional theory (DFT). The band structure and density of states for GaN , GaP , GaAs and GaSb show that GaX compounds are semiconductors with a direct band gap of 1.542, 1.445, 0.34 and 0.257 eV, respectively. The elastic constants and modulus are calculated showing that GaX are mechanically stable and GaN has the largest modulus. The anisotropy factor, internal-strain parameter, shear to bulk modulus and Poisson's ratio are also calculated indicating that GaX exhibit a brittle, anisotropic and plastic character. The dependencies of the Debye temperature, heat capacity, enthalpy, the entropy and free energy on temperature are also investigated. Comparisons with the available experiment and other theoretical calculation show reasonable agreement.

Intrinsic conformational plasticity of native EmrE provides a pathway for multidrug resistance.

EmrE is a multidrug resistance efflux pump with specificity to a wide range of antibiotics and antiseptics. To obtain atomic-scale insight into the attributes of the native state that encodes the broad specificity, we used a hybrid of solution and solid-state NMR methods in lipid bilayers and bicelles. Our results indicate that the native EmrE dimer oscillates between inward and outward facing structural conformations at an exchange rate (kex) of ∼300 s–1 at 37 °C (millisecond motions), which is ∼50-fold faster relative to the tetraphenylphosphonium (TPP+) substrate-bound form of the protein. These observables provide quantitative evidence that the rate-limiting step in the TPP+ transport cycle is not the outward–inward conformational change in the absence of drug. In addition, using differential scanning calorimetry, we found that the width of the gel-to-liquid crystalline phase transition was 2 °C broader in the absence of the TPP+ substrate versus its presence, which suggested that changes in transporter dynamics can impact the phase properties of the membrane. Interestingly, experiments with cross-linked EmrE showed that the millisecond inward-open to outward-open dynamics was not the culprit of the broadening. Instead, the calorimetry and NMR data supported the conclusion that faster time scale structural dynamics (nanosecond–microsecond) were the source and therefore impart the conformationally plastic character of native EmrE capable of binding structurally diverse substrates. These findings provide a clear example how differences in membrane protein transporter structural dynamics between drug-free and bound states can have a direct impact on the physical properties of the lipid bilayer in an allosteric fashion.

A new perspective on market dynamics

Several researchers have pointed out that if marketing is to develop as a discipline and contribute to solving complex business and societal challenges, it should question the neoclassical view of markets and develop its own theory of markets. Efforts in this direction indicate an emerging view of markets as dynamic, subjective, and subject to multiple change efforts. However, the neoclassical view of objective, detached, and deterministic market still influences the dominant models used to describe market change. We argue that in order to better understand market dynamics, both academics and practitioners need new concepts and constructs that go beyond existing linear process and development stage models. We seek to contribute to improved understanding of markets by studying a special characteristic of markets that enables market dynamics. Borrowing a term used by Alderson (1957: 277), we propose that markets are characterized by plasticity, that is, a “potentiality for being remolded and responding in a different way thereafter.” Even though the plasticity concept was introduced into the marketing literature nearly 60 years ago, the plastic character of markets remains underresearched. This article investigates the meaning and manifestations of market plasticity, drawing analogies from the physical, natural, and social sciences. We define market plasticity as the market’s capacity to take and retain form and propose that the dialectic between market stability and market fluidity lies at the heart of market change.

Compression parameters of hexagonal boron nitride on direct compression mixture of microcrystalline cellulose and modified starch

The objective of this study was to investigate the effects of conventional lubricants including a new candidate lubricant “hexagonal boron nitride (HBN)” on direct compression powders. Lubricants such as magnesium stearate (MGST), glyceryl behenate, stearic acid, talc and polyethylene glycol6000 were studied and tablets were manufactured on a single station instrumented tablet press. This study comprised the continuation of our previous one, so mixture of microcrystalline cellulose and modified starch was used as a master formula to evaluate effects of lubricants on pharmaceutical excipients that undergo complete plastic deformation without any fragmentation under compression pressure. Bulk and tapped densities, and Carr’s index parameters were calculated for powders. Tensile strength, cohesion index, lower punch ejection force and lubricant effectiveness values were investigated for tablets. The deformation mechanisms of tablets were studied during compression from the Heckel plots with or without lubricant. MGST was found to be the most effective lubricant and HBN was found very close to it. HBN did not show a significant negative effect on the crushing strength and disintegration time of the tablets when we compared with MGST. Based on the Heckel plots at the level of 1%, formulation prepared with HBN showed the most pronounced plastic character.