Initial Stage Of Penetration Research Articles

Effective and cleaner Zr (IV) tanning process based on the inert-surface modification of skin collagen by PEGylated epoxy copolymers

Zirconium tanning agent, which is mainly composed of low-toxic tetravalent zirconium (Zr4+) salts, has been considered the most promising eco-friendly tanning agent for leather manufacturing, due to its comparable tanning performance with trivalent chrome. However, in the initial penetration stage of the zirconium tanning process, macromolecular multinuclear complexes are commonly formed because of the rapid coordination between hydrated Zr4+, which can easily cross-link with active groups of neighboring collagen fibers and thus block subsequently even penetration of zirconium tanning agents, resulting in surface over-tanning and ununiform tanning effects. Herein, to address the aforementioned issues of conventional zirconium tanning, inert-surface modification of collagen fibers was proposed by using PEGylated epoxy copolymers (PEGMA-co-GMA, defined as PPG) to pretreat bated hide, based on the covalent reactions and hydrogen-bond interactions of PPG with amino and carboxyl groups on collagen fibers, respectively. After modification, the surface reactivity of skin collagen was significantly reduced, which was able to delay the cross-linking interactions with zirconium tanning agents and thus promote uniform penetration. Simultaneously, the extra hydroxyls produced from the ring-open reactions of epoxy groups could also mitigate the excessive coordinated complexation of hydrated Zr4+, leading to efficient penetration of zirconium tanning agents. Compared with conventional zirconium tanning, research results showed that this inert-surface modification strategy could comprehensively improve the overall leather performance with both efficient and uniform tanning effects. Moreover, the resultant leather qualities, including thermal stability, physical and mechanical properties, and organoleptic properties, are very comparable with chrome-tanned leather. In addition, attributing to the reaction between collagen amino and PPG, the use of sodium chloride was avoided, resulting in a cleaner salt-free pickling process. Altogether, this inert-surface modification strategy represents a significant step forward for effective and cleaner tanning technology, which will accelerate the wide application of Zr(IV) in place of traditional chrome tanning agents.

Investigation of the mechanical and ballistic properties of hybrid carbon/ aramid woven laminates

High-performance ballistic fibers, such as aramid fiber and ultra-high-molecular-weight polyethylene (UHMWPE), are commonly used in anti-ballistic structures due to their low density, high tensile strength and high specific modulus. However, their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure. In contrast, carbon fiber reinforced epoxy resin matrix composites (CFRP) have the characteristics of high modulus in the thickness direction and high shear resistance. However, carbon fibers are rarely used and applied for protection purposes. A hybridization with aramid fiber reinforced epoxy resin matrix composites (AFRP) and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites. The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated. Through conducting mechanical property tests and ballistic tests, two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software, respectively. The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced. The ballistic tests’ results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7% of AFRP. When CFRP was on the striking face, the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage. The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process. These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt% and 30 wt%.

The embedment of a high velocity rigid ogive nose projectile into a concrete target

The early stage of penetration of a rigid projectile into a target is denoted as the entrance stage. It begins when the nose tip impacts the target surface and the projectile starts its penetration into the target. The entrance stage is characterized by an increasing contact area between the projectile and the target which yields an increasing resistance and deceleration. This is the more difficult and less studied part of the penetration process. The present paper is focused on the entrance stage aiming at clarifying the interaction behavior during this early stage penetration and contributing to this less investigated problem.The literature survey indicates that the depth of the entrance stage is rather unclear and different researchers define the entrance stage depth differently. All definitions relate this depth to the projectile diameter. The shape of the deceleration curve is examined, and the linear deceleration-depth relationship assumed by the widely used spherical cavity expansion (SCE) approximation is criticized. This paper examines these definitions and postulates a new rational definition which agrees well with test data. A new analytical solution that is based on the SCE approximation is developed for the initial stage of penetration of a rigid projectile into a concrete medium. This modified spherical cavity expansion solution (denoted as SCEM) considers the variation of the “projectile-target” contact area with time, which is typical to the projectile entrance stage. Comparing the deceleration time histories of the new solution with the experimental data and with the DISCS model analysis results shows very good agreement, and the difference between the proposed analytical model and the commonly assumed deceleration-depth linear relationship is demonstrated. Characteristics of the entrance stage are analyzed and features like the embedment duration and the effect on the final penetration depth are examined.

ЯВНАЯ ФОРМУЛА ДЛЯ ГЛУБИНЫ ПРОНИКАНИЯ УДАРНИКА С КОНИЧЕСКОЙ ГОЛОВНОЙ ЧАСТЬЮ В АНИЗОТРОПНУЮ ПРЕГРАДУ

The field of application of Functionally Graded Materialsis steadily expanding, which stimulates research in the relevant areas. In relation to penetration mechanics, these are primarily experimental studies of multilayer barriers consisting of plates “in contact” with various mechanical properties. Despite intensive research, explicit formulas for integral penetration characteristics (penetration depth and ballistic limit) cannot be obtained, except for the case when sequential penetration of layers (barriers with large gaps between layers). In this article, explicit formulas for the depth of penetration into an semi-infinite shield and for the ballistic limit velocity applying penetration into a shield of a finite thickness are derived assuming that the hardness of the barrier material varies continuously depending on barrier depth. The theoretical analysis is based on a model that represents the normal stress at points on the surface of the penetrating body that are in contact with the barrier as a quadratic function of the normal component of local impactor velocity with a zero linear term (the Vitman - Stepanov model). Difference of the dynamic hardness in different points of impactor-barrier contact is taken into account. It is also assumed that the nose of the striker has the form of a straight circular cone and the initial stage of penetration when the striker is not completely immersed in the barrier is ignored.

Dual drug-loaded cubic liquid crystal gels for transdermal delivery: inner structure and percutaneous mechanism evaluations

The goal of this paper was to develop and evaluate dual component-loaded with the hydrophilic sinomenine hydrochloride (SH) and lipophilic cinnamaldehyde (CA) cubic liquid crystal gels for transdermal delivery. The gels was prepared with a vortex method using phytantriol/water (70:30, w/w) and characterized by polarized light microscopy, small-angle X-ray scattering and rheology. The inner structure of the gels were Pn3m cubic phase and exhibited a pseudoplastic fluid behavior. Furthermore, the in vitro release profile showed that the release behavior of the two drugs from cubic liquid crystal gels conformed to Higuchi equation and were dominated by Fick’s diffusion (n < 0.45). The ex vivo penetration experiment indicated that dual components-loaded liquid crystal gels can enhance and extend the skin permeation of these two drugs, especially the ratio of SH to CA is 1: 0.5. Finally, transdermal mechanisms were evaluated using laser scanning confocal microscopy and attenuated total reflectance-fourier transform infrared, hinting that hydrophilic and lipophilic drugs weaken each other’s transdermal velocity at the initial stage of penetration. In short, the dual drug-loaded liquid crystal gels was a promising strategy for transdermal applications in treatment of chronic disease.

Non-isothermal mechanodiffusion model of the initial stage of penetration of particle flow in a target surface

Non-isothermal mechanodiffusion model of the initial stage of penetration of particle flow in a target surface

Cuticle-degrading proteases of entomopathogenic fungi: from biochemistry to biological performance

Entomopathogenic fungi are among the most successful biocontrol agents for preventing economic loss from insects. The identification of virulent species or isolates, the development of formulation technology and the improvement of efficiency are avenues being pursuing by researchers in diverse scientific disciplines. A successful entomopathogenic fungus deploys a combination of mechanical and biochemical processes to overcome the first defensive barrier in insects, the integument. A precise understanding of the mechanisms underlying fungal pathogenicity, particularly the roles of enzymes such as proteases, is essential in order to highlight the potential of entomopathogenic fungi and increase their virulence via genetic modifications. Cuticle-degrading proteases are divided into subtilisin-like (Pr1) and trypsin-like (Pr2) proteases, which are secreted in the initial stages of penetration. The biochemical structure contains the catalytic triad Asp39, His69 and Ser224 in addition to Ca2+ binding sites. Studies have shown a molecular weight of almost 19–47 kDa, an optimal pH of 7–12 and an optimal temperature of 35–45 °C. Different species or isolates of entomopathogenic fungi exhibit differences in the secretion and activity of cuticle-degrading proteases, which may indicate their virulence capacity. Genetic engineering techniques have been developed to create isolates with protease overexpression. Such isolates have significantly higher virulence against the host because they not only ensure fungal penetration but also exhibit direct toxicity to insects.

Testing the limits of model membrane simulations-bilayer composition and pressure scaling.

Studying transfer of bioactive compounds across cell membranes by simulations attracts growing attention. To perform such calculations accurately, it is necessary to verify the validity of computational protocols established for description of unperturbed lipid bilayers also with translocating substances present. The current work reports the results from 1 μs long atomistic molecular dynamics simulations of two types of model plasma membranes-one built of a single phospholipid (DPPC) and one constructed of four types of phospholipids-in the presence of a drug-peptide complex experimentally known to cross cell membranes. The influence of membrane composition and of applied pressure scaling algorithm on the simulations outcome is analyzed with particular focus on membrane structure and on complex-lipid interactions during the initial penetration stage. It is found that the mixed composition of the membrane is important for correct assessment of the interactions with the complex both from purely structural perspective and because of the uneven charge distribution. The structure of the mixed lipid bilayer is affected more markedly by the pressure scaling algorithm. When the pressure is isotropically scaled, lipids are distributed almost homogeneously along the membrane in liquid ordered state. On semi-isotropic scaling, the lipid tails undergo significant rearrangement and a long-range ordered state is established. This results in "freezing" of the membrane and expulsion of the complex. The statistical analysis of the MD data points to the conclusion that a mixed-lipid membrane model with isotropic pressure scaling would be more suitable for describing the process of complex translocation across neoplastic membranes. © 2017 Wiley Periodicals, Inc.

Study on Protection Mechanism of 30CrMnMo-UHMWPE Composite Armor.

The penetration of a 30CrMnMo ultra-high molecular weight polyethylene armor by a high-speed fragment was investigated via experiments and simulations. Analysis of the projectile revealed that the nose (of the projectile) is in the non-equilibrium state at the initial stage of penetration, and the low-speed regions undergo plastic deformation. Subsequently, the nose-tail velocities of the projectile were virtually identical and fluctuated together. In addition, the effective combination of the steel plate and polyethylene (PE) laminate resulted in energy absorption by the PE just before the projectile nose impacts the laminate. This early absorption plays a positive role in the ballistic performance of the composite armor. Further analysis of the internal energy and mass loss revealed that the PE laminate absorbs energy via the continuous and stable failure of PE fibers during the initial stages of penetration, and absorbs energy via deformation until complete penetration occurs. The energy absorbed by the laminate accounts for 68% of the total energy absorption, indicating that the laminate plays a major role in energy absorption during the penetration process.

Temporal investigations of transient fuel spray characteristics from a multi-hole injector using dimensionless analysis

The breakup of high speed liquid jets and the spray formation from a multi-hole direct-injection injector were investigated by analyzing the temporal development of spray penetration and cone angle. Planar Mie scattering was applied to generate spray images under a wide range of operating conditions with ethanol, methanol and gasoline as test fuels. Dimensionless parameters such as Reynolds number (Re), Weber number (We), and gas-to-liquid density ratio (ρa/ρl) were used to enumerate the competition and balance of forces that dominated the spray formation, including the inertia force, viscous force, surface tension force and aerodynamic force. The results show that two temporally sequential stages exist during the spray formation, namely the initial stage and developed stage. During the initial stage, the spray penetration increases linearly with time after the start of injection (ASOI). The penetrating speed during the initial stage is primarily controlled by the competition between the inertia and surface tension while the aerodynamic force shows only minor influence. The duration of the initial stage of penetration is dependent on the competing process between inertia and viscous force as well as that between inertia and aerodynamic force. During the developed stage, the effect of aerodynamic forces becomes more influential on the spray penetration. The viscous force shows weak impact on developed stage penetration under low Reynolds number (Re<12,500) conditions. In contrast with the strongly time-dependent penetration, the plume angle of the emerging jets stays relatively constant during the entire injection duration. Based on the above analysis, new dimensionless correlations have been established to quantitatively characterize the effects of competing forces on spray penetration and cone angle. Compared to the classical correlations, these new correlations explicitly express the relative importance of each force during different temporal stages of spray formation. Therefore, they provide more insight into the physical mechanism of high pressure spray formation process.

Initial stage of imbibition of a porous material with allowance for convective mass transfer

Consideration has been given to a model of heat- and mass-exchange processes in a porous body with two types of pores that is suitable for description of the initial stage of penetration of a substance into a porous system (or of the inverse process: withdrawal of a substance from it). Convective transfer of the substance is allowed for in large channels (pores). The solution of the problem with supplementary conditions, which are typical in practice and with which the kinetic function of imbibition (withdrawal) of the porous medium and the density of the substance flux from the body were found, has been obtained. Certain limiting cases have been investigated.

Impurity effects on the intergranular liquid bismuth penetration in polycrystalline nickel

The effects of impurities on the intergranular penetration of Bi based liquids in polycrystalline Ni at 700 °C were systematically investigated. In comparison with a nominally pure Ni (99.9945%), the presence of a total amount of <0.5 at.% impurities of Mn, Fe and Si in the Ni increased the penetration length by six times when a near-equilibrium Bi–Ni liquid was applied; when an initially pure Bi liquid was applied, this increment further enlarged to ∼20 times in the initial penetration stage. In a second set of controlled experiments, the addition of Mn, Sn and Fe to the liquid Bi–Ni all enhanced the intergranular penetration, but produced different kinetics and morphologies. We extended a concept that was initially proposed in the Rice–Wang model for grain boundary embrittlement to explain our observations of the impurity-enhanced intergranular penetration based on a theory that segregation of an impurity could reduce the grain boundary energy more rapidly than the solid–liquid interfacial energy. Correspondingly, a new analytical model for the effect of adding a third impurity on changing the equilibrium dihedral angle and the associated intergranular penetration kinetics has been derived for the dilute solution limit. Furthermore, we demonstrated that the interplay of bulk phase equilibria, interfacial segregation, transport (dissolution, precipitation and diffusion) processes and stress generation could effectively explain a variety of different intergranular penetration behaviors and morphologies that have been observed in the experiments conducted using 10 different combinations of the solid and liquid metals. The framework for understanding the impurity effects on intergranular liquid penetration developed in this study can be applied to other materials systems. This study has practically importance for understanding and controlling liquid metal corrosion and embrittlement.

Absorption/expulsion of oligomers and linear macromolecules in a polymer brush

The absorption of free linear chains in a polymer brush was studied with respect to chain size L and compatibility ψ with the brush by means of Monte Carlo (MC) simulations and density functional theory (DFT)/self-consistent field theory (SCFT) at both moderate, σg=0.25, and high, σg=1.00, grafting densities using a bead-spring model. Different concentrations of the free chains 0.0625≤ϕo≤0.375 are examined. Contrary to the case of ψ=0 when all species are almost completely ejected by the polymer brush irrespective of their length L, for ψ&amp;lt;0 we find that the degree of absorption (absorbed amount) Γ(L) undergoes a sharp crossover from weak to strong (≈100%) absorption, discriminating between oligomers, 1≤L≤8, and longer chains. For a moderately dense brush, σg=0.25, the longer species, L&amp;gt;8, populate predominantly the deep inner part of the brush, whereas in a dense brush σg=1.00 they penetrate into the “fluffy” tail of the dense brush only. Gyration radius Rg and end-to-end distance Re of absorbed chains thereby scale with length L as free polymers in the bulk. Using both MC and DFT/SCFT methods for brushes of different chain length 32≤N≤256, we demonstrate the existence of unique critical value of compatibility ψ=ψc&amp;lt;0. For ψc(ϕo) the energy of free chains attains the same value, irrespective of length L whereas the entropy of free chain displays a pronounced minimum. At ψc all density profiles of absorbing chains with different L intersect at the same distance from the grafting plane. The penetration/expulsion kinetics of free chains into the polymer brush after an instantaneous change in their compatibility ψ displays a rather rich behavior. We find three distinct regimes of penetration kinetics of free chains regarding the length L: I (1≤L≤8), II (8≤L≤N), and III (L&amp;gt;N), in which the time of absorption τ grows with L at a different rate. During the initial stages of penetration into the brush one observes a power-law increase of Γ∝tα with power α∝−ln ϕo, whereby penetration of the free chains into the brush gets slower as their concentration rises.

A Key Enzyme of the Leloir Pathway Is Involved in Pathogenicity of Leptosphaeria maculans Toward Oilseed Rape

Agrobacterium tumefaciens-mediated random insertional mutagenesis was used to investigate pathogenicity determinants in Leptosphaeria maculans. One tagged nonpathogenic mutant, termed m186, is analyzed in detail here. Microscopic analyses of infected plant tissues revealed that m186 is specifically blocked at the invasive growth phase after an unaffected initial penetration stage and is unable to switch to the necrotrophic lifestyle. In addition, m186 exhibits an altered cell wall and seems to be affected in its ability to produce cell-wall-degrading enzymes. The T-DNA insertion occurs in the intergenic region between two head-to-tail genes, leading to a constitutive upregulation of their expression. Complementation experiments showed that only one of these two genes, Lmepi, fully accounts for the mutant phenotype. Bioinformatics and expression analyses along with functional studies suggested that the Lmepi gene encodes for the highly conserved UDP-glucose-4-epimerase, a key enzyme of the Leloir pathway involved in galactose metabolism. For the third time, this study highlights the intimate connection between primary metabolism and pathogenicity in L. maculans. This finding, along with similar data obtained from the related species Stagonospora nodorum, indicates the importance of in planta nutrition for the success of infection of plants by fungi belonging to class Dothideomycete.

TheLmgpi15gene, encoding a component of the glycosylphosphatidylinositol anchor biosynthesis pathway, is required for morphogenesis and pathogenicity inLeptosphaeria maculans

Random insertional mutagenesis was used to investigate pathogenicity determinants in Leptosphaeria maculans. One tagged nonpathogenic mutant, termed m20, was analysed in detail here. The mutant phenotype was investigated by microscopic analyses of infected plant tissues and in vitro growth assays. Complementation and silencing experiments were used to identify the altered gene. Its function was determined by bioinformatics analyses, cell biology experiments and functional studies. The mutant was blocked at the invasive growth phase after an unaffected initial penetration stage, and displayed a reduced growth rate and an aberrant hyphal morphology in vitro. The T-DNA insertion occurred in the intergenic region between two head-to-tail genes, leading to a complex deregulation of their expression. The unique gene accounting for the mutant phenotype was suggested to be the orthologue of the poorly conserved Saccharomyces cerevisiae gpi15, which encodes for one component of the glycosylphosphatidylinositol (GPI) anchor biosynthesis pathway. Consistent with this predicted function, a functional translational fusion with the green fluorescent protein (GFP) was targeted to the endoplasmic reticulum. Moreover, the mutant exhibited an altered cell wall and addition of glucosamine relieved growth defects. It is concluded that the GPI anchor biosynthetic pathway is required for morphogenesis, cell wall integrity and pathogenicity in Leptosphaeria maculans.

Penetration of a glass-faced transparent elastomeric resin by a lead–antimony-cored bullet

The penetration of the lead antimony-cored 7.62 mm × 51 mm bullet into a glass-faced polyurethane elastomeric polymer resin has been studied. The resulting craters in the resin contained elongated bullet core material that had a significant amount of porosity. A simple linear viscoelastic model was applied to AUTODYN-2D to describe the behaviour of the resin and numerical results of the penetration mechanism and depth-of-penetration appeared to match experimental observations well. Analysis of the high speed photography and a numerical model of this bullet penetrating a viscoelastic polymer showed that during the initial stages of penetration, the projectile is essentially turned inside out. Furthermore, the shape of the cavity was defined by the elastic relaxation of the polymer that led to compression of the core material. A weight analysis of the penetrated materials showed that using a thicker tile of glass resulted in better ballistic performance.

Numerical Simulation of the Spontaneous Penetration of Liquids into Cylindrical Capillaries

Dynamics of spontaneous capillary penetration of a liquid into a cylindrical pore is studied numerically over the entire duration of an experiment, including the initial stages of penetration during which inertial effects are dominant. Partial slip in the vicinity of the moving contact-line is allowed by using an empirical constitutive relation between the dynamic contact angle and contact line speed in order to avoid the stress singularity arising from the presence of the moving contact line on the solid wall. A finite-difference scheme on a staggered body-fitted grid is used to solve for the time-dependent flow field and to determine the time evolution of the shape of the advancing meniscus. The results of dynamic simulations of capillary rise under both normal and microgravity conditions are compared with the reported experimental observations. The simulation results are found to be in good agreement with the experimental measurements in both cases. Numerical simulations capture the different flow regimes identified in previous studies of spontaneous capillary penetration. The velocity dependence of the dynamic contact line is found to have a significant effect on kinetics of wetting in the intermediate-time flow regime, wherein the capillary force is balanced by convective losses.

A case study from the interaction of strawberry and Botrytis cinerea highlights the benefits of comonitoring both partners at genomic and mRNA level

Strawberry Fragaria x ananassa (cv. Korona) was inoculated with Botrytis cinerea by dipping berries in a conidial suspension. Colonization by the pathogen was monitored using real-time PCR, ELISA and ergosterol assays, the first showing the highest sensitivity. The expression of pathogen beta-tubulin and six polygalacturonases (Bcpg1-6) and three host defence genes (polygalacturonase-inhibiting protein (FaPGIP) and two class II chitinases) were monitored using real-time RT-PCR. The maximum transcript levels of the host defence genes occurred at 16 h postinoculation (hpi) at the presumed initial penetration stage. The unique transcript profile of Bcpg2 over the 96-h incubation time and its high transcript levels relative to those of the other Bcpgs at 8-24 hpi suggest that the gene has a specific role in the penetration stage. Bcpg1 was expressed constitutively at a relatively high level in actively growing mycelia throughout the experimental period. Comparison of the transcript profiles indicated that Bcpg1 and Bcpg3-6 were coordinately regulated.

Laser-induced activation of stearin transparency

The time delay in the initial stage of penetration of intense laser radiation into stearin that strongly scatters light has been experimentally detected. This phenomenon, which occurs during the melting of stearin, is explained by the lengthy breakdown process of its irregular spatial structure. It is assumed that the transition of stearin from a superheated, strongly scattering solid state to a liquid occurs via activation transitions over metastable states. A model description is given of the penetration kinetics of the radiation as a consequence of homogenization of the medium. © 2004 Optical Society of America

In-situ observation of slag penetration into MgO refractory

The behavior of slag penetration into MgO refractory was investigated by combining in-situ X-ray observation with microstructural analysis of the samples after penetration experiments. The following results are obtained. The slag penetrates rapidly into the refractory, reacting with MgO particles in the refractory. The slag penetrates unevenly into the refractory with uneven pore size in a route like a tree, firstly along the main route (the surface of large MgO particles), and then extending to the branch route, while evenly into the refractory with even pore size. The rate of slag penetration increases with increasing pore radius and apparent porosity of the refractory, T · Fe concentration in the slag and temperature, and with decreasing the slag basicity (C/S ratio). In the case of the Al2O3-bearing slag, the rate of slag penetration is less than that of Al2O3-free slag in the initial stage. The penetration also stops much earlier than that of the Al2O3-free slag, and then the penetration height remains almost constant. In the initial stage of penetration, the penetration height is proportional to the square root of penetration time. Slag penetration is deduced as stopping due to the following: (1) the melting point and viscosity of the penetrated slag increase, and the surface tension of the penetrated slag decreases with decreasing the FetO concentration in the penetrated slag consumed by the reaction between FetO and MgO particles; (2) in the 10mass% Al2O3-bearing slag, the pore size in the refractory is reduced by the spinel formed on the pore surface by the reaction between Al2O3 in the penetrated slag and MgO particles in the refractory.