Tip Damage Research Articles

A micromechanical approach for mixed mode I/II failure assessment of cracked highly orthotropic materials such as wood

Mixed mode I/II fracture criterion based on strain energy density theory is presented for failure investigation of cracked composite materials. Crack is assumed to occur along the fibers in a highly orthotropic body. A new definition for fracture toughness of crack tip damage zone is proposed and employed to include the effects of dissipated energy due to formation of considerable fracture process zone. As crack propagation occurs between fibers in the isotropic matrix, reinforcement isotropic solid model is employed as a superior material model. Elastic and fracture properties of damage zone are characterized as a function of undamaged matrix properties and micro-crack density. Center notched disk tension (CNDT) specimen is introduced and employed for fracture tests. Comparison of the fracture limit curves with experimental data proves the capability of the new proposed mixed mode fracture criterion for fracture investigation of orthotropic materials.

Mutation of MEDIATOR 18 and chromate trigger twinning of the primary root meristem in Arabidopsis.

Plants adapt to soil injury and biotic stress via cell regeneration. In Arabidopsis, root tip damage by genotoxic agents, antibiotics, UV light and cutting induces a program that recovers the missing tissues through activation of stem cells and involves ethylene response factor 115 (ERF115), which triggers cell replenishment. Here, we show that mutation of the gene encoding an MED18 subunit of the transcriptional MEDIATOR complex and chromate [Cr(VI)], an environmental pollutant, synergistically trigger a developmental program that enables the splitting of the meristem in vivo to produce twin roots. Expression of the quiescent centre gene marker WOX5, auxin-inducible DR5:GFP reporter and the ERF115 factor traced the changes in cell identity during the conversion of single primary root meristems into twin roots and were induced in an MED18 and chromate-dependent manner during the root twinning events, which also required auxin redistribution and signalling mediated by IAA14/SOLITARY ROOT (SLR1). Splitting of the root meristem allowed dichotomous root branching in Arabidopsis, a poorly understood process in which stem cells may act to enable whole organ regeneration.

Cricotopus lebetis Intraspecific Competition and Damage to Hydrilla

Cricotopus lebetis Sublette (Diptera: Chironomidae) is an aquatic insect adventive in Florida. Evidence from previous studies suggest the insect may have value as an augmentative biological control agent for hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), but there are gaps in knowledge of the biology and life history traits. To increase understanding of this insect, this study was comprised of 3 experiments. In the first experiment, we investigated the productivity and survival rate of C. lebetis across 6 generations by analyzing our colony data. Then the effect of intraspecific competition on the rates of pupal and adult eclosion was studied by monitoring hydrilla tips in test tubes with varying numbers of larvae. Finally, the level of hydrilla stem tip damage caused by a C. lebetis larva was determined by monitoring tip damage following feeding of a known number of larvae on a standardized number of hydrilla tips. The first experiment revealed the average survival rate of C. lebetis from egg to adult was 16.4%. Approximately a third of the females (30.2%) oviposited. The egg masses had an average of 154.5 eggs per egg mass and an 83.7% fertility rate. Investigation of intraspecific competition revealed pupation and adult eclosion was highest with 1 C. lebetis larva per hydrilla stem tip. Evaluation of the impact of C. lebetis larvae feeding on hydrilla showed stem tips in treatments with C. lebetis larvae experienced 38% higher damage compared to stem tips in control treatments. Overall, this study provided valuable information useful in improving the mass rearing of C. lebetis and predicting the damage caused by C. lebetis. For example, for efficient mass rearing, an average of 1 larva per hydrilla tip should be maintained with the remainder of eggs being used for augmentative releases.

Accurate model construction of deformed aero-engine blades for remanufacturing

Remanufacturing for aero-engine blades is an essential operation in current aerospace maintenance industry due to the significant cost savings involved. However, the individual geometric deformation in the damaged blades makes it very difficult to repair them automatically due to the lack of a model for the deformed blade. This paper proposes a new method to adaptively construct an accurate deformed blade model for remanufacturing by finding the deformation rule between the nominal blade model and the measured data collected from the deformed blade via scanning. Considering the precision of the scanned data, the flat regions of the scanned data and nominal model (suction face and pressure face) are segmented and extracted first. To achieve accurate matching results, the segmented scanned data are matched with the segmented nominal model by maintaining local rigidity under the optimal ICP (iterative closest point) framework. Then, the nonflat regions of the nominal model (leading edge and trailing edge as well as the damaged region) are stitched with the scanned data at selected fixed locations to construct the deformed blade model. A twisted compressor blade with some tip damage was selected in the case study to demonstrate the effectiveness of the proposed method. A reference deformed blade model acquired by a computational fluid dynamics software tool was utilized for comparison, and machining simulation was carried out to verify the remanufacturing result.

A new asymptotic crack tip model to predict failure processes

A two dimensional finite element asymptotic crack tip model (ABAQUS® code) to simulate crack tip opening displacement (CTOD) and damage in ductile materials has been developed. Pure Mode I is considered with asymptotic displacements applied on the outer boundary of the finite element mesh constructed using plane strain solid and cohesive elements. CTOD profiles and damage variation along cohesive element path are clearly observed. Evolution of CTOD for various ratios of solid/cohesive Young´s Modulus are also presented. The evolution of damage was based on a power law fracture criterion. In an effort to extend isotropic hardening plasticity theory to small scales, the research was focused on room-temperature crack growth in polycrystalline Aluminium alloys. In a future work, stress enhancement will be considered in a framework of cohesive zone modeling and strain gradient plasticity based on the micromechanics of dislocations. An asymptotic crack tip micro structured mesh will be also accounted into the finite element analysis.

Process Development for Tip Repair of Complex Shaped Turbine Blades with IN718

One of the most common defects during the operation of turbine blades is wear of the blade tip, which can lead to scrap of the blades. Additive Manufacturing (AM) offers the possibility to avoid a cost-intensive replacement of the complete blade with repair processes via Laser Material Deposition (LMD, also known as Direct Energy Deposition, DED) processes. Due to the industrial relevance of the application, only limited information regarding the exact deposition strategy and the process parameters used for the LMD process is available. The blade geometry used in this study is characterized by the variation of the profile cross-sections over the height of the blade. In addition, the profiles are rotated around the center of their skeleton line, which is known as twist. Furthermore, the profiles are shifted along their tendon line towards the leading edge, which is referred to as the forward sweep. First, a suitable set of process parameters is determined with which pore- and crack-free basic probes with IN718 can be manufactured. In order to transfer these parameters to the turbine blade, various process strategies are investigated which take into account both the sensitive blade geometry and the kinematics of the production system used. These strategies include the adjustment of contour and hatch tracks, design of suitable fly-in and fly-out strategies, as well as measures for the production of the overhang. The shape accuracy after the process is assessed by comparing the repaired blade with its target geometry with optical measurements. In summary, the three-dimensional build-up strategy used enables a stable reproduction of the twist and forward sweep and achieves a sufficient oversize for machining. Thus, the developed process represents a basic solution for the near-net-shape repair of blade tip damage of complex blade geometries, which can be applied to other blade geometries.

Investigation of damage mechanisms of polyethylene film during stable crack growth

In this research the fracture behavior of medium density polyethylene (MDPE) films has been evaluated using the essential work of fracture method. Also damage mechanisms of MDPE have been investigated by scanning electron microscopy and transmission optical microscopy. The results show that the EWF approach could provide a reliable toughness assessment for MDPE. Some birefringence was observed when the crack tip deformation zone was examined under cross-polarized light indicating that extensive shear yielding has occurred in front of the crack tip. It is found that shear yielding is the most effective energy absorbing mechanism in MDPE films. Microscopic evaluations also demonstrated the formation of shear bands and craze-like deformation bands in the crack tip damage zone.

Retrieval of Glass Fiber Post Using Er:YAG Laser and Conventional Endodontic Ultrasonic Method: An In Vitro Study.

To compare the times and temperatures used to remove a glass fiber post from an endodontically treated tooth using erbium-doped yttrium aluminum garnet (Er:YAG) compared to conventional endodontic ultrasonic method. Thirty-four single-root human extracted teeth were endodontically treated ex vivo. The post space was prepared to 7 mm in depth and a 11.4 mm glass fiber post was cemented using composite resin cement. Specimens were kept in 100% humidity for 24 hours and then randomly assigned to Er:YAG laser or ultrasonic methods for post removal. The removal time was recorded. Specimens with a fractured post during the removal process were excluded. The temperature on the external surface of the root was measured at the coronal, middle, and apical third portions during the laser or ultrasonic applications from 1 to 10 minutes. Data were analyzed using one-tailed t-test and paired t-test (ɑ = 0.01) for the post removal time and temperature difference, respectively. The specimen surfaces were examined using scanning electron microscopy (SEM). Fifteen specimens were tested in each group. Four specimens were fractured, 2 in the laser and 1 in ultrasonic group. One post was excluded because of laser tip damage. The average removal time were 98 ± 46.1 seconds for Er:YAG laser and 538 ± 215.6 seconds or ultrasonic groups with significant difference between the groups (p < 0.001). The temperature (°C) ranges measured from 1 to 10 minutes were [24.2°, 27.3°] for laser and [33.0°, 38.0°] for ultrasonic in the cervical area, [22.1°,24.6°] for laser and [31.0°, 34.6°] for ultrasonic in the middle area, and [24.4°, 27.7°] for laser and [30.3°, 34.1°] for ultrasonic in the apical area. There were significant differences between temperatures for each treatment (p < 0.001). SEM examination showed no visible damage caused by treatment with Er:YAG laser. Er:YAG laser can remove posts up to 5 times faster than ultrasonic removal method. The laser causes lower temperature increase at the root surface compared to the ultrasonic removal. Er:YAG may be considered as a viable alternative to sonication for post removal.

Natural fractures in tight-oil sandstones: A case study of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin, China

Natural fractures are important storage spaces and fluid-flow channels in tight-oil sandstones. Intraformational open fractures are the major channels for fluid flow in tight-oil sandstones. Small faults may provide fluid-flow channels across different layers. According to analogous outcrops, cores, and borehole image logs, small faults and intraformational open fractures are developed in the tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin, China. Among them, high dip-angle intraformational open fractures are the most abundant. Northeast-southwest–trending fractures are the principal fractures for fluid flow because that is the present-day maximum horizontal compressive stress direction. Combined with production data, horizontal wells, striking normal to or at a large angle relative to the major flow pathways, are beneficial for tight-oil production improvement. Fractures with high dip angles are the main factor that influences initial oil production. Linkage and tip damage zones are more favorable for oil production improvement than wall damage zones. This study provides an example of natural fracture characterization and unravels fracture contributions to reservoir physical properties and oil production of tight-oil sandstones, which could provide a geological basis for oil exploration and development in tight sandstones.

Fabrication of Hollow Metal Microneedle Arrays Using a Molding and Electroplating Method

ABSTRACT:The need for hollow microneedle arrays is important for both drug delivery and wearable sensor applications; however, their fabrication poses many challenges. Hollow metal microneedle arrays residing on a flexible metal foil substrate were created by combining additive manufacturing, micromolding, and electroplating approaches in a process we refer to as electromolding. A solid microneedle with inward facing ledge was fabricated with a two photon polymerization (2PP) system utilizing laser direct write (LDW) and then molded with polydimethylsiloxane. These molds were then coated with a seed layer of Ti/Au and subsequently electroplated with pulsed deposition to create hollow microneedles. An inward facing ledge provided a physical blocking platform to restrict deposition of the metal seed layer for creation of the microneedle bore. Various ledge sizes were tested and showed that the resulting seed layer void could be controlled via the ledge length. Mechanical properties of the PDMS mold was adjusted via the precursor ratio to create a more ductile mold that eliminated tip damage to the microneedles upon removal from the molds. Master structures were capable of being molded numerous times and molds were able to be reused. SEM/EDX analysis showed that trace amounts of the PDMS mold were transferred to the metal microneedle upon removal. The microneedle substrate showed a degree of flexibility that withstood over 100 cycles of bending from side to side without damaging. Microneedles were tested for their fracture strength and were capable of puncturing porcine skin and injecting a dye.

The fickle activity of a fly and a moth: variation in activity of two biocontrol agents of Chrysanthemoides monilifera

Biocontrol agents released to control exotic pests may not have the same spatial distribution as the pest species and may therefore vary in efficacy across the exotic range. These changes in distribution are unlikely to be known until species have had time to fill all preferred niches in the invasive habitat. However, studies of post-release activity of biocontrol agents rarely assess longer-term patterns of establishment in the landscape. Comostolopsis germana and Mesoclanis polana were released to control Chrysanthemoides monilifera spp. rotundata (bitou bush) between 29 and 32 years ago. We assessed their activity in foredune and hinddune habitats of coastal beaches across the major distribution of bitou bush and experimentally assessed the effectiveness of C. germana at preventing flowering and seed set. Both biocontrol agents were found to be distributed along the 870 km of coastline, representing the core area of infestation. Tip damage by C. germana was highly variable but was consistently more effective in the foredune. Comostolopsis germana was found to reduce flower production from 15 to 59% with tip damage increasing with latitude. Mesoclanis polana did not show differences in activity with latitude and only showed a marginal increase in activity in hinddunes. Comostolopsis germana and M. polana are reducing the reproductive output of bitou bush but are unlikely to be effective as a sole management strategy particularly in warmer latitudes where more seeds are released.

Comparison between Different Rotary Mowing Systems: Testing a New Method to Calculate Turfgrass Mowing Quality

Poor quality in turfgrass mowing is highlighted by the shredded leaf tips with necrotic tissues that give an unsightly brownish colour to the turf and may also lead to turf disease. Mowing quality is also typically assessed by visual rating, thus the score depends on the person doing the assessment. To make the evaluation of mowing quality not subjective, an innovative method was developed. The aim of the trial was to examine the effects of different mowing systems and two different nitrogen rates (100 and 200 kg ha−1) on two turfgrass species in order to test the new mowing quality calculation. Three different mowing systems were used: a battery-powered rotary mower set at 3000 rpm and 5000 rpm respectively and a gasoline-powered rotary mower set at full throttle. The battery-powered mower at low blade rpm produced a poorer mowing quality and turf quality than the gasoline-powered mower and battery-powered mower at high rpm, which produced a similar mowing quality and turf quality. Leaf tip damage level values showed a significant correlation with the results of the visual mowing quality assessment. Lower leaf tip damage level values (slightly above 1) corresponded to higher visual mowing quality scores (around 8).

Response relationship between loading condition and corrosion fatigue behavior of nickel-aluminum bronze alloy and its crack tip damage mechanism

Corrosion fatigue is one of the major forms for nickel‑aluminum bronze alloy used in marine propeller. It is greatly important to understand the corrosion fatigue behavior of nickel‑aluminum bronze alloy in seawater for the purpose of improving the service life of marine equipment. In this study, corrosion fatigue crack growth rate of nickel‑aluminum bronze alloy in 3.5% NaCl solution was tested under various stress intensity factors, stress ratios and loading frequencies to reveal its corrosion fatigue mechanism. The results show that corrosion environment significantly accelerates the crack growth and decreases the corrosion fatigue threshold, which is attributed to the corrosion reactions between the metals of crack tip and corrosive medium. Among the various factors, loading frequency has more predominant influence on the corrosion fatigue crack growth rate of nickel‑aluminum bronze alloy, which can be rationally explained by the hydrogen embrittlement mechanism. Additionally, in the process of corrosion fatigue crack growth, the acidification and the dealumination would occur at the crack tip, resulting in the corrosion dissolution of κ phases and the deterioration in mechanical properties of crack tip.

On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

The effect of Nb/Ti ratio on environmentally-assisted crack growth of three prototype Ni-based superalloys is studied. For these alloys, the yield strength is unaltered with increasing Nb/Ti ratio due to an increase in grain size. This situation has allowed the rationalization of the factors influencing damage tolerance at 700 °C. Primary intergranular cracks have been investigated using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope and the analysis of electron back-scatter diffraction patterns. Any possible detrimental effect of Nb on the observed crack tip damage due to Nb-rich oxide formation is not observed. Instead, evidence is presented to indicate that the tertiary γ′-precipitates are dissolving ahead of the crack consistent with the formation of oxides such as alumina and rutile. Our results have implications for alloy design efforts; at any given strength level, both more and less damage-tolerant variants of these alloys can be designed.

A study of mode-I self-similar dynamic crack propagation using a lattice spring model

The spontaneous crack growth in an infinite domain is studied using the distinct lattice spring model (DLSM). The kinetic energy, strain energy, crack opening, and crack branching during the crack growth are investigated numerically using a simple spring model. The discrete simulation satisfactorily reproduces the experimental observations and the theoretical predictions of the fracture energy increase even without considering the crack tip damage zone and crack bifurcation. Moreover, from analysis of the intrinsic fracture energy release rate, it was concluded that the observed fracture energy increase should originate from the distribution of kinetic energy during self-similar crack growth.

Remnant Trees in Enrichment Planted Gaps in Quintana Roo, Mexico: Reasons for Retention and Effects on Seedlings

Natural forest management in the tropics is often impeded by scarcity of advanced regeneration of commercial species. To supplement natural regeneration in a forest managed by a community in the Selva Maya of Mexico, nursery-grown Swietenia macrophylla seedlings were planted in multiple-tree felling gaps, known as bosquetes. Remnant trees are often left standing in gaps for cultural and economic reasons or due to their official protected status. We focus on these purposefully retained trees and their impacts on planted seedlings. Sampled bosquetes were 400–1800 m2, of which remnant trees covered a mean of 29%. Seedling height growth rates over the first 18 months after out-planting more than doubled with increased canopy openness from 0.09 m year−1 under medium cover to 0.22 m year−1 in full sun. Liana infestations and shoot tip damage were most frequent on seedlings in the open, but, contrary to our expectations, height growth rates were 0.14 m year−1 faster for liana-infested seedlings than non-infested and did not differ between damaged and undamaged seedlings. Apparently the more rapid height growth of well-illuminated seedlings more than compensated for the effects of lianas or shoot tip damage. Despite the abundance of remnant trees and their negative effects on seedling growth, enrichment planting in bosquetes has potential for community-based natural forest management in the tropics in supplementing natural regeneration of commercial species. One obvious recommendation is to leave fewer remnant trees, especially those of commercial species that are non-merchantable due to stem defects and trees retained for no apparent reason, which together constituted half of the remnant crown cover in the sampled bosquetes. Finally, given the rapid growth of lianas and understory palms in large canopy gaps, at least the most vigorous of the planted seedlings should be tended for at least two years.

5.6 W monolithic fiber laser at 3.55 μm.

We report, to the best of our knowledge, the first monolithic erbium-doped fluorozirconate fiber laser bounded by two fiber Bragg gratings (FBGs) operating at 3.55μm. Its output power and total optical efficiency are 5.6W and 26.4% respectively, the highest ever achieved at this wavelength from a fiber laser. The monolithic design of the cavity also increases its stability and prevents fiber tip damage which has limited prior demonstrations to a maximum output power of 1.5W. This Letter also studies the performances of the laser cavity for various output FBG reflectivities and presents numerical modeling results exhibiting remarkable agreement with experimental results.

In planta genotoxicity of nZVI: influence of colloidal stability on uptake, DNA damage, oxidative stress and cell death.

Nanoremediation of soil, ground and surface water using nanoscale zerovalent iron particles (nZVI) has facilitated their direct environmental exposure posing ecotoxicological concerns. Numerous studies elucidate their phytotoxicity in terms of growth and their fate within the plant system. However, their potential genotoxicity and cytotoxicity mechanisms are not known in plants. This study encompasses the physico-chemical characterisation of two forms of nZVI (nZVI-1 and nZVI-2) with different surface chemistries and their influence on uptake, root morphology, DNA damage, oxidative stress and cell death in Allium cepa roots after 24 h. To our knowledge, this is the first report on the cyto-genotoxicity of nZVI in plants. The adsorption of nZVI on root surfaces caused root tip, epidermal and root hair damage as assessed by Scanning Electron Microscopy. nZVI-1, due to its colloidal destabilisation (low zeta potential, conductivity and high polydispersity index), smaller size and high uptake imparted enhanced DNA damage, chromosome/nuclear aberrations (CAs/NAs) and micronuclei formation compared to nZVI-2. Although nZVI-2 exhibited high zeta potential and conductivity, its higher dissolution and substantial uptake induced genotoxicity. nZVI incited the generation of reactive oxygen species (ROS) (hydrogen peroxide, superoxide and hydroxyl radicals) leading to membrane lipid peroxidation, electrolyte leakage and mitochondrial depolarisation. The inactivation of catalase and insignificant glutathione levels marked the onset of oxidative stress. Increased superoxide dismutase and guaiacol peroxidase enzyme activities, and proline content indicated the activation of antioxidant defence machinery to alleviate ROS. Moreover, ROS-mediated apoptotic and necrotic cell death occurred in both nZVI-1 and nZVI-2-treated roots. Our results open up further possibilities in the environmental safety appraisal of bare and modified nZVI in correlation with their physico-chemical characters.

Variations in thickness of fault-controlled dikes and its implications: A case study of Gosung area, South-East Korea

Dikes are natural records that can be used to understand the way magma flows in the crust. Coastal platform outcrops in Gosung, South Korea, show clear evidences that their intrusion took place along pre-existing fractures. We analyzed outcropping dikes, measuring variations in dike thickness as well as fracture density (cumulative number of fractures along strike) and geometry around the dikes. The geometry and thickness variations of dikes intruded along pre-existing fractures can be interpreted to understand the effect of pre-existing fractures to evolution on magma flow, especially related with fault damage zones. This helps us to gain a better understanding of magma and fluid flow along pre-existing fractures. Magma flow is greater along planes that strike perpendicular to the direction of least compressive horizontal stress, and along well connected fractures that show a high degree of connectivity. At the fault tip and linkage damage zone, there is a concentration of extensional fractures; in these areas injected dikelets can form. As faults become linked, the fracture density increases, until they become fully linked and act as one through-going fault plane. As faults evolve, the boundary conditions of the faults vary and this has an impact on dike characteristics. Fracture geometry around dikes that intruded pre-existing faults can be used as a record of fault evolution and this can give insights into how the maturity of a fault system can affect to the related magma or fluid flow characteristics. 韓国南東部の固城地域の波食台に露出する，母岩の既存の亀裂内に貫入した岩脈の厚さと岩脈周辺の母岩中の割れ目の数密度や形状を解析した．既存の割れ目に貫入した岩脈の形状や厚さの変化はマグマ貫入に対する既存の割れ目の影響を示している.マグマ貫入量は水平最小圧縮軸方向に垂直な割れ目に沿って最大となり，また連結した割れ目ほど大きい．断層の先端部やダメージゾーンには開口割れ目が集中して形成されており，そこではマグマが注入して形成された小岩脈がみられる．断層が連結するにつれて周辺の母岩内の亀裂数密度は増加し，断層が完全に連結して一連の断層としてふるまうようになるまで増加し続ける．断層成長につれて断層の境界条件は様々に変化し，それが既存の割れ目に貫入する岩脈にも影響を与える．岩脈周辺の割れ目の構造は断層の成長過程の記録であり，マグマや流体の移動に対する断層システムの成熟過程の影響を示している.

Effects of Carriers, Emulsifiers, and Biopesticides for Direct Silk Treatments on Caterpillar Feeding Damage and Ear Development in Sweet Corn.

In the northeastern United States, control of Lepidopteran pests of sweet corn, particularly corn earworm [Helicoverpa zea (Boddie)], is difficult using organic methods. The direct application of corn oil and Bacillus thuringiensis (Bt) to corn silk has been shown to reduce ear damage from corn earworm in past studies; these studies sought to optimize this method by evaluating additional carrier and biopesticide mixtures that comply with the United States Federal Insecticide, Fungicide, and Rodenticide Act and National Organic Standards. Carriers, which are liquids used to dissolve the biopesticide and deliver it into the tip of the ear, may have phytotoxic or insecticidal properties. Experiments conducted from 2001 to 2005 evaluated caterpillar damage and ear development effects from carriers (vegetable and paraffinic oils and carrageenan), biopesticides (Bt, spinsosad, and neem), and three emulsifiers in various combinations when applied directly to the tips of the ears 5-7 d after silk initiation. There were no effects of emulsifiers on ear quality, except for slight reduction in caterpillar damage in one of the two years. There were no differences among corn, soy, canola, and safflower oils in corn earworm control or tip development. The carrageenan carrier had the least effect upon ear development as measured by the length of nonpollinated kernels at the tip, compared to corn oil or paraffinic oil (JMS Stylet Oil), which caused the greatest tip damage as well as an oily discoloration. The carrier-pesticide combinations with the best ear quality overall were spinosad in carrageenan or corn oil, and Bt in carrageenan.