Confocal Laser Research Articles

Lateral growth rate of δ phase during solidification of Fe-0.15wt%C-0.8wt%Mn steel

Taking Fe-0.15wt%C-0.8wt%Mn steel as the research object, in situ observations of the δ phase growth process during solidification were conducted by using a high-temperature confocal scanning laser microscope (HTCSLM). The effects of the solid/liquid (S/L) interface’s shape, temperature, and curvature radius on the lateral growth rate of δ phase were investigated in detail, and the relational expression among the lateral growth rate of δ phase, temperature, and curvature radius of column-shaped δ phase was deduced for the carbon steel during solidification. The results indicate the growth rate of the concave-shaped S/L interface is larger than that of the convex-shaped S/L interface during the beginning growth of δ phase, but these two kinds of growth rates gradually approach with proceeding in solidification. The calculated lateral growth rate of δ phase is consistent with the experimental result at a cooling rate of 0.045°C/s.

Importance of structural integrity of somatic embryos for long-term cryopreservation of cocoa (Theobroma cacao L.) germplasm

Cryopreservation is a reliable means for the long-term conservation of plant genetic resources. It is of particular interest for cocoa (Theobroma cacao L.) whose seeds are recalcitrant to conventional storage methods and field collections susceptible to disease infestations. However, the encapsulation- dehydration procedure previously developed for cocoa somatic embryos has resulted in poor survival after retrieval from liquid nitrogen. To examine the causes of such failure, cocoa somatic embryos following each treatment step of the encapsulation-dehydration procedure were examined using a combination of confocal scanning laser microscopy and transmission electron microscopy. Results showed that the parenchyma’s cells of the hypocotyl and radicle were the major sites of injury possibly due to their large size and non-cytoplasmic nature, whereas the shoot meristem and provascular strand were well preserved throughout the treatments. In general, cell deformation and/or disruption was observed following the sucrose preculture, desiccation and freezing steps, with the extent of damage increasing at each treatment step. Post-thaw regrowth of injured embryos was possible through the proliferation of surviving cells, but these embryos often failed to convert into plantlets. The present study suggests that the maintenance of structural integrity of somatic embryos at each treatment step is essential for the successful cryopreservation of cocoa germplasm. Key words: Cocoa somatic embryos, confocal scanning laser microscopy, cryopreservation, structural integrity, transmission electron microscopy.

Topographic Differences between Large and Normal Optic Discs: A Confocal Scanning Laser Ophthalmoscopy Study

The aim of the study was to investigate the optic nerve head parameters of healthy macrodiscs to provide standard measurements for them to be the basis for future quantitative comparisons. Sixty-nine subjects with macrodisc (disc area larger than 2.82 mm(2)) and 91 healthy controls (disc area between 1.16 and 2.82 mm(2)) were recruited. After a complete ophthalmic examination, confocal scanning laser ophthalmoscopy was performed in all participants. The stereometric parameters of confocal scanning laser ophthalmoscopy examination and the proportion of subjects classified as normal, borderline, and glaucomatous by the Moorfield Regression Analysis were compared between groups. A total of 160 subjects were included in the study. The average disc sizes in the control and macrodisc groups were 2.14 ± 0.33 mm(2) and 3.36 ± 0.36 mm(2), respectively. Cup area (p<0.001), rim area (p=0.01), cup volume (p<0.001), cup/disc area ratio (p<0.001), linear cup/disc ratio (p<0.001), mean cup depth (p<0.001), maximum cup depth (p<0.001), and cup shape measure (p<0.001) differed significantly between the 2 groups. The parameters of the optic nerve head which did not differ significantly between groups were rim volume (p=0.17) and height variation contour (p=0.88). A significantly higher number of eyes were erroneously identified as abnormal (15.1% vs 79.4%) by Moorfield Regression Analysis in the macrodisc group (p<0.001). Rim volume and height variation contour were the only optic nerve head topographic parameters that were similar in eyes with large and normal disc sizes. They seem to be promising parameters in the evaluation and comparison of the optic nerve head of subjects with macrodisc.

Control of Liquid-Drop Surface Shape in Melt

The carbon steel samples of great quality can not be melted using a high-temperature confocal scanning laser microscopy(HTCSLM). On account of only arc surface of the tiny liquid-drop top is observed, it is difficult to obtain distinct images. The shape variation of the tiny liquid-drop is studied experimentally in this article. The results show that the shape of the liquid-drop will be changed at 1600°C, when the carbon steel sample of 0.5g is laid on the Al2O3sloping of 15 degrees. Though the radius of curvature of the liquid-drop top surface is obviously enlarged, the impact of improving the surface shape of liquid-drop through the gravity flow of tiny liquid-drop is finite. For the carbon steel sample of less than 0.8g, the hanging drop is automatically formed in the melting process under the condition that the gap between the solid sample and Al2O3single crystal plate is 0.3mm, and the shape retains invariant when it is hold for 20 min at 1600°C. The contact surface between the sample and Al2O3single crystal plate is 24mm2.

&lt;i&gt;In Situ&lt;/i&gt; Observation of Solidification Behavior in a Q235 Steel by Using Electric Pulse Modification

In the unmodified and EP-modified melt of Q235 steel, the solidification behavior including the nucleation and growth of crystals has been observedin situby use of a confocal scanning laser microscope combined with an infrared image furnace, and meanwhile, described the characteristic of phase transformation. The result shows that the every stage of phase transformation is advanced; the phase transformation time is shortened, and temperature is reduced during heating proceeds. On the other hand, it can be observed that the nucleation density of solid phase increases and has an even distribution among the liquid phase.

Endothelin 1 Stimulates Ca2+-Sparks and Oscillations in Retinal Arteriolar Myocytes via IP3R and RyR-Dependent Ca2+Release

To investigate endothelin 1 (Et1)-dependent Ca(2+)-signaling at the cellular and subcellular levels in retinal arteriolar myocytes. Et1 responses were imaged from Fluo-4-loaded smooth muscle in isolated segments of rat retinal arteriole using confocal laser microscopy. Basal [Ca(2+)](i), subcellular Ca(2+)-sparks, and cellular Ca(2+)-oscillations were all increased during exposure to Et1 (10 nM). Ca(2+)-spark frequency was also increased by 90% by 10 nM Et1. The increase in oscillation frequency was concentration dependent and was inhibited by the EtA receptor (Et(A)R) blocker BQ123 but not by the EtB receptor antagonist BQ788. Stimulation of Ca(2+)-oscillations by Et1 was inhibited by a phospholipase C blocker (U73122; 10 μM), two inhibitors of inositol 1,4,5-trisphosphate receptors (IP(3)Rs), xestospongin C (10 μM), 2-aminoethoxydiphenyl borate (100 μM), and tetracaine (100 μM), a blocker of ryanodine receptors (RyRs). Et1 stimulates Ca(2+)-sparks and oscillations through Et(A)Rs. The underlying mechanism involves the activation of phospholipase C and both IP(3)Rs and RyRs, suggesting crosstalk between these Ca(2+)-release channels. These findings suggest that phasic Ca(2+)-oscillations play an important role in the smooth muscle response to Et1 within the retinal microvasculature and support an excitatory, proconstrictor role for Ca(2+)-sparks in these vessels.

Characteristics of fundus autofluorscence in patients with atrophic age-related macular degeneration

Background The early diagnosis and treatment is vital for the age-related macular degeneration (AMD).Previous examining methods were fundus fluorescein angiography(FFA)and optical coherence tomography (OCT).However,a new diagnostic technique,fundus autofluorescence(FAF),is applying in ophthalmology.objective This study was to observe the FAF characteristics of atrophic AMD. Methods Thirty-nine eyes of 28 patients with atrophic AMD were diagnosed and collected in our hospital and classified based on the criteria of Chen Song.FAF was performed by a confocal scanning laser ophthalmoscope(Heidelberg Retina Angiograph 2,HRA2).Characteristics of FAF images were compared with FFA images or color fundus photographs.Written informed consent was obtained from each patient prior to the examination. Results Areas with abnormal increased or decreased FAF signals were consisted or unconsisted with funduscopically visible alterations.Seven manifestations of FAF were found in the eyes with preatrophic stage of atrophic AMD,including slight change,focal increase pattern,patchy pattern,linear pattern,lacelike pattern,reticular pattern,and speckled pattern.In atrophic stage of atrophic AMD,geographic atrophy showed a well-defined hypoautofluorescence area;while non-geographic atrophy showed a ill-defined hypoautofluorescence area.There were three abnormal FAF patterns(focal,band and diffuse)in the junctional zone of geographic atrophy and diffuse pattern in the junctional zone of non-geographic atrophy. Conclusion FAF imaging is helpful for the diagnosis of atrophic AMD as a new non-invasive technique. Key words: Age-related macular degeneration; Confocal Scanning Laser Ophthalmoscope; Fundus autofluorescence; Atrophic age-related macular degeneration

Biofilm formation of Ureaplasma urealyticum and its relationship with drug resistance

Objective To study the ability of standard strain and clinical isolates of Ureaplasma spp. to form biofilms in vitro and to compare the antibiotic susceptibility of sessile cells and their planktonic counterparts. Methods A total of 21 Ureaplasma wealyticum(Uu) isolates recovered from female patients diagnosed with cervicitis and Uu serovar 3 and Uu serovar 8( Uu3, Uu8) were included. Scanning electron microscope and confocal scanning laser microscopy were used to identify biofilm formation. Conventional antibiotic susceptibility tests and biofilm susceptibility assays for tetracycline, erythromycin and ciprofloxacin were carried out. The paired rank sum test and was applied to analyze the statistical differences between the MIC and the minimal biofilm inhibitory concentration. The x2 test was applied to analyze the statistical differences of global resistance percentages between planktonic cells and sessile cells. Results Uu3, Uu8 and 21 Uu isolates all can form biofilms in vitro. Minimal inhibitory concentration of sessile cells compared with planktonic cells were obviously higher for tetracycline, erythromycin and ciprofloxacin (P <0.001). Global resistance percentages between planktonic cells and sessile cells were different for erythromycin (9.52% vs 61.90% , P < 0. 001), ciprofloxacin ( 80. 95% vs 100% , P = 0. 035 ) and tetracycline (4. 76% vs 14.29% , P =0.293). Conclusion Uu isolates and Uu1, Uu8 all can form biofilms in vitro, and biofilm formation can strengthen resistance of Uu to antibiotics, even multidrug resistance was observed. Key words: Ureaplasma urealyticum; Biofilms; Multidrug resistance

Quantitative study of fundus autofluorescence distribution at the posterior pole in normal subjects

Objective To observe the characteristics of fundus autofluorescence （AF） distribution at the posterior pole in normal subjects. Methods Seventy-nine normal subjects （156 eyes） were studied. Confocal scanning laser ophthalmoscope （cSLO） HRA2 was used to obtain the AF average image at the posterior pole. The distance was calibrated by Digimizer image analysis system. With umbo as the center, the macula was divided into foveola, fovea, parafovea and perifovea areas which with the radius 175, 750, 1250 and 2750 μm respectively. Each area was further divided into inferior, superior, temporal and nasal quadrants by two radial lines angle of 90°, except for foveola. The AF intensity in four quadrants of different macular regions and optic disc were measured. The AF intensity in vertical and horizontal direction of umbo was also measured. Then the effects of age, eyes, and gender on AF intensity in four quadrants of different macular regions were analyzed. Results There were statistically significant differences in AF intensity among optic disc and four quadrants of macular regions （F=528. 648, P〈0.05）. AF distribution was V-type in vertical direction and M-type in horizontal direction. There were statistically significant differences between age groups in foveola, inferior parafovea, temporal parafovea, inferior perifovea, superior perifovea and temporal perifovea （P〈 0.01）. There were no statistically significant differences between the two eyes （P〉0.05）. Between genders group, there were statistically significant differences in foveola, superior fovea, inferior fovea, nasal fovea and temporal perifovea （P〈0.05）; no statistically significant differences in the other quadrants （P〉0.05）. Conclusions The distribution of AF intensity is inhomogeneous in macular regions and four quadrants of each region in normal subjects. AF intensity increases with aging. AF distribution is symmetrical in both eyes. There is probably no correlation between gender and AF intensity distribution. Key words: Retinal pigments/diagnostic use; Lipofuscin/analysis; Microscopy, confocal/ methods; Image processing, computer-assisted; Pigment epithelium of eye/metabolism

Clinical application of Optovue RTVue OCI' and Heidelberg Retina Tomograph III in early diagnosis of glaucoma

Background Many studies showed that attenuation of retinal nerve fiber layer(RNFL)in early glaucoma is one of the important signs.How to accurately and quantitatively measure RNFL thickness is very important for the early diagnosis and monitoring of glaucoma.0bjective This study was to evaluate the clinical value of Optovue RTVue OCT and Heidelberg Retina Tomograph Ⅲ(HRT-Ⅲ)confocal scanning laser ophthalmoscopy in glaucomatous eyes. Methods This cross-sectional study included 40 eyes of 26 patients with suspected open-angle glaucoma(SOAG),48 eyes of 29 patients with open-angle glaucoma and 48 eyes of 27 healthy subjects.Optical nerve head(ONH) parameters and peripapillary RNFL thickness were measured in all the subjects with Optovue RTVue OCT and HRT-Ⅲ,meanwhile all the eyes received perimetry with Humphrey 750-I.Glaucoma variables obtained from Optovue RTVue OCT and HRT-Ⅲ were analyzed among the groups.Topographic Optovue RTVue OCT and HRT-Ⅲ parameters,including disc area(DA),cup area(CA),rim area(RA),rim volume(RV),cup volume(CV),cup/disc area ratio(C/DAR)as well as superior,temporal,inferior and nasal average RNFL thickness,were analyzed.The relationship of ONH parameters and RNFL thickness was analyzed using a linear correlation.The correlation between the mean defect(MD)of the visual field and the tomography parameters in glaucomatous eyes was described by bivariate Pearson correlation coefficients.Resuits The ONH parameters and RNFL thickness obtained by HRT-Ⅲ and OCT showed significant difference(P<0.05).ONH parameters such as RA,C/DAR,CA and RV were statistically changed in SOAG and the POAG patients compared with the normal subjects(q=6.47,q=7.67,P<0.05).The superior and inferior RNFL thickness parameters in three groups were positively correlated between HRT-Ⅲand OCT(r=0.362,r=0.441,r=0.395,P<0.05),Topographic Optovue RTVue OCT and HRT-Ⅲ parameters including CV,CA,RA and C/DAR fitted Pearson analysis(all P<0.05).In POAG group。The RA,RV,CV,C/DAR from Optovue RTVue OCT were correlated with MD with the significant coefficient 0.284,0.286,0.340,0.371 respectively(P<0.05),and evidently correlations also were found between RA,RV,C/DAR with MD respectively with the coefficient 0.339,0.859,0.422(P<0.05)by HRT-Ⅲ. Conclusion Both Optovue RTVue OCT and HRT-Ⅲ can difierentiate ONH analysis with a similar outcome in glaucomatous eye.The C/D value.RA,superior and inferior RNFL thickness based on Optovue RTVue OCT and HRT-Ⅲare distinguishing indexes in the diagnosis of early glaucomatous damage. Key words: Glaucoma; Optovue RTVue OCT; Heidelberg Retina Tomograph Ⅲ confocal scanning laser ophthalmoscopy; Retinal nerve fiber layer thickness; Optical disc; Perimetry

CELLO measurement technique for local identification and characterization of various types of solar cell defects

AbstractThe CELLO technique allows to measure local data for a large number of solar cell parameters like bulk life time, back side surface recombination velocity, diffusion coefficient, and serial resistance. Inhomogeneities of these parameters induce lateral current flow in forward direction, which mixes the effects of the different defect types. Even if all local parameters would be known, a complete simulation is needed to obtain information about the local efficiency. Direct CELLO measurement at e.g. the working of the solar cell or at open circuit allows extracting this combined information directly. Examples for this will be presented in this paper, dealing with multicrystalline silicon solar cells showing a variety of defect types.Mainly to save measurement time several frequencies are applied simultaneously as a Laser intensity perturbation signal and analyzed by FFT deconvolution. The frequencies can be applied simultaneously to 3 confocal Lasers with different wavelength, i.e. penetration depths. Typically 4 frequencies are analyzed simultaneusly in order to maintain a good signal to noise ratio. This features will be discussed shortly as well. Especially the application of a deep penetrating Laser significantly increases the robustness of the fitting procedure and allows to separate reliably bulk and surface recombination and mobility dependencies (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Superresolution in adaptive optics confocal scanning laser ophthalmoscope

The resolution of adaptive optics confocal scanning laser ophthalmoscope is constrained by human eye’s aberration, numberical aperture and pinhole size. A super resolved adaptive optics confocal scanning laser ophthalmoscope is presented. By using adaptive optics to detect and compensate human eye’s aberration, and using optical superresolution to improve resolution which is degraded by large pinhole size, the system can achieve high resolution, real-time human retina image in vivo .

Determinants of Agreement between the Confocal Scanning Laser Tomograph and Standardized Assessment of Glaucomatous Progression

Determinants of Agreement between the Confocal Scanning Laser Tomograph and Standardized Assessment of Glaucomatous Progression

Space Heritage: The Apollo Heat Shield; Atmospheric Reentry Imprint on Materials’ Surface

ABSTRACTThe heat shield is part of a thermal protective system (TPS) essential in shielding the cargo of a spacecraft during reentry to the earth’s atmosphere. The ablated surface of the heat shield is a testimony to the harsh reentry environment, evidenced in melting and charring among other phenomena that occur during reentry at velocity of 9-11 km/sec. The aim of this study was to extrapolate information about atmospheric reentry from the surface of the ablated material. A sample of the heat shield from the test vehicle of the Apollo Program, AS-202, was the subject of the analysis.For the preliminary studies, selected investigation modes from the Global Optimal Strategy model, developed to identify wear of engineering surfaces, were applied: examination of structure, optical observation, physico-chemical characterization and surface morphology. Instrumentation used included: microscopic surface analysis with Extended Depth of Field composite images (EDF), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR), confocal scanning laser microscopy and laser scanning microscopy. The Apollo Program testing vehicle AS-202 (1966) ablated specimen sample was obtained from the collection of the National Air and Space Museum (NASM), Smithsonian Institution, Washington DC. The authors combine their diverse experiences in tribology and in artifacts’ museum conservation so as to contribute to the space heritage material science. This study represents one of the building blocks of a larger project, the Fundamental Model of public outreach and perception (FAM-pop) of complex aerospace technologies.

Patterning Collagen/Poloxamine-Methacrylate Hydrogels for Tissue-Engineering-Inspired Microfluidic and Laser Lithography Applications

The ability to pattern semi-synthetic collagen/poloxamine-methacrylate hydrogels into straight-channel flow circuits and sub-millimeter-sized rectangular blocks for tissue-engineering applications was evaluated. Endothelial cells, grown on the surface of flat collagen/poloxamine-methacrylate hydrogels, proliferated, expressed ICAM-1 (but not VCAM-1) and began to detach after 6 days. Seeding endothelial cells onto the lumen surface of straight collagen/poloxamine-methacrylate flow channels increased ICAM-1 and VCAM-1 expression, and exposure to laminar shear stress (0.3–10 dyn/cm2) was unable to attenuate activation on the relatively few cells that were able to withstand flow associated ablation. The enrichment of poloxamine-methacrylate at the lumen surface during fabrication likely caused the decrease in cell attachment and increased activation. To micropattern more complex structures, confocal microscopy UV laser lithography was used to selectively cross-link a HepG2-containing pre-polymer solution of collagen/poloxamine-methacrylate. Turbidity (caused by suspended cells and the incomplete miscibility of collagen and poloxamine-methacrylate) scattered the UV laser energy and necessitated the optimization of exposure times with respect to cross-linking extent and cell viability. Free radical diffusion beyond the bounds of the initial photopattern reduced the resolution of the structures and created a weakly cross-linked periphery around the original pattern. Over time, HepG2 cells migrated towards the less cross-linked periphery and proliferated, creating a non-uniform distribution of cells.

Modeling of Diffusion Transport through Oral Biofilms with the Inverse Problem Method

AimThe purpose of this study was to develop a mathematical model to quantitatively describe the passive transport of macromolecules within dental biofilms.MethodologyFluorescently labeled dextrans with different molecular mass (3 kD, 10 kD, 40 kD, 70 kD, 2 000 kD) were used as a series of diffusion probes. Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum were used as inocula for biofilm formation. The diffusion processes of different probes through the in vitro biofilm were recorded with a confocal laser microscope.ResultsMathematical function of biofilm penetration was constructed on the basis of the inverse problem method. Based on this function, not only the relationship between average concentration of steady-state and molecule weights can be analyzed, but also that between penetrative time and molecule weights.ConclusionThis can be used to predict the effective concentration and the penetrative time of anti-biofilm medicines that can diffuse through oral biofilm. Furthermore, an improved model for large molecule is proposed by considering the exchange time at the upper boundary of the dental biofilm.

High pressure-induced structural effects in plastic packaging

Today, flexible vacuum packages are predominantly used for products to be subjected to high pressure treatment. However, tray packages with a modified atmosphere are in demand, which provide a high failure rate with respect to gas and water vapour permeability and packaging integrity. Methods to follow permeation processes under high pressure were developed and used together with optical microscopy, confocal scanning laser microscopy, Raman spectroscopy and atomic force microscopy to identify the mechanisms for changes in permeability and damage to the packaging materials. Single film samples and pouch packages filled with model products were studied. Results indicate a reversible decrease in the coefficients of diffusion and permeation under the impact of high pressure, due to the compression of the polymeric bulk. Irreversible changes in the polymeric materials are associated with gases in the packaging head space, which cause high local temperatures and create damage due to rapid deliberation upon the pressure drop at the end of the high pressure cycle.

Macular Retinal Ganglion Cell Complex Thickness and Its Relationship to the Optic Nerve Head Topography in Glaucomatous Eyes with Hemifield Defects

Purpose. To evaluate the relationship between the macular ganglion cell complex (mGCC) thickness, which is the sum of the retinal nerve fiber, ganglion cell, and inner plexiform layers, measured with a spectral-domain optical coherence tomograph and the optic nerve head topography measured with a confocal scanning laser ophthalmoscope in glaucomatous eyes with visual field defects localized predominantly to either hemifield. Materials and Methods. The correlation between the mGCC thickness in hemispheres corresponding to hemifields with and without defects (damaged and intact hemispheres, respectively) and the optic nerve head topography corresponding to the respective hemispheres was evaluated in 18 glaucomatous eyes. Results. The mGCC thickness was significantly correlated with the rim volume, mean retinal nerve fiber layer thickness, and cross-sectional area of the retinal nerve fiber layer in both the intact and the damaged hemispheres (P < .05). Discussion. For detecting very early glaucomatous damage of the optic nerve, changes in the thicknesses of the inner retina in the macular area and peripapillary RNFL as well as rim volume changes in the optic nerve head are target parameters that should be carefully monitored.

An Electron Microscopy Investigation of the Transient Stage Oxidation Products in an Fe-22Cr Alloy with Ce and La Additions Exposed to Dry Air at 1073 K (800 °C)

In this study, the effects of Ce (270 ppm) and La (120 ppm) mischmetal additions on the transient oxidation of an Fe-22Cr alloy were investigated. The oxidation process was imaged in situ using a confocal scanning laser microscope. The oxidation microstructures were studied by scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy with the help of focused ion beam in situ lift-out specimen preparation. The Ce and La, referred to as reactive elements, were found in nonmetallic inclusion particles in the forms of oxides, sulfides, and phosphates. An affected zone formed around rare earth (RE)-containing inclusion particles at the alloy free surface during the transient oxidation. This zone consisted of an internal Cr-oxide formed beneath the particle as well as a thinner external oxide scale on the surface compared with the surroundings. The relation of this microstructure to oxidation kinetics is discussed. With time, the RE elements diffused into the scale from the RE particles on the alloy surface during the high-temperature exposure. A diffusion mechanism is presented to describe these observations.

The influence of biaxial strain ratio and strain range on crack growth mode and crack shape

Axial-torsion tests were used to determine and model the combinations of strain range and crack length at which the crack growth changed from a shear to a tensile mode. Biaxial tests and confocal scanning laser microscopy (CSLM) were used to observe crack shape evolution at various strain ratios. Constant and variable amplitude loading of notched specimens and CSLM were used to determine the dependence of crack shape development on strain range. The results showed that, except for very high strain levels, at strain ratios causing shear mode crack growth multiple cracks initiated and grew until they were semicircular and then linked up to cause failure. For tensile mode crack growth at low strains a single crack grew into and maintained a semicircular shape. At high strain ranges multiple cracks formed and linked up to maintain an elongated crack shape.