Primary Plate Research Articles

Effect of Friction Stir Processing on the Microstructure and Mechanical Properties of A384 Aluminum Alloy

Friction stir processing (FSP) is a solid-state technique for microstructural modification. The aim of this work is to evaluate the effect of input process parameters of friction stir processing (tool rotational speed rpm, travel speed mm/min) on microstructure and mechanical properties of A384 aluminum alloy. A384 aluminum alloy was cast using conventional stir casting process. The obtained alloy was subjected to friction stir process using different input parameters (rpm, mm/min) with double pass. Water was used as cooling medium during process. The microstructures of investigated alloys were characterized by optical, SEM microscopes, EDS and Map analyzer, while mechanical properties were evaluated by using tensile test. The results indicate that; after friction stir processing, the microstructure of as-cast alloy was greatly improved. Needle-like eutectic Si and Chinese Script a-Fe were modified to fine precipitates. Meanwhile, coarse primary Si and large plate b-Fe phase were dissolved. On the other hand, mapping analysis shows homogenous distribution of different alloying elements through the matrix. The higher values of tensile properties were obtained at 1200 rpm and 80 mm/min. UTS and YS were increased by 98% and50%, respectively. Meanwhile, ductility was approximately three times higher than that of cast alloy.

PAIN AND ANTISEPSIS AFTER OCULAR ADMINISTRATION OF POVIDONE-IODINE VERSUS CHLORHEXIDINE.

To investigate ocular bacterial count before and after antisepsis with aqueous chlorhexidine (AC) or povidone-iodine (PI) and to assess discomfort with each agent. Bacterial swabs were taken from participants' eyes before and after antisepsis. These underwent microscopy, culture, and sensitivity testing. Aqueous chlorhexidine drops were administered to left eyes and PI to right eyes. Participants rated their pain (scale 0-10) for each eye but were blinded to the type of drop. There were 20 participants (17 women, 3 men), and the mean age was 43 years. Pain scores were significantly higher in right (PI) than in left (AC) eyes (mean 7 vs. mean 2, P < 0.001). No abnormalities were detected on specimen microscopy and gram staining. Seven preantisepsis swabs (three left and four right) grew bacteria in culture. Two postantisepsis swabs grew bacteria in primary culture plate (1 after AC and 1 after PI). For an additional one post-PI swab, bacteria were detected in enrichment broth only. The efficacy of AC and PI are similar, and patient discomfort is lower with AC. Aqueous chlorhexidine is a good alternative to PI for antisepsis before intravitreal injection.

Finite Element Analysis of Different Double-Plate Angles in the Treatment of the Femoral Shaft Nonunion with No Cortical Support opposite the Primary Lateral Plate

Objectives We evaluated the biomechanical outcome of different plate fixation strategies (the single plate construct, 45° double-plate construct, 90° double-plate construct, 135° double-plate construct, and 180° double-plate construct) used for the fixation of the femoral shaft nonunion with no cortical support opposite the primary lateral plate. This may help surgeons choose the optimal therapy to the femoral shaft nonunion. Methods The femoral shaft nonunion with no medial support and the models of lateral plate and medial plate was constructed in 3-matic software and UG-NX software, respectively. We then assembled the single plate and different double plates to the fracture model separately to form the fixation models. After meshing the models' elements, we used the ABAQUS software to perform the finite element analysis. Values of the von Mises Stress (VMS) distribution of the implant, peak VMS, and model displacement and deformation were used to capture the mechanical factors in this study. Results Our results indicated that the peak von Mises Stress (VMS) of the lateral plate was concentrated in middle surface of the lateral plate near the fragment of each group. The peak VMS was 5201.0 MPa (the single-plate construct), 3490.0 MPa (45° double-plate construct), 1754.0 MPa (90° double-plate construct), 1123.0 MPa (135° double-plate construct), and 816.5 MPa (180° double-plate construct). The additional short plate dispersed some stress leading to the decrease in the peak VMS of the lateral plate. As angle formed by the double plates increased, the dispersed function of the additional plate was becoming obvious. The bending angles of the lateral plate were 18° versus 12° versus 3° versus 2° versus 1° (the single-plate construct versus 45° double-plate construct versus 90° double-plate construct versus 135° double-plate construct versus 180° double-plate construct). Conclusions Our study indicated that increasing the angle between the plates in a double-plate construct improves the stability of the construct over a single lateral plate when there is no cortical support opposite to the lateral plate. The strongest fixation occurred when the angle between the two plates was greater than ninety degrees.

New insight on thecal plate development in early cambrian eocrinoids: an example from south china

ABSTRACTThe gogiid eocrinoid Guizhoueocrinus yui is the most abundant member of the marine benthos in the Balang Fauna (Cambrian Series 2, Stage 4) of Guizhou, China. To date, little attention has been paid to the morphological development of the thecal plates. Here, based on 120 specimens, we describe the morphological development of the primary large thecal plate in the widest part of the theca (WPT). These results demonstrate that the primary large thecal plates in different ontogenetic stages exhibit a unique trajectory within a space defined by size and shape. As the individual grows, the centroid size of the plates shows a continuous changing process. Moreover, the shape of the plate alters during the ontogeny: initially polygonal to oval, then develop a more sprocket-like shape. These results provide statistically supported differences among three pre-defined ontogenetic stages. However, the thecal plates show a gradual growth in seven divided sub-stages. These morphological changes prove that the margins of the primary large thecal plate in the WPT underwent a process of resorption and redeposition to produce more sutural pores. This study demonstrates that newborn sutural pores may help organism to get more oxygen for supporting individuals’ life activities.

Radiological follow up of volar locking plating of distal radius fracture

Introduction: Fracture of the distal end radius constitutes one of the most common skeletal injuries treated by an orthopaedic surgeon. This study was aimed to assess the clinical and radiological outcome of the intra-articular fracture distal end radius treated with variable angle mini-fragment volar plate fixation. Methodology: In the prospective study, patients presenting with distal end radius fracture and then operated with mini-fragment volar locking distal radius plating were included. All patients were evaluated by a senior orthopaedic surgeon at 3, 6 and 24 weeks post-operatively, during which patients underwent a physical examination of the wrist and forearm motion and grip strength, followed by radiological evaluation. Range of movement and complications were noted for all patients at each follow up visit.Results: 64% of the patients were below the age of 40 years. Approximately three fourths of all patients were classified as Frykmann distal radius fracture type VIII. The mean radial inclination, length and tilt were maintained throughout the follow up period. The range of dorsiflexion, palmarflexion, supination and pronation improved significantly at each follow up. 8% had superficial skin infection, 4% had serous discharge and loss of reduction each and 84% did not report any complications.Conclusions: Primary volar mini-fragment variable angle plate fixation of freshly displaced distal radius fracture provides complete union, with immediate mobilization, better functional outcomes, minimizes chances of delayed/malunion.

Assessment of radiological outcomes in gap non-union of long bones using non-vascularised fibular strut graft augmented with corticocancellous graft

Background: A prospective study was conducted in the department of Orthopaedics & Traumatology in Dr. D.Y Patil Hospital, Navi Mumbai from January 2015 to June 2017 to assess radiological outcomes in traumatic gap non-union of long bones after primary plate fixation failure using non-vascularised fibular strut graft augmented with corticocancellous graft. Methods: A total of 20 patients were included in study presenting with non-union of humerus. In 13 males and 7 females, age between 18-65 years (average 41 years), were operated using non-vascularized fibular strut graft taken from ipsilateral site augmented with auto corticocancellous graft. All the patients were operated by same surgeon with removal of previous plate and fixing with re-plating and intramedullary fibular grafting. The mean follow-up was 9 months (range 6-12 months). The patients were assessed for functional range of motion along with x-ray. Union was achieved after confirming on x-ray. Observations & Results: In study 20 patients there were 13 males and 7 females with average age being 41.35 yrs, average length of fibular graft was 6.3 cm and mean duration of union 21.15 weeks.1 patient was lost in follow up and none of patients showed non union or secondary intervention thus ensuring Bony union in all 20 patients treated with graft and plating Conclusion: This procedure successfully showed that union at nonunion site with adequate vascularity and good soft tissue coverage can be achieved with proper patient selection and using fibular graft in addition to traditional plating and CC graft technique. Even though procedure is lengthy but it’s simplicity, reproducibility and non expensive and patient compliant outcomes makes it a valid option to achieve union in nonunion.

Phenotypic identification of periodontal Prevotella intermedia/nigrescens group isolates validated by MALDI-TOF mass spectrometry

The accuracy of a phenotypic scheme to recognize periodontal Prevotella intermedia/nigrescens group clinical isolates on primary isolation culture plates was assessed with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). A total of 84 fresh subgingival isolates from 23 chronic periodontitis patients were presumptively recognized on anaerobically-incubated enriched Brucella blood agar primary isolation plates as P. intermedia/nigrescens based on their dark-pigmented colony morphology, brick-red autofluorescence under long-wave ultraviolet light, and a negative fluorescence test for lactose production. The presumptive P. intermedia/nigrescens clinical isolates were subjected to MALDI-TOF MS analysis using Bruker MALDI Biotyper analytic software containing mass spectra for P. intermedia and Prevotella nigrescens in its reference library of bacterial protein profiles. Using a ≥1.7 log score agreement threshold, 60 (71.4%) of the presumptive P. intermedia/nigrescens clinical isolates were confirmed as either P. intermedia (25 isolates) or P. nigrescens (35 isolates). All isolates with a <1.7 log score were also identified as P. intermedia or P. nigrescens from the top choice designated on the MALDI Biotyper most likely species identification list. These MALDI-TOF MS findings document the ability of the phenotypic scheme to correctly recognize most periodontal P. intermedia/nigrescens group clinical isolates on primary isolation culture plates.

NSTX-U In-Vessel Control Coils’ Design Concept

A successful conceptual design was completed to develop in-vessel control coils [non-axisymmetric control coils (NCCs)]. The NCCs are a series of saddle coils that are intended to satisfy a number of physics criteria including magnetic breaking, error field control, fast resistive wall mode (RWM) control, and edge-localized-mode stabilization. Customized mineral-insulated cable (MIC) was selected for the conductor material. The MIC was made from oxygen-free copper conductor, high purity magnesium oxide powder insulation, and 304 stainless steel sleeve cover. Sample MIC was purchased from an outside supplier, and various tests were conducted for design and performance verification including high-voltage testing, which necessitated the development of special test terminations. A concept design was also developed for terminating the MIC ends using the nonconductive and vacuum-sealed technique. Two alternative designs were proposed for joints inside the vacuum vessel (VV). The NCCs are designed to be mounted in front of the primary passive plates and underneath the plasma-facing component (PFC) tiles. The passive plates will be modified to accommodate the coils. A new PFC tile design concept was developed using high-Z materials. New designs for the penetrations through the VV wall were developed. One port per coil was planned. A new power patch panel will be required to provide the ability for various combinations of connections between the NCC, the existing RWM coils, and the existing switching power amplifier power suppliers.

VHF suspended plate transmitter antenna design for DVB‐T and DAB‐T

AbstractThis paper presents the design of stacked suspended plate transmitter antenna for digital video and audio broadcasting. Contrary to conventional dipole structures, we have designed the antenna in VHF band (174–254 MHz) with two plates for wideband matching and design flexibility. Radiating primary plate has been excited by novel wideband modified inverted L‐type probe. Parasitic secondary plate, and vertical wall between primary plate, and ground plane have been used for further matching and beamwidth adjustment. A bandwidth of 42% and gain of 8.5 dBi is obtained at center frequency. Together with equivalent lumped element circuit model of designed antenna and experimental results for S11, gain, and radiation pattern are presented. To the best of authors knowledge this is the first stacked suspended plate antenna achieving a record bandwidth of 42% in VHF band.

Non-collinear interaction of guided elastic waves in an isotropic plate

The nonlinear wave propagation in a homogeneous and isotropic elastic plate is analyzed theoretically to investigate the non-collinear interaction of plate wave modes. In the presence of two primary plate waves (Rayleigh-Lamb or shear horizontal modes) propagating in arbitrary directions, an explicit expression for the modal amplitude of nonlinearly generated wave fields with the sum or difference frequency of the primary modes is derived by using the perturbation analysis. The modal amplitude is shown to grow in proportion with the propagation distance when the resonance condition is satisfied, i.e., when the wavevector of secondary wave coincides with the sum or difference of those of primary modes. Furthermore, the non-collinear interaction of two symmetric or two antisymmetric modes is shown to produce the secondary wave fields consisting only of the symmetric modes, while a pair of symmetric and antisymmetric primary modes is shown to produce only the antisymmetric modes. The influence of the intersection angle, the primary frequencies, and the mode combinations on the modal amplitude of secondary wave is examined for a low-frequency range where the lowest-order symmetric and antisymmetric Rayleigh-Lamb waves and the lowest-order symmetric shear horizontal wave are the only propagating modes.

A new species of the remarkable brittle star genus Astrophiura (Echinodermata: Ophiuroidea) from the western Atlantic Ocean

Astrophiura caroleae, new species, is described from off Curacao in the southern Caribbean, and from the western Gulf of Mexico, in depths of 244 to 434 meters. This new species, the first in the genus Astrophiura to be described from the Atlantic Ocean, has a distinctive combination of characters, including regularly arranged primary plates, large radial shields whose radial edges are in contact for their entire visible length, and prominent tubercles on central and radial plates. The mottled reddish coloration of the dorsal surface of this species usually contrasts with the color of the substratum, rendering it readily visible in situ, despite its disc diameter of less than 10 mm. Like its congeners, A. caroleae is gonochoric, the gonads of females containing conspicuous masses of bright orange eggs that are approximately 165 µm in diameter. DNA Barcoding data are provided for this new species, these are the first for Astrophiura.

Impact of brass contents on thermal, friction and wear properties of brake linings composites

Automotive brake lining materials are composite materials of very complex formulation, highly heterogeneous. They help to carry out the desired combination of braking performance properties. Obviously, it requires that the friction material exhibits good complementarities and adequate combination of physico-chemical, thermal properties that act synergistically to provide the braking performance which should be adjusted by the addition of metallic fillers. The aim of this work is to study the role of one of the copper alloy particles, namely brass, on friction and wear. For this purpose, the experimental approach is based on the development of a simplified formulation. Three derived composites were developed in the laboratory by the addition 1.5 wt.%, 3 wt.% and 4.5 wt.% of brass. It is shown that addition of copper alloy particles increased thermal properties. Wear test results show that brass contributes to friction and wear mechanisms from a quantity introduced in the formulation equal to 4.5 wt.%. In fact, given its large size, it acts as primary plates serving as supports for the formation and expansion of plates necessary to enhance the stability of friction coefficient. Conversely, when adding an amount less than 4.5%, brass particles are generally all removed from the matrix implying a higher source flow of third-body wear.

Rupture Along 400 km of the Bering Fracture Zone in the Komandorsky Islands Earthquake (MW 7.8) of 17 July 2017

AbstractThe 17 July 2017 Komandorsky Islands MW 7.8 earthquake involved arc‐parallel right‐lateral patchy strike‐slip faulting along ~400 km of the Bering Fracture Zone (BFZ) in the westernmost Aleutian Islands back arc. The large size of the earthquake indicates that the BFZ serves regionally as the primary plate boundary extending from the Near Islands to Kamchatka, with the fore‐arc Komandorsky Sliver translating rapidly parallel to the Aleutian Trench. The slip distribution is determined by analysis of seismic, tsunami, and geodetic observations. Fault displacements of 4 to 8.5 m, mostly in the upper 15 km, but with localized extension to 20 to 30 km depth along a ~100 km long segment of the BFZ, are comparable to the possible slip deficit since the last major earthquakes in this region in 1849 and 1858, given an estimated 5.1 cm/yr rate between the Komandorsky Sliver and the Bering Plate.

Friction stir welding of titanium alloys: A review

The candidacy of ninth earth abundant material, titanium is supreme when it comes to the higher strength to weight ratio, and higher corrosive resistance. Next generation of jet engines for aerospace industry clearly depends on the manufacturability and improved ability of titanium alloys that can withstand the high temperatures. However, the primary sheets, plates, billets, ingots, or rods are of limited sizes that need to be either machined or welded in order to produce a desired structure with optimal the buy-to-fly ratio. This article primarily summarizes the research in the field of joining of titanium sheets with a direct focus on friction stir welding (FSW). The industrial requirements, whether to weld similar or dissimilar titanium alloys, or of different thicknesses, or even with composites, are often challenged by the selection of the tool, position of the alloying sheets, cooling of the weld nugget, material composition, complex material flow in the wake of the rotating, and traversing tool etc. This article provides a review of FSW of similar and dissimilar titanium alloys focusing on surface, and subsurface properties, such as microstructural, and mechanical properties, texture evolution, current challenges summarizing a possible remedy, encompassing the recent development and research in the field.

Runx2 mediated Induction of Novel Targets ST2 and Runx3 Leads to Cooperative Regulation of Hypertrophic Differentiation in ATDC5 Chondrocytes

Knowledge concerning expression and function of Suppression of Tumorigenicity 2 (ST2) in chondrocytes is at present, limited. Analysis of murine growth plates and ATDC5 chondrocytes indicated peak expression of the ST2 transmembrane receptor (ST2L) and soluble (sST2) isoforms during the hypertrophic differentiation concomitant with the expression of the hypertrophic markers Collagen X (Col X), Runx2 and MMP-13. Gain- and loss-of-function experiments in ATDC5 and primary human growth plate chondrocytes (PHCs), confirmed regulation of ST2 by the key transcription factor Runx2, indicating ST2 to be a novel Runx2 target. ST2 knock-out mice (ST2−/−) exhibited noticeable hypertrophic zone (HZ) reduction in murine growth plates, accompanied by lower expression of Col X and Osteocalcin (OSC) compared to wild-type (WT) mice. Likewise, ST2 knockdown resulted in decreased Col X expression and downregulation of OSC and Vascular Endothelial Growth Factor (VEGF) in ATDC5 cells. The ST2 suppression was also associated with upregulation of the proliferative stage markers Sox9 and Collagen II (Col II), indicating ST2 to be a new regulator of ATDC5 chondrocyte differentiation. Runx3 was, furthermore, identified as a novel Runx2 target in chondrocytes. This study suggests that Runx2 mediates ST2 and Runx3 induction to cooperatively regulate hypertrophic differentiation of ATDC5 chondrocytes.

Neotectonic Deformation in Central Eurasia: A Geodynamic Model Approach

AbstractCentral Eurasia hosts wide orogenic belts of collision between India and Arabia with Eurasia, with diffuse or localized deformation occurring up to hundreds of kilometers from the primary plate boundaries. Although numerous studies have investigated the neotectonic deformation in central Eurasia, most of them have focused on limited segments of the orogenic systems. Here we explore the neotectonic deformation of all of central Eurasia, including both collision zones and the links between them. We use a thin‐spherical sheet approach in which lithosphere strength is calculated from lithosphere structure and its thermal regime. We investigate the contributions of variations in lithospheric structure, rheology, boundary conditions, and fault friction coefficients on the predicted velocity and stress fields. Results (deformation pattern, surface velocities, tectonic stresses, and slip rates on faults) are constrained by independent observations of tectonic regime, GPS, and stress data. Our model predictions reproduce the counterclockwise rotation of Arabia and Iran, the westward escape of Anatolia, and the eastward extrusion of the northern Tibetan Plateau. To simulate the observed extensional faults in the Tibetan Plateau, a weaker lithosphere is required, provided by a change in the rheological parameters. The southward movement of the SE Tibetan Plateau can be explained by the combined effects of the Sumatra trench retreat, a thinner lithospheric mantle, and strik‐slip faults in the region. This study offers a comprehensive model for regions with little or no data coverage, like the Arabia‐India intercollision zone, where the surface velocity is northward showing no deflection related to Arabia and India indentations.

Comparison of union rates and functional outcomes for displaced mid-shaft clavicular fractures at Bhuj-Kutch: a prospective study

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Clavicle fracture usually treated conservatively. There is a rising tendency to treat displaced mid-shaft clavicular fractures with primary open reduction and plate fixation; whether such treatment outcome in enhanced patient outcomes is contentious. The aim of this study was to compare union rates and functional outcomes for displaced mid-shaft clavicular fractures that were treated with either primary open reduction and plate fixation or nonoperative treatment.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; Present study was performed at department of orthopedics, Gujarat Adani institute of medical science, Bhuj, Kutch, Gujarat. Ethical clearance was taken from the institutional ethics board and informed consent was obtained from all the participants. In this study, patients who had an acute displaced mid-shaft clavicular fracture were randomized to receive either primary open reduction and plate fixation or nonoperative treatment. Functional evaluation was conducted at 3 months, 6 months, and 1-year with the use of the constant scores. Union was evaluated clinically and radiographically. Complications were recorded and compared.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; The rate of nonunion was reduced significantly after open reduction and plate fixation as compared with nonoperative treatment. Constant scores were significantly improved after open reduction and plate fixation than after nonoperative treatment; 93.7 versus 85.5. A major complication was found in 34.9% of patients in the conventional group while they were absent in operative group.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; Open reduction and plate fixation decrease the rate of nonunion after acute displaced mid-shaft clavicular fracture compared with nonoperative treatment and is connected with improved functional outcomes. Open reduction and plate fixation using precontoured locking plate have little implant-related complications.&lt;/p&gt;

The Microevolution and Epidemiology of Staphylococcus aureus Colonization during Atopic Eczema Disease Flare

Staphylococcus aureus is an opportunistic pathogen and variable component of the human microbiota. A characteristic of atopic eczema (AE) is colonization by S. aureus, with exacerbations associated with an increased bacterial burden of the organism. Despite this, the origins and genetic diversity of S. aureus colonizing individual patients during AE disease flares is poorly understood. To examine the microevolution of S. aureus colonization, we deep sequenced S. aureus populations from nine children with moderate to severe AE and 18 non-atopic children asymptomatically carrying S. aureus nasally. Colonization by clonal S. aureus populations was observed in both AE patients and control participants, with all but one of the individuals carrying colonies belonging to a single sequence type. Phylogenetic analysis showed that disease flares were associated with the clonal expansion of the S. aureus population, occurring over a period of weeks to months. There was a significant difference in the genetic backgrounds of S. aureus colonizing AE cases versus controls (Fisher exact test, P = 0.03). Examination of intra-host genetic heterogeneity of the colonizing S. aureus populations identified evidence of within-host selection in the AE patients, with AE variants being potentially selectively advantageous for intracellular persistence and treatment resistance.

Sea urchin growth dynamics at microstructural length scale revealed by Mn-labeling and cathodoluminescence imaging

BackgroundFluorochrome staining is among the most widely used techniques to study growth dynamics of echinoderms. However, it fails to detect fine-scale increments because produced marks are commonly diffusely distributed within the skeleton. In this paper we investigated the potential of trace element (manganese) labeling and subsequent cathodoluminescence (CL) imaging in fine-scale growth studies of echinoderms.ResultsThree species of sea urchins (Paracentrotus lividus, Echinometra sp. and Prionocidaris baculosa) were incubated for different periods of time in seawater enriched in different Mn2+ concentrations (1 mg/L; 3 mg/L; 61.6 mg/L). Labeling with low Mn2+ concentrations (at 1 mg/L and 3 mg/L) had no effect on behavior, growth and survival of sea urchins in contrast to the high Mn2+ dosage (at 61.6 mg/L) that resulted in lack of skeleton growth. Under CL, manganese produced clearly visible luminescent growth fronts in these specimens (observed in sectioned skeletal parts), which allowed for a determination of the average extension rates and provided direct insights into the morphogenesis of different types of ossicles. The three species tend to follow the same patterns of growth. Spine growth starts with the formation of microspines which are simultaneously becoming reinforced by addition of thickening layers. Spine septa develop via deposition of porous stereom that is rapidly (within less than 2 days) filled by secondary calcite. Development of the inner cortex in cidaroids begins with the formation of microspines which grow at ~3.5 μm/day. Later on, deposition of the outer polycrystalline cortex with spinules and protuberances proceeds at ~12 μm/day. The growth of tooth can be rapid (up to ~1.8 mm/day) and starts with the formation of primary plates (pp) in plumula. Later on, during the further growth of pp in aboral and lateral directions, secondary extensions develop inside (in chronological order: lamellae, needles, secondary plate, prisms and carinar processes), which are increasingly being solidified towards the incisal end. Interradial growth in the ambital interambulacral test plates exceeds meridional growth and inner thickening.ConclusionsMn2+ labeling coupled with CL imaging is a promising, low-cost and easily applicable method to study growth dynamics of echinoderms at the micro-length scale. The method allowed us to evaluate and refine models of echinoid skeleton morphogenesis.

Martensite Transformation Intergrain and Intragrain Autocatalysis in Fe-Ni alloys

This work presents a consolidated view of the autocatalysis, thermal and entropic effects in martensitic transformation of polycrystalline Fe-31wt%Ni-0.02wt%C, which has been a standard material for the investigation of fundamental aspects of the martensite transformation. The present work is based on the description of classical microstructure descriptors of the transformation and on generally accepted concepts regarding the martensitic transformation in iron base alloys. Present work agrees with the view that the autocatalysis is a means by which the martensite transformation promotes further nucleation and growth. Autocatalysis induces the nucleation and growth of secondary plates in addition to the relatively small number of primary nucleation sites and their corresponding primary plates. We demonstrate that autocatalysis can be factored out into intragrain and intergrain components. The analysis of these factors establishes that intragrain autocatalysis is athermal but intergrain autocatalysis possess an Arrhenius temperature dependence. The reasons for such a behavior are discussed in detail.