Pit Size Research Articles

Structure And Corrosion of Quasicrystalline Cast Al–Co–Ni and Al–Fe–Ni Alloys in Aqueous NaCl Solution

In this work the structure and corrosion behavior of quasicrystalline cast Al69Co21Ni10 and Al72Fe15Ni13 alloys in 5-% sodium chloride solution (рН 6.9–7.1) were investigated. The alloys were cooled at 5 К/s. The structure of the samples was studied by methods of quantitative metallography, X-ray analysis, and scanning electron microscopy. Corrosion properties were determined by potentiodynamic method. Stationary potential values were measured by means of long-term registration of (Е,τ)–curves using ПІ–50–1 potentiostat and ПР–8 programmer with three-electrode electrolytic cell. A platinum electrode served as counter electrode and silver chloride – as reference electrode. The made investigations confirm the formation of stable quasicrystalline decagonal D-phase in the structure of Al69Co21Ni10 and Al72Fe15Ni13 alloys. In Al69Co21Ni10 alloy, at room temperature D-phase coexists with crystalline Al9(Co,Ni)2 phase, and in Al72Fe15Ni13 alloy – with Al5FeNi phase. Comparison of Vickers hardness of these phases exhibits the following sequence: H(D-AlCoNi)>H(D-AlFeNi)>H(Al5FeNi)>H(Al9(Co,Ni)2). In 5-% sodium chloride solution, the investigated alloys corrode under electrochemical mechanisms with oxygen depolarization. Compared with Al72Fe15Ni13 alloy, Al69Co21Ni10 alloy has more negative value of stationary potential (–0,40 V and –0,48 V, respectively), and its electrochemical passivity region extends due to the inhibition of anodic processes. For both alloys, transition to passive state in the saline solution is observed. A corrosion current density, calculated from (E,lgi)-curve, for Al69Co21Ni10 alloy amounts to 0.12 mА/сm2 and for Al72Fe15Ni13 alloy – to 0.14 mА/сm2. After immersion in the saline solution for 8 days, pits are revealed on the surface of the alloys in areas, mainly where the phase boundaries and flaws are located. The number and size of pits are smaller on the surface of Al69Co21Ni10 alloy as compared with those on the surface of Al72Fe15Ni13 alloy. The lower corrosion resistance of Al72Fe15Ni13 alloy may be explained by the presence of iron-containing phases in its structure. Based on obtained results, the Al69Co21Ni10 alloy has been recommended as coating material for rocket-and-space equipment working in marine climate.

Serial Changes in Image Findings of Herniation Pits from the First Appearance.

BackgroudHerniation pits (HPs) have been considered to be an incidental finding, but recently femoroacetabular impingement (FAI) has been proposed as a possible cause of their formation. The findings on bone scans of HPs are variable in the literature: some showed increased uptake; the majority did not. We hypothesized that serial changes in image findings of HPs would explain the reason for the variable bone scan findings.MethodsFour patients (5 hips) were followed up for more than 7 years. All patients were women and regularly underwent bone scintigraphy after the diagnosis of breast cancer. Small lesions with increased uptake were first detected on bone scintigraphy at the age of 44 to 64 years. In all cases, the lesions were confirmed by magnetic resonance imaging and follow-up bone scintigrams were taken regularly. Four lesions were also evaluated by computed tomography. Changes in the size of the pits and the intensity of the increased uptake on bone scintigraphy were evaluated.ResultsOn the bone scintigrams, the lesions with increased uptake were detected in the femoral neck at 5–20 months after previous negative bone scintigraphy. There had been no events or symptoms associated with the newly detected increased uptake. On follow-up scans, the intensity of the uptake decreased gradually and the areas of increased uptake disappeared completely at 14–50 months after their first appearance. In 3 cases (2 patients), the pit size increased during follow-up.ConclusionsThe areas of increased uptake on bone scintigraphy gradually disappeared in all cases and the increase in pit size was frequent. There was no case in which signs or symptoms suggestive of FAI were noticed.

Bung: A traditional practice of potato cultivation in eastern hills of Nepal

Eastern hill region is one of the high potato producing areas of potato in Nepal. There are many traditional potato production systems existing in the region. Among them, 'Bung' and 'Lhose' are very popular systems. There are some under-proven views of naming to this unique cultivation practice. Field observations, key informants' interview, and group discussion were carried out at three sites of Okhaldhunga and Solukhumbu districts in July 2019 to explore the basic information on the bung system. The results of this investigation revealed that the century-old practice utilized marginal sloppy lands of mountains for cultivation of potatoes. Farmers left land fallow for 4-5 years to grow weeds and herbs. Thereafter, they slashed them with a thin layer of soil, stacked them over winter, burned and mixed with the soil making a raised pit. They planted 15-25 potato seed tubers into these pits depending upon the pit size. No additional fertilizer is added to these pits. No intercultural operations are carried out until harvesting. It was explained that the yield of potato from the bung was significantly higher 15-20 kg) than that of general local practice called lhose system (5-7 kg) from the area equivalent to Bung . Some interventions such as high yielding varieties, easy-to-handle equipment for bung preparation and introduction of fast-growing non-hazardous weeds, etc. were the demands of the farmers to increase profit from the bung system.

Simulation and experiments of abrasive assisted electrochemical jet machining of SiC reinforced aluminum matrix composites

Silicon carbide reinforced aluminum matrix composites (SiCp/Al) exhibit excellent properties and performance in fields of aerospace, electronic packaging, precision instrumentation and automotive industry. The SiCp/Al composites are hard-to-machine materials due to different physical properties between reinforcement material and matrix material. This study investigated the removal mechanism of the reinforcement in abrasive assisted electrochemical jet machining (AECJM) of SiCp/Al composites through simulation and experiments. The results show that the lifetime of the bonding interface between SiC and matrix significantly decreases with lowering of the bonding area. For a given bonding area, the lifetime of that is proportional to the SiC size. Therefore, the material removal rate is markedly influenced by the SiC particle size. The SiC reinforcement can be extracted out when the bonding area drops off to a low level. This results in many micro pits left at the machined surface. The roughness of the surface is highly related to the number and size of these micro pits. Larger size of or higher volume fraction of the reinforcement will result in rougher machined surfaces.

Effects of characteristic parameters of corrosion pits on the fatigue life of the steel wires

To study the influence of corrosion pits on fatigue life of high-strength steel wire, 69 cable steel wires with different characteristic parameters of pits were obtained by manual prefabrication. The effects of pit depth, width, location and stress amplitude on the fatigue life of steel wires were investigated through the fatigue test. Then, the prediction model of fatigue life of steel wire with corrosion pits was established. Finally, 236 finite element models (FEM) of steel wire with corrosion pits were established by the software ANSYS and nCode designLife, and the SN curves of steel wires with different sizes of pit and stress ratios were also analyzed. The results showed that the fatigue life of steel wire decreased significantly when the depth of pit was in the range of 0.2–0.6 mm, with a maximum reduction of 99.25%. The slight change of stress amplitude would result in the fatigue life by several times or even ten times. The superposition effect of pits would slightly increase the fatigue life of steel wire. In addition, when the stress ratio increased from −1 to 0.44, the SN curve of steel wire with 0.16 of depth-width ratio of pits would move down more than twice than that of steel wire with 0.75 of depth-width ratio of pits. For finite life design, the fatigue life of steel wire changed from high cycle fatigue to low cycle fatigue with the increase of depth-width ratio of pits. When the depth-width ratio was >1, the corresponding stress amplitude was not affected by the pit sizes under the same fatigue life. The effect of stress ratio on wide-shallow pits was greater than that on deep-narrow pits.

Influence of temperature on corrosion resistance of austenitic stainless steel in cl− containing solutions

Abstract Temperature is considered a complicated external factor of the susceptibility of stainless steels to the pitting. This paper deals with the corrosion behaviour of AISI 316Ti stainless steel in temperature range 22 - 80°C in aggressive chloride environments (3 and 5% FeCl3 solutions). The corrosion resistance of tested steel is evaluated on the base of results of exposure immersion tests and cyclic potentiodynamic tests. According to the obtained results the resistance of AISI 316Ti to the pitting is markedly affected by temperature changes in the range 22 – 80°C. Intensity of corrosion attack increases with the rise of Cl− concentration. Gentle changes of temperature and Cl− concentration cause significant differences in character of local damage. The appearance of pitted surfaces changes with the rise of the temperature (a density of pitting increases, a size of pits decreases). The strongest change in appearance is observed between 40 and 50ºC.

Microstructure and corrosion evolution of additively manufactured aluminium alloy AA7075 as a function of ageing

Additively manufactured high strength aluminium (Al) alloy AA7075 was prepared using selective laser melting (SLM). High strength Al-alloys prepared by SLM have not been widely studied to date. The evolution of microstructure and hardness, with the attendant corrosion, were investigated. Additively manufactured AA7075 was investigated both in the “as-produced” condition and as a function of artificial ageing. The microstructure of specimens prepared was studied using electron microscopy. Production of AA7075 by SLM generated a unique microstructure, which was altered by solutionising and further altered by artificial ageing—resulting in microstructures distinctive to that of wrought AA7075-T6. The electrochemical response of additively manufactured AA7075 was dependent on processing history, and unique to wrought AA7075-T6, whereby dissolution rates were generally lower for additively manufactured AA7075. Furthermore, immersion exposure testing followed by microscopy, indicated different corrosion morphology for additively manufactured AA7075, whereby resultant pit size was notably smaller, in contrast to wrought AA7075-T6.

Metastable pitting behaviour of austenite stainless steel under compressive residual stress

AbstractMetastable pitting behaviour of austenite stainless steel after compressive deformation in an acidic NaCl solution was investigated. The results show that the pit initiation rate increases while both metastable pit lifetime and growth rate decrease after compressive deformation. Meanwhile, the ratio of the surface oxide fraction of Cr to Fe increases whereas the average size of stable pits is smaller and shallow disk‐shaped under compressive residual stress. The results reveal that with the aid of enrichment of Cr oxides and compressive residual stress, which helps break the remnants of the undermined passive film, pit repassivation can be accelerated.

Effect of unevenly-distributed V pits on the optical and electrical characteristics of green micro-light emitting diode

In this study, we investigated the effect of different-size V pits on the opto-electrical performance of different-size InGaN-based green (520 nm) light-emitting diodes (LEDs). The size of V pits varied from 57 to 250 nm. Two different-size LEDs (10 and 300 µm) were fabricated with flip-chip structures. It was shown that at 4 A cm−2, the forward voltages of 300 µm-size and 10 µm-size LEDs were in the range of 2.32–2.82 V and 2.23–2.53 V, respectively. Compared with the LEDs with small V pits, the LEDs with large V pits produced higher output power at the high current region (>50 A cm−2), but lower output power at the low current region (<20 A cm−2). The 300 µm-size LEDs displayed maximum external quantum efficiency (EQE) at 2 A cm−2, whereas the 10 µm-size LEDs exhibited peak EQE at current densities ⩾13 A cm−2. For all samples, the electroluminescence (EL) wavelengths were blue shifted with increasing current density. Unlike the 300 µm-size LEDs, the 10 µm-size LEDs exhibited a large deviation in the light output, EQE, and EL wavelength. The 10 µm-size LEDs revealed larger S than the 300 µm-size LEDs. The backscattered electron (BSE) and monochromatic cathodoluminescence (CL) results showed that for all samples, V pits were unevenly distributed across the whole wafer. Based on the CL and BSE results, the effect of different V pit sizes on the performance of green micro-LEDs at the low current region is described and discussed.

New insights into wood anatomy and function relationships: How Eucalyptus challenges what we already know

Multispecies surveys have shown that there is a weak but significant trade-off between xylem efficiency and safety in woody species, with no species maximizing both attributes at the same time. Relationships between xylem structure and function are studied mostly at the interspecific level, with few studies considering the relationships at the intraspecific level, particularly in angiosperms. Studies have shown that relationships between xylem anatomy or wood density and vulnerability to cavitation (which determines xylem safety) observed in multi-species surveys may be different to those observed within a species. This raises the question about the value of multispecies studies to shed light over what is adaptive within a given species, the organization level at which natural and human selection operates. To contribute to this debate, we studied xylem structure and function in four Eucalyptus species, and made focus within one of them, E. globulus, to determine if patterns observed at the interspecific level are also held within a species. Eucalyptus species have a xylem composed by solitary vessels surrounded and connected to imperforate tracheary cells and parenchyma, a particular anatomy poorly known in terms of its function. Correlation analyses revealed that the trends observed between vessel size (mean and distribution) and vulnerability to cavitation are similar at the interspecific and intraspecific levels. Moreover, no trade-off has been observed between xylem efficiency (maximum hydraulic conductivity) and safety (water potential at 12% and 50% of hydraulic conductivity loss), but the opposite trend: individuals with mean larger vessels presented lower vulnerability to cavitation. Cells around vessels (parenchyma, vasicentric tracheids, fibertracheids) could be involved in this phenomenon since they correlate both with maximum hydraulic conductivity (positively) and vulnerability to cavitation (negatively) at the interspecific level. In addition, large xylem vessels presented smaller pits than small xylem vessels. This suggests that pit size is involved in the lack of trade-off between xylem safety and efficiency. Finally, vulnerability to cavitation was correlated with branch and stem wood density of the same tree, but correlations had opposite sign depending on the plant organ. These results provide new insights into the relationships between wood structure and function of angiosperm species.

Arthropods Captured Using an Adhesive Trap in a Pecan Plantation in the South of Brazil

This study aimed to evaluate the arthropod fauna associated with pecan trees [Carya illinoinensis (Wangenh.) K. Koch] (Juglandaceae) in the south of Brazil. The experiment was conducted in a C. illinoinensis plantation of approximately 1.2 hectares, divided into 7 m × 7 m areas that were subjected to different soil preparations and pit sizes, in Santa Maria, RS, Brazil. A randomized block design with five blocks and four treatments was used: planting in small pits of 20 cm × 60 cm (Sp); using a subsoiler with a leveling grader/shank and small pits (Ssp); using a rotary tiller and small pits (Tsp); and planting in large pits of 40 cm × 60 cm (Lp). Eighteen biweekly samplings were carried out from March 2014 to May 2015 using yellow adhesive traps in all treatment areas. No statistically significant difference in abundance or arthropod richness was observed. The population peak of Monellia caryella (Fitch) (Aphididae) occurred in April 2014. After the population growth of M. caryella, an increase in Coccinellidae in the traps was observed. It can be concluded that the different soil preparations and pit sizes proposed for pecan planting do not affect the diversity of the arthropods collected using yellow adhesive traps.

Role of CaMKK2 in Osteoclast Development and Function

Background and Hypothesis: In bone remodeling there are two opposing forces, osteoclast resorption and osteoblast synthesis of bone. When there is an imbalance, osteoporosis is likely found. We look to determine the role that Ca2+/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) has on osteoclast development and attachment. Previous studies show that Camkk2-/- mice have fewer mature osteoclasts that display poor attachment to the bone. These results suggest that there is a defect in facilitating osteoclast differentiation, or a defect in the attachment itself. Thus, we hypothesize that CaMKK2 plays an integral role in the development and function of the osteoclast cytoskeleton.&#x0D; Experimental Design or Project Methods: We plated different concentrations of bone marrow cells isolated from male and female, wildtype and Camkk2-/- mice to investigate size and number of mature osteoclasts present. We examined the size of the resorption pits made by these osteoclasts, when plated on calcium phosphate-coated surfaces. We analyzed the RNA and protein and stained the cells immunohistochemically for proteins associated with cell attachment.&#x0D; Results: There were greater numbers of mature osteoclasts in the Camkk2-/- males at each density than the wildtype males. The female mice followed the same trend, but with fewer osteoclasts overall.&#x0D; The average area per resorbed pit was two-times larger in the WT males than the Camkk2-/- males. But, for the females the opposite trend is shown, the pits from the Camkk2-/- females were twice as large as those formed from the wildtype females.&#x0D; To gauge efficiency, we calculated the average area resorbed per osteoclast. For the males, significantly greater efficiency from the wildtype osteoclasts was found than the Camkk2-/- osteoclasts. For the females, there was no difference in efficiency at the lower plating densities, but the osteoclasts from the Camkk2-/- females had greater efficiency at the greater densities.&#x0D; Remaining results are to be finalized. &#x0D; Conclusion and Potential Impact: With the decrease in efficiency of Camkk2-/- mice osteoclasts, we believe that CaMKK2 is necessary for the attachment of OCs. CaMKK2 could be a target to slow the pathologic breakdown of bone.

Funerary customs of Golasecca Culture

Both M. Primas in 1970 and the Author in 1988 argued that within the Golasecca culture three cultural facies were recognizable: Como, Golasecca, Sopraceneri including Mesolcina. On the basis of the available data then it could be said that in the first two facies the exclusive funerary rite was cremation, while to the north of the Monte Ceneri gradually passed from cremation to biritualism and finally to inhumation as an exclusive funeral rite. Recently the thesis was presented that in the Golasecca facies also inhumation tombs were present. According to Gambari, two pit tombs of the necropolis of Pombia, the t. 12/1995 and the t. 15/1995, would be interpreted as childhood or adolescence inhumation graves. In the complete absence of skeletal remains, the hypothesis was formulated solely on the basis of the pit size, which was not exceptional. According to Grassi and Mangani four pit tombs of the necropolis of Monsorino di Golasecca would always be inhumations exclusively on the basis of the pit size. The Author rejects these interpretations as unfounded. First of all, in the absence of skeletal remains due to the strong acidity of the soil, two hypotheses can be taken into consideration: the inhumation or the rite of spreading the burnt bones on the bottom of the tomb. The analysis of the grave goods indicates as likely the second hypothesis. For example in the tomb 12/1995 there is a fragment of a broken and bent pin. De-functionalization in accordance with ritual norms is characteristic of cremation tombs. In the necropolis of Pombia two tombs, the 4/1995 and the 7/1995, have a size comparable to those considered to be inhumations, but burnt bones were discovered in them, thus confirming the ritual of spreading the ashes on the bottom of the tomb. In the tomb 39 of Monsorino a beaker with a globular body and distinct neck has the ribbon handle removed with a clean cut both to the upper and lower attachment, according to a ritual norm typical of the Golasecca culture when a pot is used as a container for the burnt bones, also in the same grave the metal objects have been discovered towards one end of the pit, but if it were an inhumation tomb the bronze belt-plate should be in the center of the pit. Grassi, Mangani and Voltolini argue that the grave of the Tripod from Sesto Calende-Bellaria would have been an inhumation burial, relying on the position of the objects, moreover they believe that the tomb would have had a bottom entirely covered with wooden planks and also a covering of wooden planks and it would never have been subject to violation with removal of the slab cover and part of the grave-goods. The author presents the excavation data, some of which are still unpublished, which clearly demonstrate the violation of the tomb and the unreliability of the reconstruction proposed by Grassi, Mangani and Voltolini. Since no rest of the skeleton has been preserved, one must think of its complete dissolution due to the nature of the soil, too acidic, but this fact is denied by the preservation of animal bones in one of the cups. Furthermore, in the NE corner of the tomb the body of a small leech fibula was found, devoid of spring, and catch-plate, all deformed by thermal effect, evidently coming from the funerary pyre. The arrangement of the materials is incompatible with the hypothesis of an inhumation, in particular an iron spit was found mixed with the chains of the long pendant / breastplate. Grassi, Mangani and Voltolini believe that the incontrovertible proof of the existence of inhumation burials in the facies of Golasecca and Como are two tombs from the small necropolis of Urago d’Oglio, dated to the second half of the fifth century and attributed to the Golasecca culture. This thesis is the result of a series of macroscopic typological classification, dating and cultural background mistakes. In fact, four cremation graves can be dated to the end of the sixth century, while two inhumations date back to the La Tene B (fourth century BC) and must be attributed to the Cisalpine Gauls.

Thermal annealing induced cave in and formation of nanoscale pits in Ag–TiO2 plasmonic nanocomposite thin film

Ag–TiO2 nanocomposite thin films on silica glass were prepared through thermal evaporation in combination with RF magnetron sputtering. Thermal annealing induced changes in the optical, morphological and structural properties of Ag–TiO2 nanocomposites were examined using optical absorption, photoluminescence spectroscopy, Raman spectroscopy, FESEM, AFM and XRD. FESEM and AFM studies revealed cave in of the Ag–TiO2 thin film at various places leading to the formation nanoscale pits upon thermal annealing at 600 °C. The computed average size of pits was found to be 54 nm. Raman studies indicated 600 °C annealing induced transformation of anatase phase of TiO2 into anatase/rutile mixed phase TiO2. Optical absorption spectra showed systematic changes due to the effects of mixed phase formation and variation in the plasmonic behavior upon annealing. PL results of the as deposited Ag–TiO2 thin film showed peaks at 377, 402, 432 and 486 nm. PL studies of Ag–TiO2 nanocomposites treated at different annealing temperatures revealed changes in defect concentration in TiO2. The tentative mechanism for the creation of nanoscale pits in Ag–TiO2 thin film through thermal annealing was proposed.

Coupling Effects of pH and Dissolved Oxygen on the Corrosion Behavior and Mechanism of X80 Steel in Acidic Soil Simulated Solution.

In an acidic red soil environment, the corrosion mechanism of X80 steel may be closely related to the pH value and oxygen content, but it has not yet formed a systematic understanding. In this paper, the coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in an acidic soil simulated solution were further analyzed by electrochemical methods and three-dimensional video microscope. Results showed that the hydrogen reduction reaction was almost the only cathode process in the anoxic and low pH system, and small and dense pits were present on the electrode surface. pH value increased, the pits decreased, but the size of pits increased. In the oxygen-adequate system, oxygen-consuming (OC) corrosion preferentially occurred, and a protective corrosion product layer (including FeOOH, Fe3O4, etc.) might be formed accordingly, but the proportion of hydrogen evolution (HE) increased and the product layer had defects at a low pH environment. The specific corrosion mechanism of X80 steel in an acidic soil simulated solution is described in the relevant models.

Through-thickness inhomogeneity of precipitate distribution and pitting corrosion behavior of Al–Li alloy thick plate

Abstract The thorough-thickness inhomogeneity of precipitate distribution and pitting corrosion behavior of 95 mm-thick 2297 Al−Li alloy rolled plate was investigated using scanning electron microscopy, transmission electron microscopy and electrochemistry method. Precipitate distribution and pit size were statistically analyzed to obtain quantitative information and corresponding correlation. The population density and the size fraction of precipitate on different sections in the thick plate are ranked from high to low in the following order: quarter-section (QS) > surface section (SS) > mid-section (MS). After 300 min potentiostatic polarization, the number and the total volume of pits are ranked from high to low as QS>SS>MS, indicating a higher pitting susceptibility of the plate in QS with more precipitates. The through-thickness inhomogeneity of pitting corrosion in 2297 Al−Li alloy thick plate is mainly ascribed to inhomogeneous precipitate distribution.

Commensal Bacteria Regulate Gene Expression and Differentiation in Vertebrate Olfactory Systems Through Transcription Factor REST.

Sensory systems such as the olfactory system detect chemical stimuli and thereby determine the relationships between the animal and its surroundings. Olfaction is one of the most conserved and ancient sensory systems in vertebrates. The vertebrate olfactory epithelium is colonized by complex microbial communities, but microbial contribution to host olfactory gene expression remains unknown. In this study, we show that colonization of germ-free zebrafish and mice with microbiota leads to widespread transcriptional responses in olfactory organs as measured in bulk tissue transcriptomics and RT-qPCR. Germ-free zebrafish olfactory epithelium showed defects in pseudostratification; however, the size of the olfactory pit and the length of the cilia were not different from that of colonized zebrafish. One of the mechanisms by which microbiota control host transcriptional programs is by differential expression and activity of specific transcription factors (TFs). REST (RE1 silencing transcription factor, also called NRSF) is a zinc finger TF that binds to the conserved motif repressor element 1 found in the promoter regions of many neuronal genes with functions in neuronal development and differentiation. Colonized zebrafish and mice showed increased nasal expression of REST, and genes with reduced expression in colonized animals were strongly enriched in REST-binding motifs. Nasal commensal bacteria promoted in vitro differentiation of Odora cells by regulating the kinetics of REST expression. REST knockdown resulted in decreased Odora cell differentiation in vitro. Our results identify a conserved mechanism by which microbiota regulate vertebrate olfactory transcriptional programs and reveal a new role for REST in sensory organs.

Detection of Defects in Diamond by Etch‐Pit Formation

Correlation between the reverse current densityJRof diamond vertical Schottky barrier diodes (SBD) and the shape of the etch pits is investigated. Etch pits form throughout the whole epitaxial layer area with a density of 6.8 × 104–3.0 × 105 cm−2. Most etch pits are isolated‐type, with flat‐bottom or point‐bottom shape. A typical pit size is 3–5 μm in width and 1–3 μm in depth. Some etch pits aggregate linearly with a size of &gt;10 μm. The SBDs show largeJRwhen these etch pit clusters appear. The etch pit cluster density is &lt;103 cm−2.

Effect of Pre-Corrosion Pits on Residual Fatigue Life for 42CrMo Steel

The effect of pre-corrosion pits on residual fatigue life for the 42CrMo steel (American grade: AISI 4140) is investigated using the accelerated pre-corrosion specimen in the saline environment. Different pre-corroded times are used for the specimens, and fatigue tests with different loads are then carried out on specimens. The pre-corrosion fatigue life is studied, and the fatigue fracture surfaces are examined by a surface profiler and a scanning electron microscope (SEM) to identify the crack nucleation sites and to determine the size and geometry of corrosion pits. Moreover, the stress intensity factor varying with corrosion pits in different size parameters is analyzed based on finite element (FE) software ABAQUS to derive the regression formula of the stress intensity factor. Subsequently, by integrating the regression formula with the Paris formula, the residual fatigue life is predicted and compared with experimental results, and the relationship of the stress intensity factor, pit depth, and residual fatigue life are given under different corrosion degrees. The fatigue life predicted by the coupled formula agrees well with experiment results. It is observed from the SEM images that higher stress amplitude and longer pre-corroded time can significantly decrease the residual fatigue life of the steel. Additionally, the research work has brought about the discovery that the rate of crack extension accelerates when the crack length increases. The research in this paper also demonstrates that the corrosion pit size can be used as a damage index to assess the residual fatigue life.

Hydrogen gas protects against ovariectomy-induced osteoporosis by inhibiting NF-κB activation.

Osteoporosis is a prevalent condition among postmenopausal women, and lacks satisfactory therapeutic options. Hydrogen (H2) has been shown to be effective in alleviating many diseases. This study aimed to investigate the effects of H2 on inhibiting osteoclastogenesis and bone loss in ovariectomized mice. Osteoclast differentiation from Raw264.7 cells was induced with receptor activator NF-κB ligand (RANKL) with or without 60% H2. The number and resorption activity of osteocalsts were assessed by tartrate-resistant acid phosphatase staining and pit formation assay, respectively. The expression of osteoclast markers and NF-κB phosphorylation were detected by western blot. NF-κB nuclear translocation was assessed by immunofluorescence. NF-κB transcriptional activity was analyzed by luciferase assay. Bone loss in mice was induced by ovariectomy (OVX). OVX mice were given either regular air or 60% H2. Bone structure was analyzed by micro-computed tomography and hematoxylin and eosin staining. Cytokine levels were measured by enzyme-linked immunosorbent assay. The data were analyzed with one-way or two-way ANOVA followed by Bonferroni post hoc tests. H2 did not have any measurable effect on the proliferation of Raw264.7 cells. The number of osteoclasts and size of resorption pits of RANKL+H2-treated cells were 3 to 4 times less than RANKL treated cells. The expression of osteoclast marker genes of RANKL+H2-treated cells was 30% to 60% lower than RANKL-treated cells (P < 0.05). H2 markedly inhibited RANKL-induced activation, nuclear translocation, and transcriptional activity of NF-κB (P < 0.05, RANKL+H2 vs RANKL). The amount and density of trabecular bone and bone mineral density of ovariectomized mice were significantly less than sham-operated mice (P < 0.05 OVX vs sham). The amount of trabecular bone and bone mineral density of OVX mice that inhaled H2 were more than 40% higher, whereas the levels of serum proinflammatory cytokine interleukin 1β, IL-6, and tumor necrosis factor-α were more than 50% lower than those of OVX mice (P < 0.05). These results demonstrated that H2 could be an effective therapeutic agent of postmenopausal osteoporosis.