Local Scratch Research Articles

Effect of Cr and Ni on mechanical response and microstructural evolution of nanocrystalline ferrite: A molecular dynamics study

Microalloying plays a critical role in improving the mechanical properties of steel. To offer a better theoretical guide for experimental research at the atomic level, this paper investigated the synergistic mechanism of adding trace amounts of alloy Cr and Ni and the microstructure evolution of nanocrystalline ferrite during the mechanical response process. First-principles calculations were implemented to investigate electronic properties. Hybrid molecular dynamics and Monte Carlo simulations were employed to explore the deformation mechanism under uniaxial tension and scratching. Specifically, comprehensive differences between doped and pure nanocrystalline ferrites were explored regarding local stress-strain state, dislocation evolution, twin expansion, and grain boundary activity. The results show that Cr- and Ni-doped nanocrystalline ferrite has higher strength and better wear resistance. The potential mechanism is that the addition of Cr and Ni enhances the atomic bonding strength with Fe atoms, hinders the movement of dislocations caused by lattice distortion, and suppresses grain boundary slip and migration, thereby improving the resistance to plastic deformation and grain boundary stability. Theoretical calculations based on microstructure indicate that compared to solid solution strengthening, Ni-induced grain boundary strengthening plays a dominant role in improving yield strength. Under large deformation, the trend of mechanical response is reversed. The suppression of dislocation motion by Cr reduces the dislocation density and dislocation entanglement, resulting in flow stress and local scratch force being smaller than that of pure samples. However, the formation of more nanoscale twins and twin-dislocation interactions enhances strain-hardening ability during tensile. Finer nanostructured subgrains are formed under scratching. These results provide valuable insights into the understanding of the strengthening mechanism and plastic deformation mechanism of Cr-Ni system low alloy steel under dynamic loading.

Direct shear experiment on salt rock incorporating loading rate effect

To investigate the shear behavior of salt rock under different loading rates, direct shear testing was conducted on high-purity salt rock obtained from Pakistan using a YZW-100 apparatus. The experimental results of the shear stress, deformation, and failure characteristics of the salt rock showed that the loading rate is an essential factor influencing the shear strength parameters of the rock. When the shear loading rate was increased, the cohesion of the salt rock significantly increased; however, the internal friction angle slightly decreased, nearly remaining unchanged. The shear failure mode of the salt rock manifested by shear stress-displacement curves tended to be ductile failure with increased normal force. The residual stress of the salt rock was large, indicating its high friction-bearing capacity. The dilatancy deformation was also subjected to shear loading. The fracture section of the salt rock exhibited visible local scratch marks. These experimental results are helpful for further understanding the failure mechanism of salt rock and the stability of underground gas storage under different gas injection and production scenarios.

Epidermolytic acanthoma in a young woman: a case letter

Epidermolytic acanthoma (EA) is a rare benign tumor that is characterized by epidermolytic hyperkeratosis on histopathology.It usually presents in adulthood as an asymptomatic tumor <1 cm in diameter with a verrucous surface. We report a very uncommon case of epidermolytic acanthoma. A 21-year-old woman came to our hospital with a pale black papule on the left lower eyelid near the Inner canthus for 2 months. Two months ago the patient noted a pale brown spot on the inside of the left lower eyelid, which gradually enlarged, forming a papule with a deepened color. There were no associated symptoms, such as itching or pain. There were no local injuries, scratches, or other incidents before the crash occurred. The patient was always healthy, with no history of chronic disease or other skin diseases, and no similar cases existed in the family. We diagnosed it as EA.

The Effects of an Experimental Green Tea Extract Gel on the Surface Roughness of Bleached Teeth with Carbamide Peroxide Gels

Esthetics of the enamel surface is an important factor for a good oral health care. The mastication process could damage the enamel surface by hydroxyapatite layer alteration via local demineralization and micro scratches. We developed an experimental green tea extract gel for enamel restoring treatment. Microstructure features were investigated by SEM microscopy and the surface details were revealed by AFM. The surface roughness and hydroxyapatite grains size and shape were the parameters followed into the investigation. The results show that the best restoring is obtained by the experimental gel leading to surface parameters similar to the healthy enamel better than the values obtained with opalescence carbamide gel.

Orientation-Dependent Deformation Behavior of 316L Steel Manufactured by Laser Metal Deposition and Casting under Local Scratch and Indentation Load.

This study analyzes the local deformation behavior of austenitic stainless steel 316L, manufactured conventionally by casting and additively by laser metal deposition (LMD). We produced directionally solidified 316L specimens with most grains showing (001) orientations parallel to the longitudinal specimen axis. We conducted nanoindentation and scratch experiments for local mechanical characterization and topography measurements (atomic force microscopy and confocal laser scanning microscopy) of indentation imprints and residual scratch grooves for the analysis of the deformation behavior and, in particular, of the pile-up behavior. The local mechanical properties and deformation behavior were correlated to the local microstructure investigated by scanning electron microscopy with energy dispersive X-ray spectroscopy and electron backscatter diffraction analysis. The results show that the local mechanical properties, deformation behavior, and scratch resistance strongly depend on the crystallographic orientation. Nearly (001)-oriented grains parallel to the surface show the lowest hardness, followed by an increasing hardness of nearly (101)- and (111)-oriented grains. Consequently, scratch depth is the greatest for nearly (001)-oriented grains followed by (101) and (111) orientations. This tendency is seen independently of the analyzed manufacturing route, namely Bridgman solidification and laser metal deposition. In general, the laser metal deposition process leads to a higher strength and hardness, which is mainly attributed to a higher dislocation density. Under the investigated loading conditions, the cellular segregation substructure is not found to significantly and directly change the local deformation behavior during indentation and scratch testing.

Influence of Processing Parameters on the Local Scratch Resistance of Cold Sprayed Ti6Al4V Coatings

Ti6Al4V coatings were cold sprayed onto the same bulk alloy at standard conditions, using 800 °C as gas temperature, and a set of new conditions, using 1100°C as gas temperature, which improved coatings performance. Some of these coatings, processed with innovative parameters, were heat treated to promote adhesion and reduce porosity. Scratch tests were performed using a nanoindenter Agilent G200 and the effect of both normal load and scratch velocity were explored. The different mechanisms responsible of wear were evaluated, identifying ploughing and cutting as the main abrasion mechanisms. The wear rate measured in the standard coating was the highest, indicating that this material could not be used to repair the bulk component. However, the abrasion resistance measured in the coatings sprayed at 1100°C was similar to that found in the bulk substrate. Therefore, cold spray could be used for repairing using the new conditions evaluated in this work.

Effect of endometrial scratch using a Pipelle catheter on recurrent implantation failure with intracytoplasmic sperm injection

Back ground In the last two decades, assisted reproductive technology procedures for culturing and transferring embryos have been continually improved, but the clinical pregnancy rate has not improved substantially over the last 10 years. The most important cause for implantation failure is embryo quality or uterine receptivity, but remains unexplained in many cases. About 75% of conceptus are lost before or at the time of implantation. Aim This work aims to assess the effect of endometrial scratch (ES) using a Pipelle catheter on the outcome of intracytoplasmic sperm injection (ICSI) in patients with recurrent implantation failure. Patients and methods The current study included 130 patients who were divided into two equal groups of 65 patients each. In the scratch group, endometrial local scratch using a Pipelle biopsy catheter on the mid luteal phase of spontaneous menstrual cycle before the ICSI procedure was performed, whereas the control group did not undergo ES. ICSI failure was recorded two or more times in each group. Results In the current study, there were no statistically significant differences between the two groups in age, gravidity and parity, type, duration of infertility, and the number of previous ICSI trials. However, the BMI was higher in the control group. In the current study, there were no statistically significant differences between the two groups in basal hormonal profile follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone, prolactin, estradiol, and anti-Mullerian hormone. In this study, there was highly significant increase in the pregnancy rate in the scratch group than the nonscratch group. The number of pregnant cases in the scratch group was 36 (55.4%), whereas in the control group, it was 21 (32.3%), with a highly significant P value of 0.008. In this study, there was no statistically significant difference between positive and negative pregnancy in the basal hormonal profile, except anti-Mullerian hormone and follicle-stimulating hormone levels, P values of 0.040 and 0.000. Conclusion ES in the cycle before the ICSI cycle improved the chemical and clinical pregnancy rates compared with ICSI performed without ES in cases of recurrent implantation failure. It seems that increasing pregnancy rates could be because of the local inflammatory reaction elicited by the endometrial sampling procedure.

Effect of surface morphology of slot-die heads on roll-to-roll coatings of fine PEDOT:PSS stripes

Abstract One of key components in the roll-to-roll slot-die coating system for the fabrication of fine stripes using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) aqueous solution is the slot-die head with a shim and meniscus guide embedded together. We have fabricated the meniscus guide with 150-μm-wide μ-tips using an easily processable film for potential application in solution-based organic light-emitting diodes (OLEDs) displays. However, the success or failure of fine stripe coatings is shown to depend sensitively on the surface morphology of slot-die heads. We have investigated the coating behaviors of two slot-die heads with different surface morphology by changing the configurations of the shim and meniscus guide. Using the slot-die head with good surface roughness but local scratches, it is not feasible to fabricate 100 stripes within the effective coating width of 150 mm. We have demonstrated through computational fluid dynamics (CFD) simulations that the continuous fluid flow is interrupted and thus the fluid velocity is reduced in the presence of scratches, a phenomenon related to coating defects (line breakup and merging). Using the slot-die head with uniformly rough surface but no scratches, however, we can fabricate 150 stripes without defects by reducing the μ-tip length and the shim thickness. It is observed that the inter-stripe width and thickness uniformities are degraded with increasing number of stripes due to the degraded uniformity of the pressure distribution inside the cavity (ink distribution chamber). Finally, we have fabricated OLEDs on the conductive PEDOT:PSS stripes and successfully achieved light emission from 125 OLED stripes.

Influence of exposure at high temperature on the local scratch mechanisms in laser cladded Inconel 625-base metal matrix composite coatings

The mechanisms that characterise the local scratch behaviour of the matrix of an IN625-Cr3C2 composite coating were determined and compared with those of the same Inconel alloy clad. The study was performed for both the coatings in the as-deposited condition and after high-temperature exposure. The coatings were deposited by laser cladding. Scratch tests with a Berkovich sharp indenter were carried out on the surface of the coatings. A model to calculate the volume displaced during the scratch tests was proposed, and the contributions of the four main mechanisms that describe the local scratch behaviour were investigated. The analysis of the results showed that microploughing characterises the IN625 clads behaviour. The formation of M7C3 carbides in the composites' matrix, arising from the partial fusion of the Cr3C2 particles during the deposition, transform the main scratch mechanism into a microcutting process. After exposure at high temperature, microploughing continues to be the main mechanism that describes the IN625 behaviour, but the formation of secondary phases constrains the plastic deformation, increasing the scratch resistance. The behaviour of the composite matrix was affected only by the exposure at the highest temperatures where the local scratch resistance results increased and microcutting remained the most important mechanism.

Cr3C2 incorporation into an Inconel 625 laser cladded coating: Effects on matrix microstructure, mechanical properties and local scratch resistance

There is an increasing industrial demand for metal alloys with high wear resistance under severe operating conditions. Ni-based alloys, such as Inconel superalloys, are an excellent option for these applications; however, their use is limited by their high cost. Ni-based coatings deposited onto carbon steel substrates are being developed to achieve desired surface properties with reduced cost. Laser cladding deposition has emerged as an excellent method for processing Ni based coatings. In this work, microstructure, mechanical properties and local wear behaviour have been investigated in response to the addition of Cr3C2 ceramic particles into an Inconel 625 alloy deposited onto a ferritic steel substrate by laser cladding. Using this deposition technique, a homogeneous distribution of Cr3C2 particles was observed in the coating microstructure. The addition of ceramic particles to the starting powder resulted in the formation of hard precipitates in the coating microstructure. The partial dissolution of Cr3C2 particles during the laser cladding process increased the hardness of the Inconel 625 matrix. Depth sensing indentation and scratch tests were performed to study the local wear behaviour and scratch resistance of the cermet matrix compared with the conventional Inconel 625 alloy. Finally, the effect of Cr3C2 on mechanical properties was correlated with the observed microstructure modifications.

The Effect of Flashcache and Bcache on I/O Performance

Solid state drives (SSDs) provide significant improvements in random I/O performance over traditional rotating SATA and SAS drives. While the cost of SSDs has been steadily declining over the past few years, high density SSDs continue to remain prohibitively expensive when compared to traditional drives. Currently, 1 TB SSDs generally cost more than USD $1,000, while 1 TB SATA drives typically retail for under USD $100. With ever-increasing x86_64 server CPU core counts, and therefore job slot counts, local scratch space density and random I/O performance have become even more important for HEP/NP applications.Flashcache and Bcache are Linux kernel modules which implement caching of SATA/SAS hard drive data on SSDs, effectively allowing one to create hybrid SSD drives using software. In this paper, we discuss our experience with Flashcache and Bcache, and the effects of this software on local scratch storage performance.

A Combined Electrochemical Impedance Spectroscopy and X-Ray-Computed Tomography Study of the Effect of a Silyl Ester on Delamination and Underfilm Pit Formation in a Coated AA7050 Sample

Recently, encapsulated silyl esters have been shown to act as efficient healing agents for self-healing anticorrosive coatings. While the positive protective effects were irrefutable, the actual protection mechanism has not been clarified yet. In the present proof-of-concept study, x-ray-computed μ-tomography and electrochemical impedance spectroscopy (EIS) have been combined to clarify the protection mechanisms of a silyl ester on a coated aluminum alloy (AA)7050 (UNS A97050). The results show that the silyl ester protects the damaged coating-metal system by delaying the delamination initiation and growth kinetics while at the same time decreasing the underfilm pit growth. The study demonstrates the potential of x-ray-computed μ-tomography to follow delamination front line and underfilm pits in coated metallic samples. The combination of tomography with EIS led to an improvement in the understanding of the two mechanisms by which the silyl ester prolongs the protection in the event of local scratch damage.

Electrogenerated Chemiluminescence of Pure Polymer Films and Polymer Blends

We recently reported the discovery of soliton-like electrogenerated chemiluminescence (ECL) waves from pure conjugated polymer films and gold-nanoparticles-doped polymer films. In addition to a more detailed study of these polymer systems by changing the film thickness and the distribution of local leaks, we also apply the ECL wave phenomenon to polymer blends of conjugated and nonconjugated polymers. Poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) is used as the active material that is oxidized and produces ECL with the presence of a co-reactant, tri-n-propylamine (TPA). Several factors such as film thickness, artificial leaks, and solubility of doped polymers are examined for their effects on the ECL behavior. When polystyrene (PS), less soluble in the electrolyte, is blended with F8BT, dotted ECL signals are observed and transported as waves. When poly(methyl methacrylate) (PMMA), more soluble in the electrolyte, is blended with F8BT, PMMA serves as local scratches and ECL waves are triggered simultaneously from the whole film.

Bone Marrow Cell Differentiation Induced by Mechanically Damaged Osteocytes in 3D Gel-Embedded Culture

Osteocytes are suggested to have a crucial role in the initial resorptive phase of bone turnover after microdamage. To study the role of osteocytes in targeted remodeling, we developed an in vitro model, in which osteocytes can be locally damaged and their interactions with bone marrow cells studied. Our results show that the damaged osteocytes activate the osteoclast precursors by soluble factors and thus can control the initial phase of targeted remodeling. Microdamage in bone contributes to fractures and acts as a stimulus for bone remodeling. Besides the targeted remodeling, some remodeling may also be random to serve metabolic purposes. Osteocytes have been considered to provide a crucial role in the activation of osteoclastic bone resorption adjacent to the damaged site. This study was aimed to develop a relevant in vitro model of the targeted remodeling and to show that damaged osteocytes can induce the initial bone resorptive stage. We developed a new device, in which osteocyte-like cell line MLO-Y4 cells were 3D cultured, subjected to local scratching, and assayed for cell viability. NIH3T3-3 cells were used as a control. Bone marrow cells were cultured on the top of the mechanically damaged MLO-Y4 cells, and the formation of TRACP+ cells was assayed. Additionally, the conditioned medium from scratched cultures was added to bone marrow cultures, and the TRACP activity in cell lysates was quantified. The macrophage-colony stimulating factor (M-CSF) and RANKL secretion in the conditioned medium was assayed by ELISA. Scratching induced the death of MLO-Y4 cells. When bone marrow cells were cultured over the gel-embedded MLO-Y4 cells, the application of mechanical scratching induced TRACP+ cell differentiation on gel surface. The cells with TRACP+ could be observed in the very restricted region along the scratching path. Additionally, mechanically damaged osteocytes secreted M-CSF and RANKL, and the conditioned medium showed the potential to induce TRACP+ cells in bone marrow culture. These findings indicate that soluble factors secreted from damaged osteocytes can locally induce and activate the initial phase of osteoclastic cell formation. This study directly shows the association between the damaged osteocytes and the initiation of resorptive stage in bone remodeling.

Prefetching over a network

We discuss CTIP, an implementation of a network filesystem extension of the successful TIP informed prefetching and cache management system. Using a modified version of TIP in NFS client machines (and unmodified NFS servers). CTIP takes advantage of application-supplied hints that disclose the application's future read accesses. CTIP uses these hints to aggressively prefetch file data from an NFS file server and to make better local cache replacement decisions. This prefetching hides disk latency and exposes storage parallelism. Preliminary measurements that show CTIP can reduce execution time by a ratio comparable to that obtained with local TIP over a suite of I/O-intensive hinting applications. (For four disks, the reductions in execution time range from 17% to 69%). If local TIP execution requires that data first be loaded from remote storage into a local scratch area, then CTIP execution is significantly faster than the aggregate time for loading the data and executing. Additionally, our measurements show that the benefit of CTIP for hinting applications improves in the face of competition from other clients for server resources. We conclude with an analysis of the remaining problems with using unmodified NFS servers.

Model for scanning tunneling optical microscopy: A microscopic self-consistent approach.

A general method based on a microscopic picture of matter is developed in order to describe the optical interaction between a thin dielectric tip and a corrugated sample lighted in total reflection. Such a model is expected to interpret recent images obtained from scanning tunneling optical microscopy (steps, infinite tracks, glass plate with local scratches). The conversion of evanescent waves into homogeneous propagating ones is studied from a molecular-physics perspective (multipolar interactions between each atom of the tip and of the object). Our approach is concerned with the study of subwavelength details lying at the surface of a transparent medium. So, instead of solving the macroscopic Maxwell equations and applying the corresponding boundary conditions at the surface of the tip and of the object, we prefer a microscopic treatment in which the dielectric surrounding is taken into account from a set of dynamical matrices introducing all correlations between each elementary volume inside the object. Relations with experiments are discussed.

Do You Know What a "Martha" Is?

The following brief statement about "Martha" and inguinal adenopathy in grammar school students is made to assist colleagues in mastering the vernacular of this group and also to acquaint them with this etiology of inguinal adenopathy. I recently saw a young man with marked inguinal adenopathy and superficial erythema over his lower abdomen. The specific cause was not apparent and tuberculosis was ruled out. His complete blood cell count was essentially normal. There is no good history for local infection or cat scratch fever.

TICK BITE PYREXIA

From May 2 to June 25, 1943, during Tennessee maneuvers, approximately 2,600 patients were admitted to the wards of our evacuation hospital. Hundreds of these patients presented dermatologic evidence of having been bitten by ticks. The present illness of most of these soldiers was in no way related to the tick bites. Many had symptoms which could readily be attributed to secondary complications of the tick bites, such as dermatitis due to local irritation and scratching, cellulitis, lymphangitis and lymphadenitis resulting from secondary infection. Seven patients were proved to have contracted tularemia, 3 showing a typical clinical course of this disease, the other 4 recognizable only by subsequent diagnostic titers of their serum in agglutinating Pasteurella tularensis. A smaller group of patients was admitted whose essential complaint was fever, with or without chills. Associated symptoms included anorexia, malaise, headache and occasionally abdominal pain and vomiting. Physical examination was essentially negative