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Regulator of TElomere Length Helicase 1 (RTEL1) is a helicase required for telomere maintenance and genome replication and repair. RTEL1 has been previously shown to participate in the nuclear export of small nuclear RNAs. Here we show that RTEL1 deficiency leads to a nuclear envelope destabilization exclusively in cells entering S-phase and in direct connection to origin firing. We discovered that inhibiting protein import also leads to similar, albeit non-cell cycle-related, nuclear envelope disruptions. Remarkably, overexpression of wild-type RTEL1, or of its C-terminal part lacking the helicase domain, protects cells against nuclear envelope anomalies mediated by protein import inhibition. We identified distinct domains in the C-terminus of RTEL1 essential for the interaction with KPNB1 (importin β) and NUP153, respectively, and we demonstrated that, on its own, the latter domain can promote the dynamic nuclear internalization of peptides that freely diffuse through the nuclear pore. Consistent with putative functions exerted in protein import, RTEL1 can be visualized on both sides of the nuclear pore using high-resolution microscopy. In all, our work points to an unanticipated, helicase-independent, role of RTEL1 in connecting both nucleocytoplasmic trafficking and nuclear envelope integrity to genome replication initiation in S-phase. [ABSTRACT FROM AUTHOR]

The paper investigates the effects of DC plasma nitriding on surface roughness, hardness, microstructure, micro-abrasion, and corrosion resistance of AISI 316L Austenitic Stainless (AS) steel. The nitriding has been conducted for durations ranging from 4 to 24 h at a temperature of 430 °C in a commercial vacuum furnace, Rübig PN90/70. Micro-abrasion resistance has been tested using the calotest device with a measurement diameter of craters produced on the sample surface after 10 to 60 s of wear. Corrosion resistance has been tested using the Electroimpedance Spectroscopy (EIS) method in a 3.5% NaCl water solution. The surface roughness parameters and hardness of the samples increased with longer nitriding times, attributed to the saturation of austenite and the formation of iron and chromium nitrides. Nitriding for longer than 8 h resulted in the formation of a thicker compound layer that is hard and brittle, leading to reduced wear resistance compared with shorter nitriding times. EIS measurements revealed that nitrided samples had lower corrosion resistance compared with the untreated sample. The corrosion stability was not significantly affected by nitriding time. Different nitriding times have a great influence on resistance to pitting corrosion. This study provides valuable insights into the effects of plasma nitriding on the properties of AS steel, highlighting the importance of optimizing nitriding parameters for specific applications. [ABSTRACT FROM AUTHOR]

Simple Summary: Several procedures have been developed to infer cell-cycle time and the duration of the cycle phases, including tritiated thymidine autoradiography and the immunodetection of thymidine analogues after their incorporation into replicating DNA. These methods have supplied important insights to reveal, on fixed tissue sections and using light or electron microscopy, the proliferative behavior of different cell types under different experimental contexts. Thymidine analogous labeling has provided knowledge about cell growth kinetics that would never have been obtained by histological methods alone. Tritiated thymidine autoradiography, 5-bromo-2′-deoxyuridine (BrdU) 5-chloro-2′-deoxyuridine (CldU), 5-iodo-2′-deoxyuridine (IdU), and 5-ethynyl-2′-deoxyiridine (EdU) labeling have been used for identifying the fraction of cells undergoing the S-phase of the cell cycle and to follow the fate of these cells during the embryonic, perinatal, and adult life in several species of vertebrate. In this current review, I will discuss the dosage and times of exposition to the aforementioned thymidine analogues to label most of the cells undergoing the S-phase of the cell cycle. I will also show how to infer, in an asynchronous cell population, the duration of the G1, S, and G2 phases, as well as the growth fraction and the span of the whole cell cycle on the base of some labeling schemes involving a single administration, continuous nucleotide analogue delivery, and double labeling with two thymidine analogues. In this context, the choice of the optimal dose of BrdU, CldU, IdU, and EdU to label S-phase cells is a pivotal aspect to produce neither cytotoxic effects nor alter cell cycle progression. I hope that the information presented in this review can be of use as a reference for researchers involved in the genesis of tissues and organs. [ABSTRACT FROM AUTHOR]

Low-temperature thermochemical treatments are particularly suitable for use in the surface hardening of austenitic stainless steels without impairing their corrosion resistance. In fact, when using treatment media rich in nitrogen and/or carbon at relatively low temperatures (<450 °C for nitriding, <550 °C for carburizing), it is possible to inhibit the formation of chromium compounds and obtain modified surface layers that consist mainly of a supersaturated solid solution, known as expanded austenite or S-phase. It has been observed that this hard phase allows the enhancement of corrosion resistance in chloride-ion-containing solutions, while the results were contradictory for chloride-free acidic solutions. This overview aims to discuss the corrosion behavior of low-temperature-treated austenitic stainless steels, taking into account the different microstructures and phase compositions of the modified layers, as well as the different test environments and conditions. In particular, the corrosion behavior in both chloride-ion-containing solutions and chloride-free solutions (sulfuric acid, sulfate and borate solutions) is discussed. The analysis of the international literature presents evidence that the microstructure and phase composition of the modified layers have key roles in corrosion resistance, especially in sulfuric acid solutions. [ABSTRACT FROM AUTHOR]

Two surface modification techniques, the glow discharge plasma nitriding (GDPN) and the cathodic cage plasma nitriding (CCPN), were compared regarding the mechanical and tribological behavior of layers produced on AISI 316 stainless-steel surfaces. The analyses were carried out at the micro/nanoscale using nanoindentation and nanoscratch tests. The nitriding temperature (°C) and time (h) parameters were 350/6, 400/6, and 450/6. Morphology, structure, and microstructure were evaluated by X-ray diffraction, scanning electron and optical interferometry microscopies, and energy-dispersive X-ray spectroscopy. GDPN results in stratified modified surfaces, solidly integrated with the substrate, with a temperature-dependent composition comprising nitrides (γ'-Fe4N, ε-Fe2+xN, CrN) and N-solid solution (γN phase). The latter prevails for the low treatment temperatures. Hardness increases from ~2.5 GPa (bare surface) to ~15.5 GPa (450 °C). The scratch resistance of the GDPN-modified surfaces presents a strong correlation with the layer composition and thickness, with the result that the 400 °C condition exhibits the highest standards against microwear. In contrast, CCPN results in well-defined dual-layers for any of the temperatures. A top 0.3–0.8 µm-thick nitride film (most ε-phase), brittle and easily removable under scratch with loads as low as 63 mN, covers a γN-rich case with hardness of 10 GPa. The thickness of the underneath CCPN layer produced at 450 °C is similar to that from GDPN at 400 °C (3 µm); on the other hand, the average roughness is much lower, comparable to the reference surface (Ra ~10 nm), while the layer formation involves no chromium depletion. Moreover, edge effects are absent across the entire sample´s surface. In conclusion, among the studied conditions, the GDPN 400 °C disclosed the best tribo-mechanical performance, whereas CCPN resulted in superior surface finishing for application purposes. [ABSTRACT FROM AUTHOR]

Lattice distortion and amorphization of carbon-doped SUS304 by variation of the laser output were investigated in terms of phase formation and the bonding state. The laser output was changed by 10% in the range of 60% to 100% after covering the SUS304 with carbon paste. A graphite peak and expanded austenite (S-phase) peak were observed in the carbon-doped SUS304, and Rietveld refinement was performed to identify the lattice distortion. The lattice constant of SUS304 was initially 3.612 Å, but expansion lattice distortion occurred in the carbon-doped SUS304 as a result of the S phase formation and carbon doping, and the lattice constant increased to 3.964 Å (100% laser output). X-ray photoelectron spectroscopy analysis for the bonding state of the carbon-doped SUS304 showed that the sp2/sp3 ratio decreased from 3.21 (70% laser output) to 2.52 (100% laser output). The residual stress in the lattice was accumulated due to carbon doping by high thermal energy, which resulted in the formation of amorphous carbon. The bonding environment was represented by the ID/IG ratio using Raman analysis, and it increased from 0.55 (70% laser output) to 1.68 (100% laser output). During microstructure analysis of the carbon-doped SUS304, disordered structures by amorphization were observed in the carbon-doped SUS304 by the greater than 90% laser output. The amorphous carbon filled the lattice grains or voids to lubricate the surface, which improved the friction coefficient and wear rate from 0.23 and 7.63 mm3(Nm)−110−6 to 0.09 and 1.43 mm3(Nm)−110−6, respectively. [ABSTRACT FROM AUTHOR]

Early embryonic cleavages are characterized by short and highly synchronous cell cycles made of alternating S- and M-phases with virtually absent gap phases. In this contracted cell cycle, the duration of DNA synthesis can be extraordinarily short. Depending on the organism, the whole genome of an embryo is replicated at a speed that is between 20 to 60 times faster than that of a somatic cell. Because transcription in the early embryo is repressed, DNA synthesis relies on a large stockpile of maternally supplied proteins stored in the egg representing most, if not all, cellular genes. In addition, in early embryonic cell cycles, both replication and DNA damage checkpoints are inefficient. In this article, we will review current knowledge on how DNA synthesis is regulated in early embryos and discuss possible consequences of replicating chromosomes with little or no quality control. [ABSTRACT FROM AUTHOR]

Low-temperature treatments have become a valuable method for improving the surface hardness of stainless steels, and thus their tribological properties, without impairing their corrosion resistance. By using treatment temperatures lower than those usually employed for nitriding or carburizing of low alloy steels or tool steels, it is possible to obtain a fairly fast (interstitial) diffusion of nitrogen and/or carbon atoms; on the contrary, the diffusion of substitutional atoms, as chromium atoms, has significantly slowed down, therefore the formation of chromium compounds is hindered, and corrosion resistance can be maintained. As a consequence, nitrogen and carbon atoms can be retained in solid solutions in an iron lattice well beyond their maximum solubility, and supersaturated solid solutions are produced. Depending on the iron lattice structure present in the stainless steel, the so-called "expanded austenite" or "S-phase", "expanded ferrite", and "expanded martensite" have been reported to be formed. This review summarizes the main studies on the characteristics and properties of these "expanded" phases and of the modified surface layers in which these phases form by using low-temperature treatments. A particular focus is on expanded martensite and expanded ferrite. Expanded austenite–S-phase is also discussed, with particular reference to the most recent studies. [ABSTRACT FROM AUTHOR]

In order to study the suitability of the S-phase layers as the interlayer for Cr2N chromium nitride coatings, a number of composite coatings were deposited by the reactive magnetron sputtering (RMS) method on austenitic steel substrates with various initial surface conditions (as delivered and polished) and their corrosion resistance was assessed. Coatings with S-phase interlayer were deposited at three different nitrogen contents in the working atmosphere (15%, 30%, and 50%), which influenced the nitrogen concentration in the S-phase. Coatings with chromium, as a traditional interlayer to improve adhesion, and uncoated austenitic stainless steel were used as reference materials. Detailed microstructural and phase composition studies of the coatings were carried out by means of scanning electron microscopy (SEM), optical microscopy (LM), and X-ray diffraction (XRD) and were discussed in the context of results of corrosion tests carried out with the use of the potentiodynamic polarization method conducted in a 3% aqueous solution of sodium chloride (NaCl). The performed tests showed that the electrochemical potential of the S-phase/Cr2N composite coatings is similar to that of Cr/Cr2N coatings. It was also observed that the increase in the nitrogen content in the S-phase interlayer causes an increase in the polarization resistance of the S-phase/Cr2N composite coating. Moreover, with a higher nitrogen content in the S-phase interlayer, the polarization resistance of the S-phase/Cr2N coating is higher than for the Cr/Cr2N reference coating. All the produced composite coatings showed better corrosion properties in relation to the uncoated austenitic stainless steel. [ABSTRACT FROM AUTHOR]

Austenitic steels are characterized by their outstanding corrosion resistance. They are therefore suitable for a wide range of surface protection requirements. The application potential of these stainless steels is often limited by their poor wear resistance. In the field of wrought alloys, interstitial surface hardening has become established for simultaneously acting surface stresses. This approach also offers great potential for improvement in the field of coating technology. The hardening of powder feedstock materials promises an advantage in the treatment of large components and also as a repair technology. In this work, the surface hardening of AISI 316L powder and its processing by thermal spraying is presented. A partial formation of the metastable expanded austenitic phase was observed for the powder particles by low-temperature gas nitrocarburizing. The successful deposition was demonstrated by cold gas spraying. The amount of expanded austenitic phase within the coating structure strongly depends on the processing conditions. Microstructure, corrosion and wear behavior were studied. Process diagnostic methods were used to validate the results. [ABSTRACT FROM AUTHOR]

Low-temperature nitriding allows to improve surface hardening of austenitic stainless steels, maintaining or even increasing their corrosion resistance. The treatment conditions to be used in order to avoid the precipitation of large amounts of nitrides are strictly related to alloy composition. When nickel is substituted by manganese as an austenite forming element, the production of nitride-free modified surface layers becomes a challenge, since manganese is a nitride forming element while nickel is not. In this study, the effects of nitriding conditions on the characteristics of the modified surface layers obtained on an austenitic stainless steel having a high manganese content and a negligible nickel one, a so-called nickel-free austenitic stainless steel, were investigated. Microstructure, phase composition, surface microhardness, and corrosion behavior in 5% NaCl were evaluated. The obtained results suggest that the precipitation of a large volume fraction of nitrides can be avoided using treatment temperatures lower than those usually employed for nickel-containing austenitic stainless steels. Nitriding at 360 and 380 °C for duration up to 5 h allows to produce modified surface layers, consisting mainly of the so-called expanded austenite or γN, which increase surface hardness in comparison with the untreated steel. Using selected conditions, corrosion resistance can also be significantly improved. [ABSTRACT FROM AUTHOR]

In order to study the suitability of the S-phase layers as the interlayer for Cr 2 N chromium nitride coatings, a number of composite coatings were deposited by the reactive magnetron sputtering (RMS) method on austenitic steel substrates with various initial surface conditions (as delivered and polished) and their corrosion resistance was assessed. Coatings with S-phase interlayer were deposited at three different nitrogen contents in the working atmosphere (15%, 30%, and 50%), which influenced the nitrogen concentration in the S-phase. Coatings with chromium, as a traditional interlayer to improve adhesion, and uncoated austenitic stainless steel were used as reference materials. Detailed microstructural and phase composition studies of the coatings were carried out by means of scanning electron microscopy (SEM), optical microscopy (LM), and X-ray diffraction (XRD) and were discussed in the context of results of corrosion tests carried out with the use of the potentiodynamic polarization method conducted in a 3% aqueous solution of sodium chloride (NaCl). The performed tests showed that the electrochemical potential of the S-phase/Cr 2 N composite coatings is similar to that of Cr/Cr 2 N coatings. It was also observed that the increase in the nitrogen content in the S-phase interlayer causes an increase in the polarization resistance of the S-phase/Cr 2 N composite coating. Moreover, with a higher nitrogen content in the S-phase interlayer, the polarization resistance of the S-phase/Cr 2 N coating is higher than for the Cr/Cr 2 N reference coating. All the produced composite coatings showed better corrosion properties in relation to the uncoated austenitic stainless steel.

AISI 316L steel was subjected to active screen plasma nitriding and nitrocarburising. The processes were carried out at 440 °C for 6 h. The nitriding process employed an atmosphere of nitrogen and hydrogen, while nitrocarburising was carried out in nitrogen, hydrogen and methane. The processes yielded structures consisting of nitrogen and nitro-carbon expanded austenite, respectively. Microhardness was measured via the Vickers method, surface roughness using an optical profilometer, microstructure by means of light microscopy, while a scanning electron microscope (SEM) served to determine surface topography. Phase composition, lattice parameter and lattice deformation tests were carried out using the X-ray diffraction (XRD) method. Corrosion resistance measurements were performed in a 0.5 M NaCl solution using the potentiodynamic method. The produced layers showed very high resistance to pitting corrosion, while the pitting potential reached 1.5 V, a value that has not yet been recorded in a chloride environment. After the passive layer was broken down, there was a clear deceleration of pitting in the nitrocarburised layer. It was found that in the case of nitro-carbon expanded austenite, pits are formed much slower compared to the nitrogen austenite layer. [ABSTRACT FROM AUTHOR]

This paper presents the results of microstructural examinations on gas carbonitrided layers using scanning electron microscopy (SEM), wavelength dispersive spectrometry X-ray microanalysis (WDS), magnetic force microscopy (MFM), electron backscattered diffraction (EBSD), and X-ray diffraction. The main objective of the work is to discuss the microstructural and morphological changes occurring in the layers depending on the process parameter such as temperature and atmosphere composition. The carbonitrided layers comprise two sublayers: an outer layer enriched in nitrogen and an inner layer enriched in carbon. It is found that both the microstructure and the thickness depend on the technological parameters of the thermochemical treatment. The treatment temperature is particularly important, increasing both the total and the nitrogen-rich sublayer thickness regardless of the atmosphere type. The nitrogen potential has a positive influence on the thickness of the nitrogen-stabilised S-phase sublayer. Layers treated for 5 h at temperatures of 400 and 450 °C are composed of an internal carbon-enriched S-phase sublayer and an outer nitrogen-enriched S-phase sublayer that can be divided into ferromagnetic and paramagnetic zones. In the outer sublayer, symmetry distortion of the fcc crystal system is observed and stacking faults may have occurred. With layers produced at 500 °C for 5 h, the outer nitrogen-enriched sublayer contains fine precipitates of nitrides and carbides. [ABSTRACT FROM AUTHOR]

Gas nitriding is known as a convenient process to improve the wear resistance of steel components. A precipitation-free hardening by low-temperature processes is established to retain the good corrosion resistance of stainless steel. In cases of thermal spray coatings, the interstitial solvation is achieved without an additional surface activation step. The open porosity permits the penetration of the donator media and leads to a structural diffusion. An inhomogeneous diffusion enrichment occurs at the single spray particle edges within the coating's microstructure. A decreasing diffusion depth is found with increasing surface distance. The present study investigates an adjusted process management for low-temperature gas nitriding of high velocity oxy-fuel-sprayed AISI 316L coatings. To maintain a homogeneous diffusion depth within the coating, a pressure modulation during the process is studied. Additionally, the use of cracked gas as donator is examined. The process management is designed without an additional surface activation step. Regardless of surface distance, microstructural investigations reveal a homogeneous diffusion depth by a reduced processing time. The constant hardening depth allows a reliable prediction of the coatings' properties. An enhanced hardness and improved wear resistance is found in comparison with the as-sprayed coating condition. [ABSTRACT FROM AUTHOR]

A solution-hardening of AISI 316L stainless-steel powder was conducted. The expansion of the crystal lattice and a strong increase in the nanoindentation hardness confirm the successful diffusion of carbon and nitrogen in the interstices. A multiphase state of the powder feedstock with phase fractions of the metastable S-phase (expanded austenite) mainly at the particle's edge, and the initial austenitic phase within the core was found. Thermal spraying using high velocity oxy-fuel (HVOF) and atmospheric plasma spraying (APS) prove the sufficient thermal stability of the S-phase. Microstructural investigations of the HVOF coating reveal the ductility of the S-phase layer, while the higher heat load within the APS cause diffusion processes with the initial austenitic phase. The lattice expansion and the nanoindentation hardness decrease during thermal spraying. However, the absence of precipitates ensures the sufficient heat stability of the metastable S-phase. Even though further efforts are required for the thermochemical treatment of powder feedstock, the results confirm the feasibility of the novel powder treatment approach. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel exhibits an excellent corrosion behavior. The relatively poor wear resistance can be improved by surface hardening, whereby thermochemical processes offer an economic option. The successful diffusion enrichment of bulk material requires a decomposition of the passive layer. A gas nitriding of high velocity oxygen fuel spraying (HVOF)-sprayed AISI 316L coatings without an additional activation step was studied with a variation of the process temperature depending on the heat-treatment state of the coating. A successful nitrogen enrichment was found in as-sprayed condition, whereas passivation prevents diffusion after solution heat treatment. The phase composition and microstructure formation were examined. The crystal structure and lattice parameters were determined using X-ray diffraction analysis. The identified phases were assigned to the different microstructural elements using the color etchant Beraha II. In as-sprayed condition, the phase formation in the coating is related to the process temperature. The formation of the S-phase with interstitial solvation of nitrogen is achieved by a process temperature of 420 °C. Precipitation occurs during the heat treatment at 520 °C. In both cases, a significant increase in wear resistance was found. The correlation of the thermochemical process parameters and the microstructural properties contributes to a better understanding of the requirements for the process combination of thermal spraying and diffusion. [ABSTRACT FROM AUTHOR]

Tribocorrosion damage is a cause for the premature failure of hip implants made of cobalt-based alloys. Low-temperature carburising can be a plausible solution towards mitigating the tribocorrosion damage of articulating components. This diffusion treatment introduces a supersaturated carbon solid solution, termed S-phase, which hardens the CoCrMo alloy without detriment to the corrosion resistance. This work investigates and compares the tribocorrosion behaviour of untreated and carburised ASTM F1537 CoCrMo alloys tested in Ringer's solution using a reciprocating sliding configuration against a polycrystalline alumina counterface under different electrochemical conditions. The research shows that whereas the carburised alloy suffered a slightly higher wear loss under a cathodic potential, it was able to reduce the material losses considerably when tested under both open circuit and anodic potential conditions. Under anodic conditions material losses by corrosion due to wear dominated. The better tribocorrosion resistance of the carburised layer was attributed to the better qualities of the passive film for the carburised sample coupled with an increased load support. [ABSTRACT FROM AUTHOR]