A reverse analysis of the Vickers indentation fracture toughness was carried out to derive a numerical expression for estimating the fracture resistance of the Fe2B layer. The boride layers were ...created at the surface of AISI 1018 borided steels by the paste boriding process, in which a 4-mm-thick layer of boron carbide paste was applied to the material surface. The treatment was carried out at temperatures of 1123–1273K with exposure times of 4, 6 and 8h at each temperature. From the set of experimental conditions used in the boriding process, Vickers indentations were performed with an applied load of 1.96N at 25μm from the surface of the borided steels. The crack lengths created from the corners of the Vickers indentation prints were analyzed in the Palmqvist crack regime. The numerical expression of the stress intensity factor (K) of the Fe2B layer was assisted by both a dimensional analysis and the superposition principle. The analysis considered the residual stress field generated by the indentation load, which was superimposed upon different crack lengths; the stress intensity factor was expressed as a function of the elastic–plastic properties of the layer, the dimensionless crack length, and the location on the Palmqvist crack front.
From an extensive numerical analysis, the results of the fracture toughness (KC) values of the Fe2B layer were estimated with the finite element method, and then compared with the values obtained by traditional Palmqvist crack models proposed by other researchers.
► The fracture toughness of the Fe2B layer was evaluated by the finite element method. ► The model was developed by a dimensional analysis and the superposition principle. ► The resulted values of the boride layer were in good agreement with literature.
Glutathione
S-transferases (GSTs) are enzymes that act in excretion of physiologic and xenobiotic substances, protecting cells against chemical toxicity and stress. In this work, we characterized the ...enzymatic activity of GST in eggs and larvae of cattle tick
Boophilus microplus, on different days after oviposition and eclosion. The results showed that the GST activity varied depending on the time elapsed after oviposition and eclosion. Molecules involved in mechanism of protection from oxidative stress are correlated with the increase in GST activity. The oxygen consumption kinetics showed a positive correlation with the increase in GST activity during embryogenesis. A high content of thiobarbituric acid reactive substances were observed in egg and larva extracts, indicating that ticks face high oxidative stress during embryogenesis and aging. In eggs and larvae, GST activity can be correlated to kinetic parameters of oxidative stress such as catalase and glutathione. In addition, GST activity showed strong positive correlation with lipid peroxidation, an indication that it plays a role in oxidant defences in eggs.
Several studies have already shown that changes in the AR gene may be associated with a more aggressive disease phenotype and even castration-resistant prostate cancer. Thus, we investigated ...cytogenetic and molecular alterations linked to AR.
To evaluate AR methylation, we performed a cytogenetic-molecular analysis using fluorescence in situ hybridization that uses specific probes for the AR gene (Xq11.12) and the X chromosome centromere. For AR activity, we performed a qualitative analysis of human androgen receptor activity. To analyze the expression of AR in PC3 and LNCaP cell lines, we used qPCR assays.
In the qPCR assay, we found downregulation of AR in the PC3 cell line compared with the LNCaP. We found the presence of X chromosome polysomy in PC-3 and LNCaP cell lines by FISH assay. In the HUMARA-Q assay, we found two X chromosomes/cell and the activity of both AR in the PC-3 cell line. In LNCaP cells, we found two X chromosomes/cell and methylation of only one AR.
Castration-resistant prostate cancer phenotype represents a significant challenge in the setting of urological management. The X chromosomes and AR-linked alterations may contribute to a better understanding of the disease. However, further studies should be performed in an attempt to elucidate as much as possible the role of AR in the castration-resistant prostate cancer phenotype.
Diversos estudios han demostrado que los cambios en el gen RA pueden estar asociados a un fenotipo de enfermedad más agresivo e incluso al cáncer de próstata resistente a la castración. Por este motivo, hemos investigado las alteraciones citogénicas y moleculares asociadas al RA.
Para evaluar la metilación del RA, realizamos un análisis citogenético-molecular mediante hibridación fluorescente in situ que utiliza sondas específicas para el gen del RA (Xq11.12) y el centrómero del cromosoma X. Respecto a la actividad del RA, realizamos un análisis cualitativo de la actividad del receptor de andrógenos humano. Para analizar la expresión del RA en las líneas celulares PC3 y LNCaP, utilizamos ensayos de qPCR.
En el ensayo qPCR, encontramos una regulación a la baja del RA en la línea celular PC3 en comparación con la LNCaP. Hallamos la presencia de polisomía del cromosoma X en las líneas celulares PC-3 y LNCaP mediante el ensayo FISH. En el ensayo HUMARA-Q encontramos la presencia de dos cromosomas X/célula y actividad en ambos RA de la línea celular PC-3. En las células LNCaP hallamos la presencia de dos cromosomas X/célula y la metilación de solo un RA.
El fenotipo del cáncer de próstata resistente a la castración representa un gran desafio en el tratamiento urológico. Estos cromosomas X y las alteraciones ligadas al RA pueden contribuir a una mejor comprensión de la enfermedad; sin embargo, deben realizarse más estudios para arrojar más luz sobre el papel del RA en el fenotipo del cáncer de próstata resistente a la castración.
Abstract
New results about the growth kinetics of CoB–Co
2
B layers developed at the surface of CoCrMo alloy using the powder-pack boriding process assisted by a direct current field (PBDCF) were ...estimated in this work. The PBDCF was conducted at temperatures of 1048 – 1148 K with different exposure times for each temperature, whereas the growth kinetics of the cobalt boride layers was modelled using a system of two differential equations. In addition, indentation properties such as hardness, Young’s modulus and residual stresses were estimated along the depth of the borided CoCrMo surface. The growth kinetics of the cobalt boride layers developed by PBDCF indicated that thicker boride layers were formed on the material’s surface which was in contact to the current field at the anode, in contrast to the surface exposed at the cathode. The kinetics of cobalt boride layers were compared with those obtained by conventional powder-pack boriding process.
Indentation size effect on the Fe2B/substrate interface Campos-Silva, I.; Hernández-Sánchez, E.; Rodríguez-Castro, G. ...
Surface & coatings technology,
12/2011, Letnik:
206, Številka:
7
Journal Article, Conference Proceeding
Recenzirano
This study evaluated the indentation size effect on the Fe2B/substrate interface using the Berkovich nanoindentation technique. First, the Fe2B layers were obtained at the surface of AISI 1018 ...borided steels by the powder-pack boriding method. The treatment was conducted at temperatures of 1193, 1243 and 1273K for 4, 6 and 8h at each temperature. The boriding of AISI 1018 steel resulted in the formation of saw-toothed Fe2B surface layers. The formation of a jagged boride coating interface can be attributed to the enhanced growth at the tips of the coating fingers, due to locally high stress fields and lattice distortions. Thus, the mechanical properties achieved at the tips of the boride layer are of great importance in the behavior of borided steel.
Applied loads in the range of 10 to 500mN were employed to characterize the hardness in the tips of the Fe2B/substrate interface for the different conditions of the boriding process. The results showed that the measured hardness depended critically on the applied load, which indicated the influence of the indentation size effect (ISE). The load-dependence of the hardness was analyzed with the classical power-law approach and the elastic recovery model. The true hardness in the tips of the Fe2B/substrate interface was obtained and compared with the boriding parameters. Finally, the nanoindentation technique was used to estimate the state of residual stresses in this critical zone of the Fe2B/substrate interface.
► Nanoindentation measurements were performed in the tips of the Fe2B layer. ► Indentation size effect was observed in the needles of the surface layer. ► The nature of residual stresses in the tips of the boride layer was compressive.
A simple diffusion model is proposed to estimate the growth kinetics of Fe
2
B layers created at the surface of pure iron. This model employs the mass balance equation at the Fe
2
B/substrate ...interface to evaluate the boron diffusion coefficient (D
Fe
2
B
) in the boride layer. The Fe
2
B layers were formed using the paste boriding process, at four temperatures with different exposure times. Analysing the results, the evolution of the parabolic growth constant (k) of the Fe
2
B layer is presented as a function of boron concentration and boride incubation time t
0
(T). Furthermore, the instantaneous velocity of the Fe
2
B/substrate interface and the weight gain of borided pure iron were estimated for different boriding temperatures. Finally, to validate the diffusion model, the boride layer thicknesses were predicted and experimentally verified for two boriding temperatures and for different treatment times.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A 54-year-old woman was diagnosed with infiltrative ductal breast carcinoma. Two years after treatment, the patient developed an acute myeloid leukemia (AML) which harbored del(11q23) in 8% of the ...blast cells. The patient was submitted for allogeneic stem cell transplantation (aSCT) from her HLA-compatible sister. Ten months after transplantation, she relapsed with an AML with basophilic maturation characterized by CD45(low) CD33(high), CD117⁺, CD13(-/+), HLA Dr(high), CD123(high), and CD203c⁺ blast cells lacking expression of CD7, CD10, CD34, CD15, CD14, CD56, CD36, CD64, and cytoplasmic tryptase. Karyotype analysis showed the emergence of a new clone with t(2;14) and FISH analysis indicated the presence of MLL gene rearrangement consistent with del(11q23). Interestingly, AML blast cell DNA tested with microsatellite markers showed the same pattern as the donor's, suggesting that this AML emerged from donor cells. Additionally, polymorphisms of the XPA, XPD, XRCC1, XRCC3 and RAD51 DNA repair genes revealed three unfavorable alleles with low DNA repair capacity.In summary, we report the first case of AML involving XPD and XRCC3 polymorphisms from donor origin following allogeneic stem cell transplantation and highlight the potential need for careful analysis of DNA repair gene polymorphisms in selecting candidate donors prior to allogeneic stem cell transplantation.
In this paper, significant results about the evaluation of the influence of wear test factors such as load, distance, and sliding speed are analyzed to determine the statistical behavior of the ...specific wear rate, depth, and friction coefficient as response variables. Dry sliding wear tests were performed on the borided AISI 316L stainless steel under controlled environmental conditions, according to the ASTM G133-05 standard procedure, and a UMT-2 universal tester was used. The development of the analysis of variance showed that the load factor has the major statistical significance on the specific wear rate, depth, and CoF with 63.7%, 59.60%, and 62.67%, respectively. The response surface methodology was applied through the distance weighted least-squares fitting to explain the behavior of the response variables on the measured variables and the difference in the performance due to the total distance of sliding.
Display omitted
•Dry sliding wear statistical analysis on borided AISI 316L stainless steel under ball-on-flat tests was investigated.•The load factor has the major statistical significance with 63.7% on the specific wear rate.•A full factorial design randomized experiment approach was applied to study the test factors and levels.•RSM with DWLS was applied to obtain 2D maps of the response variables.
In this study the corrosion resistances of AISI 1018 and AISI 304 borided and non-borided steels were estimated using polarization resistance and electrochemical impedance spectroscopy (EIS) ...techniques. Boriding of the steel samples was conducted using the powder-pack method at 1223 K with 6 h of exposure. Structural examinations of the surfaces of the borided steels showed the presence of a Fe
2
B layer with isolated FeB teeth on the AISI 1018 steel, whereas a compact layer of FeB/Fe
2
B was formed on the AISI 304 steel. Polarization resistance and EIS of the borided and non-borided steels surfaces were performed in a corrosive solution of 1 M HCl. The EIS data were analyzed during 43 days of exposure to the acid solution. Impedance curves obtained during this period for the borided and non-borided steels were modeled using equivalent electrical circuits. The results of both electrochemical techniques indicated that boride layers formed at the steel surfaces effectively protect the samples from the corrosive effects of HCl. The main corrosion processes observed on the boride layers were pitting and crevice corrosion.
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