This work studies the tribological behavior of the 316L austenitic stainless steels alloyed with boron produced by conventional powder metallurgy process. Boron effect was investigated in terms of ...densification, microstructure, hardness, friction and wear behavior. 316L samples were prepared with 0.6 wt% and 0.8 wt% of boron. The microstructure of the sintered samples was examined by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS). The friction and wear behavior of the sintered materials was investigated using dry reciprocating sliding wear tests. Boron additions result in the formation of intergranular borides in the microstructure of the sintered 316L steel. The material densification is favored by the development of a liquid phase during sintering, promoting an increase in hardness and wear resistance of the 316L steel. No change in friction coefficient was obtaining with boron addition. The low plasticity index of the boride and the high dynamic sliding hardness of the boron-containing sample are responsible for the considerable reduction in the specific wear coefficient. Plasticity-dominated sliding wear by adhesive transfer and mild oxidative wear by metallic particle oxidation were the predominant wear mechanism in the worn surfaces of all sintered samples under dry reciprocating conditions.
•The specific wear coefficient of 316L decreases with the increase in boron content.•Besides low porosity, the boron-alloyed 316L exhibits rounded and small pores.•Hard borides decrease the intensity of material removal by adhesive wear.•Borides change the sliding dynamic hardness and the plasticity index of 316L.
Copper‑beryllium alloys are widely used to manufacture thermoplastics injection molds due to their high thermal conductivity. Even though these alloys admit precipitation hardening at temperatures ...between 250 and 400 °C, they still call for surface coatings to enhance their abrasion resistance. However, application of these coatings can generate over-aging under specific deposition temperature ranges. This phenomenon causes a loss of substrate mechanical properties, making some industrial applications unfeasible, for example: construction of core pins with high slenderness ratio, and cores and cavities injection mold with narrow closure regions. This work proposes a solution to increase abrasive wear resistance of copper‑beryllium alloy C17200 through an electroless nickel‑phosphorus (NiP) coating. Temperature used in heat treatment of the coating was lower than substrate aging temperature. In this work, the heat treatment was carried out at 200 °C for 24 h. Hardness of coating and substrate was evaluated by measuring the cross-sectional microhardness profile after heat treatment. Microstructure, chemical composition, and crystallinity of coating and substrate were characterized using scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GD-OES), and X-ray diffraction (XRD), respectively. Wear behavior of coating-substrate systems was evaluated by micro-abrasive wear tests optical profilometry and SEM. NiP coating combined with heat treatment increased the surface hardness from 340 HV for uncoated alloy to an average of 997 HV for coated and heat treated alloy while maintaining substrate hardness. The application of this coating reduced the wear coefficient in the order of 3.03 × 10−6 to 2.04 × 10−6 (mm3 N−1 m−1). All the conditions analyzed, showed a mixed micro-abrasive wear mechanism with rolling and grooving wear characteristics.
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•Electroless nickel-phosphorus (NiP) coating applied on CuBe alloy C17200.•Coating process temperature lower than copper‑beryllium alloy aging temperature.•Coating NiP combined with heat treatment reduce the wear coefficient.•Increased wear resistance of CuBe alloy without changing substrate properties.
Pure MoSx and MoSx + Hf thin films were deposited by magnetron sputtering and characterized by RBS, GAXRD, XPS, high temperature oxidation tests and tribological tests. Hf content was set at 12 at.% ...by RBS and GAXRD analyses revealed a complete amorphization caused by Hf incorporation. XPS analyses indicated that hafnium is inserted in MoSx in the form of HfSx, moreover, such compound was responsible for inhibiting the formation of MoS. These factors are closely correlated with improvements obtained in oxidation resistance, friction coefficient, wear rate and lifespan of MoSx thin films.
•MoSx and MoSx + Hf thin films were deposited by magnetron sputtering.•Hafnium incorporation promotes a complete amorphization of the coating.•Hafnium atoms are present in the MoSx matrix as HfSx structure.•It was observed MoS structure only for pure MoSx coatings.•MoSx + Hf coating possess better tribological properties when compared to MoSx.
This work presents a study of the mechanical and tribological properties of niobium-alumina composites obtained by the spark plasma sintering with a uniaxial pressure of 50 MPa at 1400 °C. The ...microstructure and crystalline phases of sintered materials were determined by scanning electron microscopy and X-ray diffraction, respectively. Mechanical properties of the samples related to the stiffness, hardness, and fracture toughness were determined through the instrumented indentation and the Vickers indention tests. For the tribological study, alumina, alumina-15%Nb, and alumina-25%Nb materials were tested under dry reciprocating sliding conditions, at room temperature using a ball-on-disc configuration. A three-levels factorial design was used to conduct the wear tests, considering the combination of material compositions and applied load (5 N, 10 N, and 15 N of applied load) for two types of counterbody (52100 steel and Al2O3). Niobium addition improved the fracture toughness and wear resistance of the alumina matrix composites. The index of brittleness that correlates the stiffness, hardness and fracture toughness of the materials decreased with niobium content. When sliding against the steel counterbody, composites exhibited a wear resistance two orders of magnitude higher than that of the monolithic alumina and specific wear rate values characteristic of the mild wear regime (k lower than 10−6 mm3 (N m)−1). The higher wear resistance of composites was related to the tribofilm formation on worn surfaces, due to material transfer from the 52100 steel counterbody surface. Alumina showed a higher wear rate in comparison with niobium-containing composites, due to brittle fracture occurrence, mostly when sliding against the Al2O3 counterbody at higher loads. Wear-regime maps as a function of the index of brittleness and severity of contact allowed the distinction of wear mechanisms of the studied materials and visualization of the improved wear resistance of the niobium-alumina composites.
Thirty-two patients with clinical node-negative breast cancer underwent sentinel node localization study as part of a National Cancer Institute-sponsored multicenter trial. Anatomical and ...histopathologic characteristics of sentinel lymph node (SLN) and a kinetic analysis of nodal uptake were studied. Patients were injected with 1 mCi/4 ml unfiltered 99mTc-sulfur colloid in four divided doses around the palpable lesion or immediately adjacent to the excision cavity if prior biopsy was performed. SLN biopsy was performed 1.5-6 hr (mean = 3 hr) postinjection. Intraoperative localization was performed using a gamma probe. All patients underwent complete axillary dissection.
SLN was identified in 30 of 32 (94%) patients. There were no false-negative SLN biopsies.
This study supports the clinical validity of SLN biopsy in breast cancer and confirms that, unlike the blue dye technique, the learning curve with unfiltered 99mTc-sulfur colloid and the gamma detection probe is short, and SLN localization is achievable in over 90% of cases by surgeons with modest experience. The use of unfiltered 99mTc-sulfur colloid (larger particle size) with larger injected volume permits effective localization of SLNs.
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•The HA/β-CD inclusion complex was prepared and characterized.•β-CD enhance the anti-hyperalgesic effect of HA.•Anti-hyperalgesic effect of HA/β-CD seems to be mediated by the opioid ...system.
Hecogenin acetate (HA), a steroidal acetylated-sapogenin, has an analgesic profile already assigned, but its low water solubility and short half-life limit its use in chronic conditions. β-cyclodextrin (β-CD) can improve the chemical and pharmacological property of nonpolar compounds such as HA. Therefore, a HA complexed with β-CD (HA-CD) was prepared and characterized by thermal, morphological and spectroscopic analysis. A model of chronic musculoskeletal pain was induced by means of two injections of pH 4.0 saline (20μL) into the left gastrocnemius 5days apart was used. After confirming hyperalgesia, male mice were treated with HA, HA-CD (20mg/kg; p.o.) or vehicle (saline 0.9%, p.o.). Motor coordination tests, substance P (SP) levels in a lumbosacral (L4-S2) spinal cord sample and a docking study were equally assessed to check for a possible action on the opioid receptors. Oral pretreatment with HA or HA-CD produced a significant antinociceptive (p<0.01) profile and also decreased mechanical hyperalgesia, with HA-β-CD showing significantly better effects when compared to HA alone (p<0.05). The interaction between HA and the opioid receptor (MU, Kappa, Delta) was corroborated by the docking study. Moreover, the SP level was reduced in a spinal cord sample. Our findings suggest that β-CD can improve the anti-hyperalgesic effect of HA in an animal model of musculoskeletal pain.
We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron ...laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs.
Localizing positron emission tomography (PET)/computed tomography (CT) findings in heavily scarred surgical fields can be challenging. A high energy gamma probe (PET probe) can be used to guide ...surgery in those difficult areas. We describe our experience localizing and removing fluorodeoxyglucose (FDG) avid lesions in different body areas. Between 2004 and 2007, we used the PET probe to localize and remove 12 lesions from 9 patients. The lesions were removed confirming ex vivo and tumor bed FDG activity. Five patients had lesions in previously operated and sometimes radiated fields. One patient had FDG avid spots in the retroperitoneum. Two lymphoma patients had been previously treated and had new FDG avid spots in a background of scarred nodes. The last patient had a core biopsy suspicious for lymphoma but a repeat CT was non-specific. One patient with gastric cancer patient, two patients with melanoma patients and two patients with breast cancer had 10 metastatic lesions easily identified and removed. After a median follow-up of 14 months all five patients are alive. The two patients with lymphoma had their FDG avid lymph nodes easily identified and biopsied. In one patient with melanoma and one patient with suspected lymphoma, the preoperative scan revealed no FDG avid lesions. The PET probe confirmed this finding in the operating room. Clinical applications of PET probe guided surgery include restaging for previously treated lymphoma patients, localization and resection of metastatic FDG avid nodules especially in previously operated or radiated fields and biopsy of PET findings difficult to localize.
There are few clinical data on technical limitations and radiocolloid kinetics related to sentinel lymph node (SLN) biopsy for breast cancer.
In 70 clinical node-negative patients, unfiltered 99mTc ...sulfur-colloid was injected peritumorally and cutaneous hot spots were mapped with a gamma probe. SLN biopsy was performed followed by axillary lymph node dissection. Missed radioactive nodes (nodes not under hot spots) were removed from axillary lymph node dissection specimens and submitted separately.
At least one hot spot was mapped in 69 patients (98%) and SLNs were retrieved in 62 (89%). No radiolabeled nodes were found in five (7%) and only nodes not under hot spots were retrieved in three patients (4%). Residual nodes not under hot spots were retrieved in 17 patients (24%) in whom at least one SLN specimen had been found. Diffuse radioactivity around the radiocolloid injection site impeded identification of all radiolabeled nodes during SLN biopsy, and was responsible for one of two false negatives (20 node-positive patients; false-negative rate 10%). Hot spot radioactivity, number of radiolabeled nodes, and nodal radioactivity did not change with time interval from radiocolloid injection to surgery (0.75-6.25 hours).
Although SLN localization rate is high, intraparenchymal injection may predispose to failure of radiocolloid migration, failure to identify SLNs because of high radiation background, and false-negative outcomes. Alternative routes of radiocolloid administration should be explored.
Microhabitats of four terrestrial passerines were studied in an Atlantic forest remnant of southern Brazil, in two areas (northern and southern) of the Mata dos Godoy State Park (PG). Grallaria varia ...and Hylopezus nattereri showed low abundance and occurred in only one PG area, while Chamaeza campanisona and Corythopis delalandi were recorded in two. The microhabitats of C. campanisona, G. varia, and H. nattereri had many large trees and a dense understory. Corythopis delalandi was in areas having few large trees.
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