•Effect of laser remelting on mechanical properties under cyclic loading was studied.•Effect of laser remelting on wear volume and friction coefficient was studied.•Effect of laser remelting and heat ...treatment on Charpy impact energy was studied.•Anisotropy in hardness, residual stress, Charpy impact energy and wear was studied.•Reciprocating sliding tests with ball above and below configuration were conducted.
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The reliability and quality of additively manufactured parts are questionable. The present study aimed to improve the surface quality and mechanical and tribological properties of a Ti6Al4V alloy manufactured using selective laser melting (SLM). The effects of the laser remelting on its surface topology, mechanical properties, and sliding wear in a ball-on-plate configuration with a ball either above or below the plate were investigated systematically. The influence of the laser remelting approach on the anisotropy of the mechanical and tribological properties was compared with that of the heat treatment approach. The surface quality and high cycle fatigue strength improved with an increase in the number of melting steps. The compressive and impact strengths also increased with an increase in the number of melting steps. The wear resistance in both configurations was higher in the remelted samples than in the samples after SLM. The results confirmed that laser remelting, as an affordable approach, could significantly improve the reliability of parts fabricated by the SLM process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This volume examines the elements of formalism and decisionism in Russian legal thinking and, also, the impact of conservatism on the interplay of these elements. This combination leads to internal ...contradictions in theorizing about law and rights in Russian legal culture.
This study aimed to investigate the microstructure and tribological properties of the equiatomic AlCoCrFeNi high-entropy alloys (HEAs) fabricated using selective laser melting (SLM) and spark plasma ...sintering (SPS) processes. Sliding wear behavior in a ball-on-disk configuration with a ball either above or below the disk of the SLM and SPS samples was investigated. A detailed study of the effects of wear debris on the sliding wear behavior was undertaken to clarify the effect of wear debris entrapment in a wear scar. The wear volumes in the as-built SLM samples were slightly higher than in the SPS counterparts in both configurations. Wear volume and coefficient of friction values in the ball-above configuration were significantly lower than in the ball-below configuration. The present results indicated that the wear debris significantly influenced the mechanical contact properties of the HEA, providing new insight into the performance of the new materials in various conditions that could be considered to widen classical approaches by including the fate of the detached particles in the wear process. The impacts of wear debris on the design and application of these novel alloys should be considered.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The facilitated activity of N-methyl-D-aspartate receptors (NMDARs) in the central and peripheral nervous systems promotes neuropathic pain. Amitriptyline (ATL) and desipramine (DES) are tricyclic ...antidepressants (TCAs) whose anti-NMDAR properties contribute to their analgetic effects. At therapeutic concentrations <1 µM, these medicines inhibit NMDARs by enhancing their calcium-dependent desensitization (CDD). Li+, which suppresses the sodium−calcium exchanger (NCX) and enhances NMDAR CDD, also exhibits analgesia. Here, the effects of different Li+s on TCA inhibition of currents through native NMDARs in rat cortical neurons recorded by the patch-clamp technique were investigated. We demonstrated that the therapeutic Li+s of 0.5−1 mM cause an increase in ATL and DES IC50s of ~10 folds and ~4 folds, respectively, for the Ca2+-dependent NMDAR inhibition. The Ca2+-resistant component of NMDAR inhibition by TCAs, the open-channel block, was not affected by Li+. In agreement, clomipramine providing exclusively the NMDAR open-channel block is not sensitive to Li+. This Ca2+-dependent interplay between Li+, ATL, and DES could be determined by their competition for the same molecular target. Thus, submillimolar Li+s may weaken ATL and DES effects during combined therapy. The data suggest that Li+, ATL, and DES can enhance NMDAR CDD through NCX inhibition. This ability implies a drug−drug or ion−drug interaction when these medicines are used together therapeutically.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Advanced modern materials are required to operate at challenging conditions including mutual interactions under pressure and at elevated temperatures. In the present work, unidirectional sliding ...tests were performed to evaluate the wear behaviour of tribo-couple of AlCrN PVD coating deposited onto a stainless steel substrate and Si3N4, Al2O3, and ZrO2 ceramic balls counterbodies at different speeds ranged from as low as 0.002 up to as high as 1.458 m s−1 and temperatures from 20 up to 800 °C. The wear scars were studied with the help of 3D optical surface profilometry, scanning electron microscopy, energy-dispersive and Raman spectroscopy. Bulk and flash temperatures conditioned by sliding were analytically calculated. The wear mechanisms responsible for surface degradation are detailed.
•Testing of materials at high temperature in wide range of velocities is possible.•Test temperature and heat generated by sliding influencing failure of materials.•Maps illustrating performance of Si3N4-AlCrN tribocouple are prepared.•Al2O3 is the best (Si3N4-average; ZrO2-worst) for 800 °C with speed up to 1.4 ms-1.•AlCrN PVD coating is reliable for high temperature sliding wear applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The plasma membrane Na
/Ca
-exchanger (NCX) has recently been shown to regulate Ca
-dependent N-methyl-D-aspartate receptor (NMDAR) desensitization, suggesting a tight interaction of NCXs and NMDARs ...in lipid nanoclasters or "rafts". To evaluate possible role of this interaction we studied effects of Li
on NMDA-elicited whole-cell currents and Ca
responses of rat cortical neurons in vitro before and after cholesterol extraction by methyl-β-cyclodextrin (MβCD).
Substitution Li
for Na
in the external solution caused a concentration-dependent decrease of steady-state NMDAR currents from 440 ± 71 pA to 111 ± 29 pA in 140 mM Na
and 140 mM Li
, respectively. The Li
inhibition of NMDAR currents disappeared in the absence of Ca
in the external solution (Ca
-free), suggesting that Li
enhanced Ca
-dependent NMDAR desensitization. Whereas the cholesterol extraction with MβCD induced a decrease of NMDAR currents to 136 ± 32 pA in 140 mM Na
and 46 ± 15 pA in 140 mM Li
, the IC
values for the Li
inhibition were similar (about 44 mM Li
) before and after this procedure. In the Ca
-free Na
solution the steady-state NMDAR currents after the cholesterol extraction were 47 ± 6% of control values. Apparently this amplitude decrease was not Ca
-dependent. In the Na
solution containing 1 mM Ca
the Ca
-dependent NMDAR desensitization was greater when cholesterol was extracted. Obviously, this procedure promoted its development. In agreement, Li
and KB-R7943, an inhibitor of NCX, both considerably reduced NMDA-activated Ca
responses. The cholesterol extraction itself caused a decrease of NMDA-activated Ca
responses and, in addition, abolished the effects of Li
and KB-R7943. The cholesterol loading into the plasma membrane caused a recovery of the KB-R7943 effects.
Taken together our data suggest that NCXs downregulate the Ca
-dependent NMDAR desensitization. Most likely, this is determined by a tight functional interaction of NCX and NMDAR molecules because of their co-localization in membrane lipid rafts. The destruction of these rafts is accompanied by an enhancement of NMDAR desensitization and a loss of NCX-selective agent effects on NMDARs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
New impact-abrasion tests allowing one to evaluate performance of hardmetals operating in conditions of intensive abrasion, severe fatigue and high impact loads can be of great importance for many ...industrial applications. A new test for studying wear behaviour of hardmetals under high impact loads was developed and employed for evaluation of performance of different hardmetal grades in comparison with polycrystalline diamond (PCD). The wear behaviour of the same hardmetal grades and PCD was also examined in the standard ASTM B611 test, which was employed as a control. A significant difference between wear rates of near-nano and submicron hardmetals on the one hand and medium-coarse and ultra-coarse hardmetals on the other hand in the new impact-abrasion test was established. The wear of PCD in the impact-abrasion test was found to be close to zero. Examinations of wear surfaces of the tested hardmetal samples allowed wear mechanisms of the different hardmetal grades to be evaluated. The wear mechanism of the near-nano and submicron grades in the impact-abrasion test comprises phenomena of wear and flattening of WC grains, partial removal of Co from binder interlayers in a thin surface layer and formation of shallow holes on the worn surface as a result of detachment of relatively small WC-Co fragments. The wear mechanism of the medium-coarse and ultra-coarse grades in the impact-abrasion test includes phenomena of full removal of the binder phase from thick Co interlayers among WC grains leaving them unsupported. This leads to cracking, damage and breakage of the WC grains as well as detachment of large WC-Co fragments resulting in significantly higher wear rates of the medium-coarse and ultra-coarse grades in comparison with the near-nano and submicron grades.
•New test for studying impact-abrasive wear was developed.•Significant difference among wear rates of different hardmetals was found.•Wear mechanism of fine-grain grades comprises detachments of WC-Co fragments.•Coarse-grain grades are subjected to removal of Co interlayers among WC grains.•Wear mechanism of coarse-grain grades includes damage of WC grains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Tungsten heavy alloys (W-HA) behavior under powerful fusion related plasma streams were studied.•The use of Fe-Ni alloy as the binder phase has decreased the development of cracks.•The layer of ...decreased microhardness of W-HA is decreased in comparison to pure tungsten.
The morphological and structural changes of two different dual-phase tungsten alloy (either 3% or 5% of an added mixture of Fe and Ni) are investigated after deuterium plasma irradiation. Heat flux factor of deuterium plasma pulses is comparable to transient events in ITER. This study compares the changes in tungsten alloy materials between two different regimes with a different number of plasma pulses. Fe and Ni as a binder play an essential role in absorbing plasma shocks to decrease the morphological and structural changes. These results are compared to changes of pure single and double forged tungsten irradiated in similar conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
It is known that overexpression of
N
-methyl-D-aspartate receptors (NMDARs) contributes to central sensitization and development of neuropathic pain. Tricyclic antidepressants (TCAs), amitriptyline ...(ATL), and desipramine (DES) exhibit analgetic anti-NMDAR activity and are commonly utilized for pain therapy. This property is determined by their ability to enhance the calcium-dependent desensitization (CDD) of NMDARs. Coincidently ethanol and cholesterol, the ubiquitous food supplements, also modulate NMDAR CDD. The convergence of the effects of these compounds on a similar calcium-dependent process allows to assume their interaction on NMDARs. Since there is no information on whether ethanol supplementation and cholesterol deficit interfere with TCA inhibition of NMDARs at a cellular level, here we investigated this issue. Whole-cell NMDA-activated currents were recorded in rat cortical neurons of primary cultures to study how the IC
50
values for TCA inhibition of NMDARs are influenced by ethanol and cholesterol extraction from the plasma membrane with methyl-β-cyclodextrin. Ethanol at 0.03% did not reliably affect the steady-state NMDA-activated currents. At this threshold concentration ethanol, however, increased IC
50
s for ATL and DES abolishing their calcium-dependent inhibition of NMDARs but did not change IC
50
for clomipramine (CLO), which is calcium-independent. Whereas the ethanol effects on ATL-induced NMDAR inhibition reached a maximum at 2 mM external Ca
2+
, for DES the maximum was achieved already at 1 mM external Ca
2+
, that correlates with the manifestation of the calcium-dependent inhibition of NMDARs by these agents. Cholesterol depletion also increased IC
50
s for both ATL and DES abolishing the calcium-dependent inhibition of NMDARs. The restitution of cholesterol in the plasma membrane reversed the ATL IC
50
back to the low values, by a restoration of calcium-dependence of ATL. These observations are consistent with the explanation that either 0.03% ethanol or cholesterol extraction may interrupt some intermediate step of CDD transduction or augment NMDAR CDD to the maximal level so that ATL and DES could not further enhance CDD. It is likely that anti-NMDAR action of ATL and DES against neuropathic pain could demonstrate peculiarities in therapeutic profiles during cholesterol decline in aging or medical treatments and ethanol supplementations even in quantities that are insufficient to cause the symptoms of intoxication.
One of the most suitable renewable energy sources is geothermal energy (providing heating as well as electricity). In order to achieve a suitable depth of drilling (several kilometres), it is ...required to increase the wear resistance, durability and reliability of key components of the deep drills. The effect of abrasive powders on impact energy transmission and/or damping during wear of Polycrystalline Diamond (PCD) cutting elements was evaluated due to its highest resistance in abrasive conditions. The characteristic features of wear mechanism are presented and discussion is supported by SEM images and EDS maps. The strength of silica sand, quartzite, granite, basalt, marble, limestone, pumice is compared to the force transmitted through the contact zone, damping characteristics and stiffness of abrasive particles. It was found that the laboratory impact-abrasive device enables to initiate damage, characteristic for specific abrasive powder, imitating drilling of such mineral. The mechanism of wear of PCD elements in impact-abrasive conditions depends on the strength and shape of abrasive particles as well as on their behaviour during impact (impact energy damping). The wear of PCD elements in the impact-abrasive conditions was close to zero and their use in new generations of deep drills is expected.
•Proposed monitoring system allows tracking the process taking place in wear zone.•Adjustment of impact-abrasive wear conditions for testing of PCD is possible.•Damping, stiffness, strength characteristics of abrasives are discussed.•Characteristic features of PCD wear are found during laboratory test.•Possible mechanism for energy damping in wear zone is proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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