Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer Part II- Experimental Results

In this paper is presented a preceding procedure that should be conducted in order to successfully regenerate damaged forging dies by the hard facing process. After the tool damage types identification, as well as their causes, we have chosen the procedure and the parameters of hard facing that we further corrected by conducting the test hard facings on models. Thus, we were able to relate the experimental results outputs with the repair technology, taking as a criterion the quality of the surface layers wear resistance such as friction coefficient and width of hard faced zone, hardness and its distribution in cross section, then microstructure of characteristic of hard faced zones, etc. This research points out significancy of tribological properties of certain types of carbides and their effects on metal matrix, in which carbides are embedded. Our tribological investigations have shown that the working life of the hard faced tool can be longer than that of the new tool

Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer - Part I - Theoretical Considerations

This paper gives a theoretical review of influence of the most important alloying elements on steel, and review of the most important carbide-forming elements and states the conditions which elements should fulfill in order to be considered as carbide-forming. It primarily involves alloying elements which in the iron-carbon system can form simple, complex or special carbides, i.e. phases of interstitial and substitutive type. It also gives a review of carbide types that are formed during either production or reparatory hard facing of steel parts with different types of filler materials

In vivo imaging reveals reduced activity of neuronal circuits in a mouse tauopathy model

Pathological alterations of tau protein play a significant role in the emergence and progression of neurodegenerative disorders. Tauopathies are characterized by detachment of the tau protein from neuronal microtubules, and its subsequent aberrant hyperphosphorylation, aggregation and cellular distribution. The exact nature of tau protein species causing neuronal malfunction and degeneration is still unknown. In the present study, we used mice transgenic for human tau with the frontotemporal dementia with parkinsonism-associated P301S mutation. These mice are prone to develop fibrillar tau inclusions, especially in the spinal cord and brainstem. At the same time, cortical neurons are not as strongly affected by fibrillar tau forms, but rather by soluble tau forms. We took advantage of the possibility to induce formation of neurofibrillary tangles in a subset of these cortical neurons by local injection of preformed synthetic tau fibrils. By using chronic in vivo two-photon calcium imaging in awake mice, we were able for the first time to follow the activity of individual tangle-bearing neurons and compare it to the activity of tangle-free neurons over the disease course. Our results revealed strong reduction of calcium transient frequency in layer 2/3 cortical neurons of P301S mice, independent of neurofibrillary tangle presence. These results clearly point to the impairing role of soluble, mutated tau protein species present in the majority of the neurons investigated in this study

DEVELOPMENT AND OPTIMIZATION OF CARVEDILOL FORMULATION USING EXPERIMENTAL DESIGN

The aim of this paper was to develop and optimize the carvedilol tablets formulation using the full factorial design. The content of binder (PVP K30), content of disintegrant (crospovidone) and main compression force were used as the independent variables. Tablets were prepared by wet granulation. The percentage of released carvedilol from prepared formulation after 10 minutes was defined as the response. It has been found that formulation with the low content of binding agents (4.8%), high content of disintegrant (4.5%) and compression force of 50 N has the best profile of drug. The optimal formulation was defined based on implementation of pharmaceuticaltechnological tests (testing strength, friability, disintegrating, contents of drug substance, drug release profiles). The stability of the optimal formulation with carvedilol was estimated using the aging tests

Kinematic magnetic resonance imaging study of the brain stem and cervical cord by dynamic neck motion

Background: The aim was to examine the position of the brain stem and cervical cord following the neck flexion and extension. Materials and methods: The serial sagittal T2-weighted magnetic resonance imaging (MRI) sections of the cervical cord and brain stem were made in 6 volunteers. The images were mainly used to measure certain distances and angles of the brain stem and cervical cord in the neutral position, and then following the head and neck flexion and extension. Results: The measurements showed that the pons is slightly closer to the clivus following the neck flexion; the medulla oblongata is somewhat distant to the basion but closer to the odontoid process. At the same time, the spino-medullary angle diminishes in size. On the other hand, the upper cervical cord slightly approaches the posterior wall of the spinal canal, the lower cervical cord is closer to the anterior wall, while the angle between them is significantly larger in size. After the cervical cord extension, the rostral pons is somewhat distant to the clivus, whereas the caudal pons and the medulla are slightly closer to the clivus and the basion. At the same time, the spino-medullary angle diminishes in size. The cervical cord is mainly closer to the posterior wall of the spinal canal, whilst its angle is significantly smaller. Conclusions: The obtained results regarding the brain stem and cervical cord motion can be useful in the kinetic MRI examination of certain congenital disorders, degenerative diseases, and traumatic injuries of the craniovertebral junction and the cervical spine

Electron-impact excitation of the (5s(2)5p) P-2(1/2) -> (5s(2)6s) S-2(1/2) transition in indium: Theory and experiment

We present angle-integrated and angle-differential cross sections for electron-impact excitation of the (5s(2)5p) P-2(1/2) -> (5s(2)6s) S-2(1/2) transition in atomic indium. Experimental data for six incident electron energies between 10 and 100 eV are compared with predictions from semirelativistic and fully relativistic B-spline R-matrix calculations, as well as a fully relativistic convergent close-coupling model. Agreement between our measured and calculated data is, with a few exceptions, found to be typically very good. Additionally, the agreement between the present theoretical predictions is generally excellent, with the remaining small deviations being associated with the slightly different, although still very accurate, descriptions of the target structure. Agreement between the present results and an earlier relativistic distorted-wave computation [T. Das, R. Srivastava, and A. D. Stauffer, Phys. Lett. A 375, 568 (2011)] was, however, found to be marginal, particularly at 10 and 20 eV