Relation between numerical model and vibration: behavior diagnosis for bucket wheel drive assembly at the bucket wheel excavator

A drive assembly of bucket wheel at the bucket-wheel excavator (BWE), as a rule, is a unit characterized by large force having huge torque and mass with structures in different arrangement including the support structures as well. Behavior prediction is of crucial importance in order to apply the right approach of operation and maintenance on gearbox, electrical engine as well for structural elements supporting this assembly. It is obvious that vibrations measured at distinctive points of the entire drive assembly and support structure represent the main prediction parameter. The measurement results are used to confirm mathematical model developed by means of finite element method, which is based on theory on flexibility, static and dynamical review for obtained result

X Chromosome Inactivation and Differentiation Occur Readily in ES Cells Doubly-Deficient for MacroH2A1 and MacroH2A2

Macrohistones (mH2As) are unusual histone variants found exclusively in vertebrate chromatin. In mice, the H2afy gene encodes two splice variants, mH2A1.1 and mH2A1.2 and a second gene, H2afy2, encodes an additional mH2A2 protein. Both mH2A isoforms have been found enriched on the inactive X chromosome (Xi) in differentiated mammalian female cells, and are incorporated into the chromatin of developmentally-regulated genes. To investigate the functional significance of mH2A isoforms for X chromosome inactivation (XCI), we produced male and female embryonic stem cell (ESC) lines with stably-integrated shRNA constructs that simultaneously target both mH2A1 and mH2A2. Surprisingly, we find that female ESCs deficient for both mH2A1 and mH2A2 readily execute and maintain XCI upon differentiation. Furthermore, male and female mH2A-deficient ESCs proliferate normally under pluripotency culture conditions, and respond to several standard differentiation procedures efficiently. Our results show that XCI can readily proceed with substantially reduced total mH2A content

Normal Human Pluripotent Stem Cell Lines Exhibit Pervasive Mosaic Aneuploidy

Human pluripotent stem cell (hPSC) lines have been considered to be homogeneously euploid. Here we report that normal hPSC – including induced pluripotent - lines are karyotypic mosaics of euploid cells intermixed with many cells showing non-clonal aneuploidies as identified by chromosome counting, spectral karyotyping (SKY) and fluorescent in situ hybridization (FISH) of interphase/non-mitotic cells. This mosaic aneuploidy resembles that observed in progenitor cells of the developing brain and preimplantation embryos, suggesting that it is a normal, rather than pathological, feature of stem cell lines. The karyotypic heterogeneity generated by mosaic aneuploidy may contribute to the reported functional and phenotypic heterogeneity of hPSCs lines, as well as their therapeutic efficacy and safety following transplantation

Koszty utraconej produkcji wywołane uszkodzeniem gumowej taśmy transportowej w układzie maszynowym do zdejmowania nadkładu

In this paper the average malfunction costs (lost production) of the overburden excavation system on the Tamnava - East field open-pit mine caused by the failure of belt conveyor rubber belts which work on the bucket wheel excavator, belt wagon and spreader are determined, i.e. the unit cost of system malfunction per hour of belt conveyor work during belt lifetime. The basis for the calculation of malfunction costs is presented by the proposed methodology for the analysis of rubber belt working time to failure based on the fact that working time until sudden failure (tear, breakthrough) can be described by exponential distribution while working time until gradual failure can be described by normal distribution. The proposed methodology as well as the expression for malfunction cost determination can be used, with appropriate adoptions, in the analysis of the functioning of other open-pit mines for better planning of malfunctions, requirements for spare rubber belts as well reductions in working costs, i.e. they can indicate better (optimal) maintenance strategy.W prezentowanym artykule wyznaczono średnie koszty awarii (utraconej produkcji) układu maszynowego do zdejmowania nadkładu, wykorzystywanego w kopalni odkrywkowej Tamnava - East field, spowodowanej uszkodzeniem przenośnikowych taśm gumowych zastosowanych w koparce wielonaczyniowej, samobieżnym przenośniku taśmowym oraz zwałowarce. Koszt zdefiniowano jako jednostkowy koszt awarii układu na godzinę pracy przenośnika taśmowego podczas cyklu życia taśmy. Podstawę obliczeń kosztów awarii stanowiła zaproponowana metoda analizy czasu pracy taśmy gumowej do uszkodzenia, oparta na fakcie, iż czas pracy do nagłego uszkodzenia (rozerwanie, przebicie) można opisać za pomocą rozkładu wykładniczego, natomiast czas pracy do stopniowego uszkodzenia - za pomocą rozkładu normalnego. Proponowana metodologia, jak również równania do wyznaczania kosztów awarii mogą być wykorzystywane, przy odpowiedniej adaptacji, do analizy funkcjonowania innych kopalni odkrywkowych służąc lepszemu planowaniu awarii, zapotrzebowania na zapasowe pasy gumowe oraz redukcji kosztów pracy. Mogą one, innymi słowy, wskazywać (optymalną) strategię utrzymania ruchu