507 research outputs found
Robust paramagnetism in Bi2-xMxRu2O7 (M=Mn,Fe,Co,Ni,Cu) pyrochlore
We report physical property characterization of Bi2-xMxRu2O7 pyrochlores,
including magnetic suseptibility, resistivity, and Seebeck coefficients. The
solid solution exists up to x=0.5 for (M=Cu,Ni,Co) and up to x=0.1 for
(M=Fe,Mn). None of the doped materials exhibit ferromagnetism or any localized
ruthenium moment behavior. Instead we find the Ru-O and Bi-O sublattices to be
essentially independent, with any magnetism resulting from the unpaired
transition metal dopant spins. Cobalt substitution for bismuth results in
localized Co{2+}, and low temperature spin-glass transitions in several cases.
Nickel moments on the pyrochlore lattice display properties intermediate to
localized and itinerant. Finally, copper doping results in only an enhancement
of the Pauli metallic density of states.Comment: submitted, Phys. Rev.
Study on the Failure Mechanism of the Polymorphic Mixture for Remanifactured Machinery Parts
The polymorphic mixture failure mode for multiple heterogeneity of remanifactured (RM) machinery parts makes it difficult to assess their lifetime. The Weibull distribution failure model of RM parts (substrate, coating layer, bonding surface and sudden failure) is constructed with failure time statistics of the parts in service, the latter is used to characterize the failure patterns of RM parts. In view of the multiple heterogeneity of RM parts, the Kaplan–Meier type decoupling method is used to analyze four sets of failure statistics, and each state of the Weibull failure function of the above parts is solved. It reveals the in-service failure mechanism of polymorphic mixtures for multiple heterogeneity of RM machinery parts. The validity and feasibility of the model are verified by the case study. Research results provide the theoretical basis for the design and preparation of a RM alloy powder and the improvement of RM technology. Moreover, the method for lifetime prediction and failure time evaluation of RM parts is proposed and validatedХарактер разрушения полиморфной смеси в условиях множественной гетерогенности модифицированных деталей затрудняет оценку срока службы оборудования. Модель разрушения распределения Вейбулла (разрушение подложки, наружного слоя, поверхости сцепления, мгновенное разрушение) построена на основании статистических данных о времени разрушения детелей в условиях эксплуатации. Использован метод разделения Каплана Мейера для анализа четырех множеств статистик разрушения, выполнено решение каждого состояния функции Вейбулла, что позволило установить механизм разрушения полиморфных смесей в условиях эксплуатации при множественной гетерогенности модифицированных деталей оборудования. На примере выполнения моделирования верифицированы достоверность и применимость модели. Создана теоретическая основа для разработки и изготовления порошка сплава и совершенствования технологии модифицирования. Разработан метод прогнозирования срока службы и оценки периода разрушения модифицированных деталей
Guiding and confining fast electrons by transient electric and magnetic fields with a plasma inverse cone
Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 16(2), 020702, 2009 and may be found at http://dx.doi.org/10.1063/1.307592
A substitution-dependent light-up fluorescence probe for selectively detecting Fe3+ ions and its cell imaging application
Deliberate design of specific and sensitive molecular probes with distinctive physical/chemical properties for analyte sensing is of great significance. Herein, by taking advantage of the position-dependent substituent effects, an aggregation-induced emission featured iron (III) probe from ortho-substituted pyridinyl-functionalized tetraphenylethylene (TPE-o-Py) is synthesized. It displays high sensitivity and selectivity toward iron (III) detection. The recognition arises from the position isomer of ortho-substitution, and the fact that TPE-o-Py has a low acid dissociation constant (pKa) that is close to that of hydrolyzed Fe3+. Importantly, TPE-o-Py as a light-up fluorescence probe could be employed for Fe3+sensing in living cells with a pronounced red-shift in fluorescence emission
The role of SIRT6 protein in aging and reprogramming of human induced pluripotent stem cells
Aging is known to be the single most important risk factor for multiple diseases. Sirtuin 6, or SIRT6, has recently been identified as a critical regulator of transcription, genome stability, telomere integrity, DNA repair, and metabolic homeostasis. A knockout mouse model of SIRT6 has displayed dramatic phenotypes of accelerated aging. In keeping with its role in aging, we demonstrated that human dermal fibroblasts (HDFs) from older human subjects were more resistant to reprogramming by classic Yamanaka factors than those from younger human subjects, but the addition of SIRT6 during reprogramming improved such efficiency in older HDFs substantially. Despite the importance of SIRT6, little is known about the molecular mechanism of its regulation. We show, for the first, time posttranscriptional regulation of SIRT6 by miR-766 and inverse correlation in the expression of this microRNA in HDFs from different age groups. Our results suggest that SIRT6 regulates miR-766 transcription via a feedback regulatory loop, which has implications for the modulation of SIRT6 expression in reprogramming of aging cells
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
Optical properties of MgH2 measured in situ in a novel gas cell for ellipsometry/spectrophotometry
The dielectric properties of alpha-MgH2 are investigated in the photon energy
range between 1 and 6.5 eV. For this purpose, a novel sample configuration and
experimental setup are developed that allow both optical transmission and
ellipsometric measurements of a transparent thin film in equilibrium with
hydrogen. We show that alpha-MgH2 is a transparent, colour neutral insulator
with a band gap of 5.6 +/- 0.1 eV. It has an intrinsic transparency of about
80% over the whole visible spectrum. The dielectric function found in this work
confirms very recent band structure calculations using the GW approximation by
Alford and Chou [J.A. Alford and M.Y. Chou (unpublished)]. As Pd is used as a
cap layer we report also the optical properties of PdHx thin films.Comment: REVTeX4, 15 pages, 12 figures, 5 table
Inclusive Charmonium Production via Double in Annihilation
Motivated by the recent observation of double charm quark pair production by
the Belle Collaboration, we calculate the complete
inclusive production cross sections for , , and
(J=0, 1, 2) plus in annihilation through a
virtual photon. We consider both color-singlet and color-octet contributions,
and give the analytical expressions for these cross sections. The complete
color-singlet calculations are compared with the approximate fragmentation
calculations as functions of the center-of-mass energy . We find that
most of the fragmentation results substantially overestimate the cross sections
(e.g. by a factor of 4 for and ) at the Belle and
BaBar energy GeV. The fragmentation results become a good
approximation only when is higher than about 100GeV. We further
calculate the color-octet contributions to these cross sections with analytical
expressions. We find that while the color-octet contribution to
inclusive production via double charm is negligible (only about 3%), the
color-octet contributions to and can be significant.Comment: 23 pages, 9 figures; color-octet contributions to the double charm
inclusive production of J/psi and chi_{cJ} (J=0,1,2) are added; references
are added; No change for the color-singlet par
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