1,828 research outputs found
Muon anomalous magnetic moment due to the brane-stretching effect
We investigate the contribution of extra dimensions to the muon anomalous
magnetic moment by using an ADD-type 6-dimensional model. This approach
analyzes the extent of the influence of classical brane fluctuations on the
magnetic moment. When we consider that the brane fluctuations are static in
time, they add new potential terms to the Schr{\"o}dinger equation through the
induced vierbein. This paper shows that the brane fluctuation is responsible
for the brane-stretching effect. This effect would be capable of reproducing
the appropriate order for recent Brookhaven National Laboratory measurements of
the muon (g-2) deviation.Comment: 17 pages, 1 figure, minor changed, accepted for Phys. Rev.
Novel Orbital Ordering induced by Anisotropic Stress in a Manganite Thin Film
We performed resonant and nonresonant x-ray diffraction studies of a
Nd0.5Sr0.5MnO3 thin film that exhibits a clear first-order transition. Lattice
parameters vary drastically at the metal-insulator transition at 170K (=T_MI),
and superlattice reflections appear below 140K (=T_CO). The electronic
structure between T_MI and T_CO is identified as A-type antiferromagnetic with
the d_{x2-y2} ferroorbital ordering. Below T_CO, a new type of antiferroorbital
ordering emerges. The accommodation of the large lattice distortion at the
first-order phase transition and the appearance of the novel orbital ordering
are brought about by the anisotropy in the substrate, a new parameter for the
phase control.Comment: 4pages, 4figure
Crystallographic and superconducting properties of the fully-gapped noncentrosymmetric 5d-electron superconductors CaMSi3 (M=Ir, Pt)
We report crystallographic, specific heat, transport, and magnetic properties
of the recently discovered noncentrosymmetric 5d-electron superconductors
CaIrSi3 (Tc = 3.6 K) and CaPtSi3 (Tc = 2.3 K). The specific heat suggests that
these superconductors are fully gapped. The upper critical fields are less than
1 T, consistent with limitation by conventional orbital depairing. High,
non-Pauli-limited {\mu}0 Hc2 values, often taken as a key signature of novel
noncentrosymmetric physics, are not observed in these materials because the
high carrier masses required to suppress orbital depairing and reveal the
violated Pauli limit are not present.Comment: 8 pages, 8 figure
Imaging Oxygen Defects and their Motion at a Manganite Surface
Manganites are technologically important materials, used widely as solid
oxide fuel cell cathodes: they have also been shown to exhibit
electroresistance. Oxygen bulk diffusion and surface exchange processes are
critical for catalytic action, and numerous studies of manganites have linked
electroresistance to electrochemical oxygen migration. Direct imaging of
individual oxygen defects is needed to underpin understanding of these
important processes. It is not currently possible to collect the required
images in the bulk, but scanning tunnelling microscopy could provide such data
for surfaces. Here we show the first atomic resolution images of oxygen defects
at a manganite surface. Our experiments also reveal defect dynamics, including
oxygen adatom migration, vacancy-adatom recombination and adatom bistability.
Beyond providing an experimental basis for testing models describing the
microscopics of oxygen migration at transition metal oxide interfaces, our work
resolves the long-standing puzzle of why scanning tunnelling microscopy is more
challenging for layered manganites than for cuprates.Comment: 7 figure
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HRB-22 preirradiation thermal analysis
This report describes the preirradiation thermal analysis of the HRB-22 capsule designed for irradiation in the removable beryllium (RB) position of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). CACA-2 a heavy isotope and fission product concentration calculational code for experimental irradiation capsules was used to determine time dependent fission power for the fuel compacts. The Heat Engineering and Transfer in Nine Geometries (HEATING) computer code, version 7.2, was used to solve the steady-state heat conduction problem. The diameters of the graphite fuel body that contains the compacts and the primary pressure vessel were selected such that the requirements of running the compacts at an average temperature of < 1,250 C and not exceeding a maximum fuel temperature of 1,350 C was met throughout the four cycles of irradiation
Magnetic Ground State of PrLaCeCuO with Varied Oxygen Depletion Probed by Muon Spin Relaxation
The magnetic ground state of an electron-doped cuprate superconductor
PrLaCeCuO () has been
studied by means of muon spin rotation/relaxation (\msr) over a wide variety of
oxygen depletion, . Appearance of weak random magnetism
over entire crystal volume has been revealed by a slow exponential relaxation.
The absence of -dependence for the random magnetism and the multiplet
pattern of muon Knight shift at higher fields strongly suggest that the random
moments are associated with excited Pr ions under crystal electric
field.Comment: 6 pages, 4 figures, submitted to J. Phys. Soc. Jp
Parvalbumin interneuron dysfunction in a thalamo-prefrontal cortical circuit in Disc1 locus impairment mice
Altered cortical excitation-inhibition (E-I) balance resulting from abnormal parvalbumin interneuron (PV IN) function is a proposed pathophysiological mechanism of schizophrenia (SZ) and other major psychiatric disorders. Preclinical studies have indicated that disrupted-in-schizophrenia-1 (DISC1) is a useful molecular lead to address the biology of prefrontal cortex dependent cognition and PV IN function. To date, prefrontal cortical inhibitory circuit function has not been investigated in depth in Disc1 locus impairment (LI) mouse models. Therefore, we used a Disc1 LI mouse model to investigate E-I balance in medial prefrontal cortical (mPFC) circuits. We found that inhibition onto layer 3 excitatory pyramidal neurons in the mPFC was significantly reduced in Disc1 LI mice. This reduced inhibition was accompanied by decreased GABA release from local PV, but not somatostatin (SOM) interneurons, and by impaired feedforward inhibition in the mediodorsal thalamus (MD) to mPFC circuit. Our mechanistic findings of abnormal PV IN function in a Disc1 LI model provide insight into biology that may be relevant to neuropsychiatric disorders including schizophrenia.SIGNIFICANCE STATEMENT A popular theory suggests that dysregulation of fast-spiking parvalbumin interneurons (PV INs) and elevated excitation-inhibition (E-I) balance contribute to the pathophysiology of various psychiatric disorders. Previous studies suggest that genetic perturbations of the disrupted-in-schizophrenia-1 (Disc1) gene affect prefrontal cortex-dependent cognition and PV IN function, but synaptic and circuit physiology data are lacking. Here, we provide evidence that the presynaptic function of PV INs in the medial prefrontal cortex is altered in Disc1 LI mice and that E-I balance is elevated within a thalamofrontal circuit known to be important for cognition. These findings may contribute to our understanding of the biology that gives rise to cognitive symptoms in a range of neuropsychiatric disorders
Synchrotron Radiation XRD Analysis of Indialite in Y-82094 Ungrouped Carbonaceous Chondrite
Y-82094 is an ungrouped type 3.2 carbonaceous chondrite, with abundant chondrules making 78 vol.% of the rock. Among these chondrules, an unusual porphyritic Al-rich magnesian chondrule is reported that consists of a cordierite-like phase, Al-rich orthopyroxene, cristobalite, and spinel surrounded by an anorthitic mesostasis. The reported chemical formula of the cordierite-like phase is Na(0.19)Mg(1.95)Fe(0.02)Al(3.66)Si(5.19)O18, which is close to stoichiometric cordierite (Mg2Al3[AlSi5O18]). Although cordierite can be present in Al-rich chondrules, it has a high temperature polymorph (indialite) and it is therefore necessary to determine whether it is cordierite or indialite in order to better constrain its formation conditions. In this abstract we report on our synchrotron radiation X-ray diffraction (SR-XRD) study of the cordierite-like phase in Y-82094
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