2,637 research outputs found
Observation of Andreev bound states in bicrystal grain-boundary Josephson junctions of the electron doped superconductor LaCeCuO
We observe a zero-bias conductance peak (ZBCP) in the ab-plane quasiparticle
tunneling spectra of thin film grain-boundary Josephson junctions made of the
electron doped cuprate superconductor LaCeCuO. An applied magnetic field
reduces the spectral weight around zero energy and shifts it non-linearly to
higher energies consistent with a Doppler shift of the Andreev bound states
(ABS) energy. For all magnetic fields the ZBCP appears simultaneously with the
onset of superconductivity. These observations strongly suggest that the ZBCP
results from the formation of ABS at the junction interfaces, and,
consequently, that there is a sign change in the symmetry of the
superconducting order parameter of this compound consistent with a d-wave
symmetry.Comment: 9 pages, 7 figures; December 2004, accepted for publication in Phys.
Rev.
Evidence for a quantum phase transition in the electron-doped cuprate Pr2-xCexCuO4+d from Hall and resistivity measurements
The doping and temperature dependence of the Hall coefficient, RH, and
ab-plane resistivity in the normal state down to 350mK is reported for oriented
films of the electron-doped high-Tc superconductor Pr2-xCexCuO4+d. The doping
dependence of b (r=r0+AT^b) and R_sub_H (at 350 mK) suggest a quantum phase
transition at a critical doping near x=0.165.Comment: 11 pages 4 figures Phys. Rev. Lett. 92, 167001 (2004
Differential expression of basement membrane collagen-IV alpha l to alpha 6 chains during oral carcinogenes
This study aimed to resolve if basement membrane (BM) collagen alpha chains undergo remodeling during oral. carcinogenesis. Using immunohistochemistry and transmission electron microscopy, we found that BMs in oral epithelial dysplasias (OED: mild, n=10; moderate, n=10; severe, n=10) and carcinoma in situ (CIS) (n=10) differed from normal mucosa (n=6) and oral epithelial hyperplasia (n=5) in showing: (1) excessive lamina densa-like material ultrastructurally, and (2) stronger immunoexpression for alpha 5(IV) than for alpha 1(IV), alpha 2(IV), and alpha 6(IV) chains-findings that implicate these molecules' role as an adhesive template for the attachment and persistence of basal dysplastic cells. Incipient loss of BM integrity in CIS, where alpha 5(IV)/alpha 6(IV) chains were more frequently absent than alpha 1(IV)/alpha 2(IV) chains, suggests that alpha(IV) network disruption is crucial for progression of dysplastic cells into the extracellular compartment, marking transition into the invasive phase. In carcinomatous BM, the disappearance of alpha(IV) chains was more severe in poorly differentiated oral squamous cell carcinoma (OSCC) (n=10) than in well-differentiated OSCC (n=10). In all samples examined, alpha 3(IV) and alpha 4(IV) chains were absent. These findings taken together suggest that BM collagen-IV alpha chains undergo remodeling where selective increase and loss of these molecules are probably early and late events, respectively, during progression of oral dysplasia to cancer. This record was migrated from the OpenDepot repository service in June, 2017 before shutting down
The relationship between chaotic behavior and tunneling effect in quantum transport devices(1)Current topics of quantum chaos in nanosciences, Chaos and Nonlinear Dynamics in Quantum-Mechanical and Macroscopic Systems)
この論文は国立情報学研究所の電子図書館事業により電子化されました。狭い金属ゲート(QPC)を両端に有する開放型量子ドットについて、零磁場近傍の磁気抵抗のピーク形状が、ゲート電圧を変化させることによってローレンツ型とカスプ型が交互に現れる現象が観測された。このローレンツ型とカスプ型が交互に現れる要因としては、QPCによるトンネリング効果と量子ドットによる弱局在の両方が関係しているものではないかと推測され、考察を行った。We have studied transport properties in the low-temperature magnetoresistance through the ballistic narrow path restricted by short width metallic gates, which cause a quantum point contact(QPC) which have a saddle point potential, on the 2 dimensional electron gas(2DEG) system. An alternate and systematic variation between a Lorentzian line fitting and a cusplike line fitting in the zero-field peaks has been observed, as sweeping the gate voltage. It indicates a possibility of existence of chaotic and regular paths on the short gated ballistic/tunneling transport. We will discuss on the quantum chaos behavior on the systematic variation between the Lorentzian and the cusp-like peakshape based on the disordered path system under the short gate, and suggest a relation with level repulsion of energy spectrum
Evidence for a Nodeless Gap from the Superfluid Density of Optimally Doped Pr_{1.855}Ce_{0.145}CuO_{4-y} Films
We present measurements of the ab-plane magnetic penetration depth,
\lambda(T), in five optimally doped Pr_{1.855}Ce_{0.145}CuO_{4-y} films for 1.6
K \leq T \leq T_c \sim 24 K. Low resistivities, high superfluid densities
n_s(T)\propto \lambda^{-2}(T), high T_c's, and small transition widths are
reproducible and indicative of excellent film quality. For all five films,
\lambda^{-2}(T)/\lambda^{-2}(0) at low T is well fitted by an exponential
temperature dependence with a gap, \Delta_{min}, of 0.85 k_B T_c. This behavior
is consistent with a nodeless gap and is incompatible with d-wave
superconductivity.Comment: 5 pages, 4 figures, reorganized for clarit
In situ proliferation and differentiation of macrophages in dental pulp
The presence of macrophages in dental pulp is well known. However, whether these macrophages proliferate and differentiate in the dental pulp in situ, or whether they constantly migrate from the blood stream into the dental pulp remains unknown. We have examined and compared the development of dental pulp macrophages in an organ culture system with in vivo tooth organs to clarify the developmental mechanism of these macrophages. The first mandibular molar tooth organs from ICR mice aged between 16 days of gestation (E16) to 5 days postnatally were used for in vivo experiments. Those from E16 were cultured for up to 14 days with or without 10% fetal bovine serum. Dental pulp tissues were analyzed with immunohistochemistry to detect the macrophages and with reverse transcription and the polymerase chain reaction (RT-PCR) for the detection of factors related to macrophage development. The growth curves for the in vivo and in vitro cultured cells revealed similar numbers of F4/80-positive macrophages in the dental pulp. RT-PCR analysis indicated the constant expression of myeloid colony-stimulating factor (M-CSF) in both in-vivo- and in-vitro-cultured dental pulp tissues. Anti-M-CSF antibodies significantly inhibited the increase in the number of macrophages in the dental pulp. These results suggest that (1) most of the dental pulp macrophages proliferate and differentiate in the dental pulp without a supply of precursor cells from the blood stream, (2) M-CSF might be a candidate molecule for dental pulp macrophage development, and (3) serum factors might not directly affect the development of macrophages
Theory on quench-induced pattern formation: Application to the isotropic to smectic-A phase transitions
During catastrophic processes of environmental variations of a thermodynamic
system, such as rapid temperature decreasing, many novel and complex patterns
often form.
To understand such phenomena, a general mechanism is proposed based on the
competition between heat transfer and conversion of heat to other energy forms.
We apply it to the smectic-A filament growth process during quench-induced
isotropic to smectic-A phase transition. Analytical forms for the buckling
patterns are derived and we find good agreement with experimental observation
[Phys. Rev. {\bf E55} (1997) 1655]. The present work strongly indicates that
rapid cooling will lead to structural transitions in the smectic-A filament at
the molecular level to optimize heat conversion. The force associated with this
pattern formation process is estimated to be in the order of
piconewton.Comment: 9 pages in RevTex form, with 3 postscript figures. Accepted by PR
Observation of the first gravitational microlensing event in a sparse stellar field : the Tago event
We report the observation of the first gravitational microlensing event in a
sparse stellar field, involving the brightest (V=11.4 mag) andclosest (~ 1 kpc)
source star to date. This event was discovered by an amateurastronomer, A.
Tago, on 2006 October 31 as a transient brightening, by ~4.5 mag during a ~15
day period, of a normal A-type star (GSC 3656-1328) in the Cassiopeia
constellation. Analysis of both spectroscopic observations and the light curve
indicates that this event was caused by gravitational microlensing rather than
an intrinsically variable star. Discovery of this single event over a 30 year
period is roughly consistent with the expected microlensing rate for the whole
sky down to V = 12 mag stars. However, the probability for finding events with
such a high magnification (~ 50) is much smaller, by a factor ~1/50, which
implies that the true event rate may be higher than expected. This discovery
indicates the potential of all sky variability surveys, employing frequent
sampling by telescopes with small apertures and wide fields of view, for
finding such rare transient events, and using the observations to explore
galactic disk structure and search for exo-planets.Comment: 13 pages, 2 tables, 3 figures, accepted by Ap
Possible pseudogap behavior of electron doped high-temperature superconductors
We have measured the low-energy quasiparticle excitation spectrum of the
electron doped high-temperature superconductors (HTS) Nd(1.85)Ce(0.15)CuO(4-y)
and Pr(1.85)Ce(0.15)CuO(4-y) as a function of temperature and applied magnetic
field using tunneling spectroscopy. At zero magnetic field, for these optimum
doped samples no excitation gap is observed in the tunneling spectra above the
transition temperature Tc. In contrast, below Tc for applied magnetic fields
well above the resistively determined upper critical field, a clear excitation
gap at the Fermi level is found which is comparable to the superconducting
energy gap below Tc. Possible interpretations of this observation are the
existence of a normal state pseudogap in the electron doped HTS or the
existence of a spatially non-uniform superconducting state.Comment: 4 pages, 4 ps-figures included, to be published in Phys. Rev. B,
Rapid Com
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