A model of rotating hotspots for 3:2 frequency ratio of HFQPOs in black hole X-ray binaries

We propose a model to explain a puzzling 3:2 frequency ratio of high frequency quasi-periodic oscillations (HFQPOs) in black hole (BH) X-ray binaries, GRO J1655-40, GRS 1915+105 and XTE J1550-564. In our model a non-axisymmetric magnetic coupling (MC) of a rotating black hole (BH) with its surrounding accretion disc coexists with the Blandford-Znajek (BZ) process. The upper frequency is fitted by a rotating hotspot near the inner edge of the disc, which is produced by the energy transferred from the BH to the disc, and the lower frequency is fitted by another rotating hotspot somewhere away from the inner edge of the disc, which arises from the screw instability of the magnetic field on the disc. It turns out that the 3:2 frequency ratio of HFQPOs in these X-ray binaries could be well fitted to the observational data with a much narrower range of the BH spin. In addition, the spectral properties of HFQPOs are discussed. The correlation of HFQPOs with jets from microquasars is contained naturally in our model.Comment: 8 pages, 4 figures. accepted by MNRA

Comparisons of stomatal parameters between normal and abnormal leaf of Bougainvillea spectabilis Willd

In this study, stomatal density (SD), stomatal index (SI), epidermal cell density (ED), guard cell length (GCL) and guard cell width (GCW) of normal and abnormal leaf of Bougainvillea spectabilis Willd were studied. This can be useful for further research of physical mechanism of abnormal leaf. Epidermal cells were polygonal with straight anticlinal walls in the adaxial epidermis of normal leaf; while in the abaxial epidermis of normal leaf, the epidermal cells were irregular with repand anticlinal walls. The stomata were anomocytic on normal leaf. No stomata were found in the adaxial epidermis of abnormal leaf. In abaxial epidermis of abnormal leaf, the epidermal cells were repand or sinuous. The stomata were anomocytic on abnormal leaf. The guard cells were kidney-shaped on normal and abnormal leaf. SD and SI of normal leaf were significantly higher than that of abnormal leaf. ED and GCL of abnormal leaf were higher than that of normal leaf in relative leaves length 37.5 and 50%. At other four stages, ED and GCL of abnormal leaf were smaller than that of normal leaf. SD, SI and ED had a negative correlation with relative leaf length; a significant positive correlation was observed between GCL and relative leaf length.Key words: Bougainvillea spectabilis Willd, normal leaf, abnormal leaf, stomatal density, epidermal cell density, stomatal index

How does interchange affect passengers' route choices in urban rail transit? - a case study of the Shanghai Metro

Interchange provides more flexibility in route choice, a key travel behaviour in urban rail transit, but its influence is usually simplified. This paper investigates how interchange affects route choice with passenger perception considered. At single-interchange level, perceived interchange time was proposed and modelled under three resolutions to capture passenger perception and its sensitivity. At route level, the influence of interchange was modeled by first comparing eight quantifications of interchange. Mixed logit models with the best interchange proxy were further developed to address the correlation among alternative routes and reveal the potential taste variations among passengers. Results based on Shanghai Metro data showed perceived interchange time, including passenger perception and interchange environment, better represents the influence of interchange in route choice, meanwhile the weights of interchanges on one route rise sequentially and non-linearly. The results can improve route choice prediction in demand modelling and route recommendation in advanced traveller information systems

Momentum Distribution of Near-Zero-Energy Photoelectrons in the Strong-Field Tunneling Ionization in the Long Wavelength Limit

We investigate the ionization dynamics of Argon atoms irradiated by an ultrashort intense laser of a wavelength up to 3100 nm, addressing the momentum distribution of the photoelectrons with near-zero-energy. We find a surprising accumulation in the momentum distribution corresponding to meV energy and a \textquotedblleft V"-like structure at the slightly larger transverse momenta. Semiclassical simulations indicate the crucial role of the Coulomb attraction between the escaping electron and the remaining ion at extremely large distance. Tracing back classical trajectories, we find the tunneling electrons born in a certain window of the field phase and transverse velocity are responsible for the striking accumulation. Our theoretical results are consistent with recent meV-resolved high-precision measurements.Comment: 5 pages, 4 figure

Precision spectroscopy and density-dependent frequency shifts in ultracold Sr

By varying the density of an ultracold $^{88}$Sr sample from $10^9$ cm$^{-3}$ to $> 10^{12}$ cm$^{-3}$, we make the first definitive measurement of the density-related frequency shift and linewidth broadening of the $^1S_0$ - $^3P_1$ optical clock transition in an alkaline earth system. In addition, we report the most accurate measurement to date of the $^{88}$Sr $^1S_0 - ^3P_1$ optical clock transition frequency. Including a detailed analysis of systematic errors, the frequency is ($434 829 121 312 334 \pm 20_{stat} \pm 33_{sys}$) Hz.Comment: 4 pages, 4 figures, 1 table. submitte