Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction

Using a discrete-lattice approach, we calculate the conductance spectra between a normal metal and an s-wave Larkin-Ovchinnikov (LO) superconductor, with the junction interface oriented {\em along} the direction of the order-parameter (OP) modulation. The OP sign reversal across one single nodal line can induce a sizable number of zero-energy Andreev bound states around the nodal line, and a hybridized midgap-states band is formed amid a momentum-dependent gap as a result of the periodic array of nodal lines in the LO state. This band-in-gap structure and its anisotropic properties give rise to distinctive features in both the point-contact and tunneling spectra as compared with the BCS and Fulde-Ferrell cases. These spectroscopic features can serve as distinguishing signatures of the LO state.Comment: 8 pages, 5 figures; version as publishe

Numerical study of spin quantum Hall transitions in superconductors with broken time-reversal symmetry

We present results of numerical studies of spin quantum Hall transitions in disordered superconductors, in which the pairing order parameter breaks time-reversal symmetry. We focus mainly on p-wave superconductors in which one of the spin components is conserved. The transport properties of the system are studied by numerically diagonalizing pairing Hamiltonians on a lattice, and by calculating the Chern and Thouless numbers of the quasiparticle states. We find that in the presence of disorder, (spin-)current carrying states exist only at discrete critical energies in the thermodynamic limit, and the spin-quantum Hall transition driven by an external Zeeman field has the same critical behavior as the usual integer quantum Hall transition of non-interacting electrons. These critical energies merge and disappear as disorder strength increases, in a manner similar to those in lattice models for integer quantum Hall transition.Comment: 9 pages, 9 figure

Silver Orthophosphate Immobilized on Flaky Layered Double Hydroxides as the Visible-Light-Driven Photocatalysts

Flaky layered double hydroxide (FLDH) was prepared by the reconstruction of its oxide in alkali solution. The composites with FLDH/Ag3PO4 mass ratios at 1.6 : 1 and 3 : 1 were fabricated by the coprecipitation method. The powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, and UV-vis diffuse reflectance spectroscopy. The results indicated that the well-distributed Ag3PO4 in a fine crystallite size was formed on the surface of FLDH. The photocatalytic activities of the Ag3PO4 immobilized on FLDH were significantly enhanced for the degradation of acid red G under visible light irradiation compared to bare Ag3PO4. The composite with the FLDH/Ag3PO4 mass ratio of 3 : 1 showed a higher photocatalytic efficiency

Conductance characteristics between a normal metal and a two-dimensional Fulde-Ferrell-Larkin-Ovchinnikov superconductor: the Fulde-Ferrell state

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state has received renewed interest recently due to the experimental indication of its presence in CeCoIn$_5$, a quasi 2-dimensional (2D) d-wave superconductor. However direct evidence of the spatial variation of the superconducting order parameter, which is the hallmark of the FFLO state, does not yet exist. In this work we explore the possibility of detecting the phase structure of the order parameter directly using conductance spectroscopy through micro-constrictions, which probes the phase sensitive surface Andreev bound states of d-wave superconductors. We employ the Blonder-Tinkham-Klapwijk formalism to calculate the conductance characteristics between a normal metal (N) and a 2D $s$- or $d_{x^2-y^2}$-wave superconductor in the Fulde-Ferrell state, for all barrier parameter $z$ from the point contact limit ($z=0$) to the tunneling limit ($z \gg 1$). We find that the zero-bias conductance peak due to these surface Andreev bound states observed in the uniform d-wave superconductor is split and shifted in the Fulde-Ferrell state. We also clarify what weighted bulk density of states is measured by the conductance in the limit of large $z$.Comment: 10 pages, 13 figure

Fulde-Ferrell-Larkin-Ovchinnikov state in disordered s-wave superconductors

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a superconducting state stabilized by a large Zeeman splitting between up- and down-spin electrons in a singlet superconductor. In the absence of disorder, the superconducting order parameter has a periodic spatial structure, with periodicity determined by the Zeeman splitting. Using the Bogoliubov-de Gennes (BdG) approach, we investigate the spatial profiles of the order parameters of FFLO states in a two-dimensional s-wave superconductors with nonmagnetic impurities. The FFLO state is found to survive under moderate disorder strength, and the order parameter structure remains approximately periodic. The actual structure of the order parameter depends on not only the Zeeman field, but also the disorder strength and in particular the specific disorder configuration.Comment: 9 pages, 6 figures; minor change to text and added references; version as publishe

Loss of MYO5B expression deregulates late endosome size which hinders mitotic spindle orientation

Recycling endosomes regulate plasma membrane recycling. Recently, recycling endosome-associated proteins have been implicated in the positioning and orientation of the mitotic spindle and cytokinesis. Loss of MYO5B, encoding the recycling endosome-associated myosin Vb, is associated with tumor development and tissue architecture defects in the gastrointestinal tract. Whether loss of MYO5B expression affects mitosis is not known. Here, we demonstrate that loss of MYO5B expression delayed cytokinesis, perturbed mitotic spindle orientation, led to the misorientation of the plane of cell division during the course of mitosis, and resulted in the delamination of epithelial cells. Remarkably, the effects on spindle orientation, but not cytokinesis, were a direct consequence of physical hindrance by giant late endosomes, which were formed in a chloride channel-sensitive manner concomitant with a redistribution of chloride channels from the cell periphery to late endosomes upon loss of MYO5B. Rab7 availability was identified as a limiting factor for the development of giant late endosomes. In accordance, increasing rab7 availability corrected mitotic spindle misorientation and cell delamination in cells lacking MYO5B expression. In conclusion, we identified a novel role for MYO5B in the regulation of late endosome size control and identify the inability to control late endosome size as an unexpected novel mechanism underlying defects in cell division orientation and epithelial architecture. Loss of the recycling endosome-associated motor protein myosin Vb causes the formation of giant late endo-lysosomes; these in turn hinder the orientation of the mitotic spindle and chromosome segregation. Deregulated endosome size thus hampers faithful cell division

Activated mouse CD4+Foxp3−CD4^+Foxp3^− T cells facilitate melanoma metastasis via Qa-1-dependent suppression of NK-cell cytotoxicity

The regulatory activities of mouse $CD^4+Foxp3^+$ T cells on various immune cells, including NK cells, have been well documented. Under some conditions, conventional $CD4^+Foxp3^−$ T cells in the periphery are able to acquire inhibitory function on other T cells, but their roles in controlling innate immune cells are poorly defined. As a potential cellular therapy for cancer, ex vivo activated $CD4^+Foxp3^−$ effector T cells are often infused back in vivo to suppress tumor growth and metastasis. Whether such activated T cells could affect NK-cell control of tumorigenesis is unclear. In the present study, we found that mitogen-activated $CD4^+Foxp3^−$ T cells exhibited potent suppressor function on NK-cell proliferation and cytotoxicity in vitro, and notably facilitated B16 melanoma metastasis in vivo. Suppression of NK cells by activated $CD4^+Foxp3^−$ T cells is cell-cell contact dependent and is mediated by Qa-1:NKG2A interaction, as administration of antibodies blocking either Qa-1 or NKG2A could completely reverse this suppression, and significantly inhibited otherwise facilitated melanoma metastasis. Moreover, activated $CD4^+Foxp3^−$ cells from Qa-1 knockout mice completely lost the suppressor activity on NK cells, and failed to facilitate melanoma metastasis when transferred in vivo. Taken together, our findings indicate that innate anti-tumor response is counter regulated by the activation of adaptive immunity, a phenomenon we term as “activation-induced inhibition”. Thus, the regulatory role of activated $CD4^+Foxp3^−$ T cells in NK-cell activity must be taken into consideration in the future design of cancer therapies

Safety evaluation of employing temporal interference transcranial alternating current stimulation in human studies

Temporal interference transcranial alternating current stimulation (TI-tACS) is a new technique of noninvasive brain stimulation. Previous studies have shown the effectiveness of TI-tACS in stimulating brain areas in a selective manner. However, its safety in modulating human brain neurons is still untested. In this study, 38 healthy adults were recruited to undergo a series of neurological and neuropsychological measurements regarding safety concerns before and after active (2 mA, 20/70 Hz, 30 min) or sham (0 mA, 0 Hz, 30 min) TI-tACS. The neurological and neuropsychological measurements included electroencephalography (EEG), serum neuron-specific enolase (NSE), the Montreal Cognitive Assessment (MoCA), the Purdue Pegboard Test (PPT), an abbreviated version of the California Computerized Assessment Package (A-CalCAP), a revised version of the Visual Analog Mood Scale (VAMS-R), a self-assessment scale (SAS), and a questionnaire about adverse effects (AEs). We found no significant difference between the measurements of the active and sham TI-tACS groups. Meanwhile, no serious or intolerable adverse effects were reported or observed in the active stimulation group of 19 participants. These results support that TI-tACS is safe and tolerable in terms of neurological and neuropsychological functions and adverse effects for use in human brain stimulation studies under typical transcranial electric stimulation (TES) conditions (2 mA, 20/70 Hz, 30 min)

Smart Mega-City Development in Practice: A Case of Shanghai, China

As Shanghai is a megacity and pioneer in smart city development in China, this paper used Shanghai as a megacity example to investigate smart city development over the past ten years. By collecting data from multiple sources, a case study methodology was utilized to explore Shanghai’s smart megacity development in practice. Based on the key events and phases of Shanghai’s smart city development, the practical contents were systematically investigated. The main conclusions of this research included four aspects, consisting of information infrastructure, information technology and industrial development, information perception and smart applications, and a security assurance system. Moreover, a conceptual framework for Shanghai’s smart city development was constructed by integrating the phases and contents. Furthermore, the implications of Shanghai’s smart city development are critically discussed and identified from five aspects, including the development pathway, the government’s role, the financing channel, information and communication technology (ICT)-driven development, and a people-oriented concept. This study benefits academia, governments, and practitioners by providing useful insights and valuable implications for other cities to develop smart cities