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The observation of second-order nonlinear Hall effect generally requires broken inversion symmetry and other spatial symmetries (such as out-of-plane C2 symmetry) rather than time-reversal symmetry for the conventional Hall effect, which brings fascinating opportunities for the fundamental investigation and innovative concepts for device applications. However, the imposed symmetry constraints severely limit the accessibility of the second-order nonlinear Hall effect in many materials. Here, we report the observation of the second-order nonlinear Hall effect in bulk Td-WTe2 with symmetry constraints under the application of direct current (DC). The observed second-order nonlinear Hall effect is strongly dependent on the external DC with its magnitude being vanished at zero driving DC and linearly increased with increasing driving DC. Furthermore, the driving DC induced second-order nonlinear Hall effect in bulk Td-WTe2 exhibits the same twofold rotational symmetry as that of the intrinsic third-order nonlinear Hall effect, which is distinct from the second-order nonlinear Hall effect in few-layer Td-WTe2. In addition, similar driving DC induced second-order nonlinear features are also observed in the longitudinal direction. These imply that the driving DC induced second-order nonlinear transport properties may share the same physical origins as that of the intrinsic third-order nonlinear transport. Scaling relationship analyses further demonstrate that extrinsic scattering-related mechanism plays a dominant role in the observed high-order nonlinear transport properties. Our work outlines a potential roadmap to control the second-order nonlinear Hall effect in materials where crystal symmetry forbids this effect with both fundamental research interest and technological device applications. [ABSTRACT FROM AUTHOR]

In chemoradiation therapy, the synergy between the radiation and the chemotherapeutic agent (CA) can result in a super-additive treatment. A priori, this increased effectiveness could be estimated from model calculations, if absolute cross sections (ACSs) involved in cellular damage are substantially higher, when the CA binds to DNA. We measure ACSs for damages induced by 10 eV electrons, when DNA binds to the CA cisplatin as in chemotherapy. At this energy, DNA is damaged essentially by the decay of core-excited transient anions into bond-breaking channels. Films of cisplatin-DNA complexes of ratio 5:1 with thicknesses 10, 15, and 20 nm were irradiated in vacuum during 5–30 s. Conformation changes were quantified by electrophoresis and yields extrapolated from exposure-response curves. Base damages (BDs) were revealed and quantified by enzymatic treatment. The ACSs were generated from these yields by two mathematical models. For 3197 base-pair plasmid DNA, ACS for single strand breaks, double strand breaks (DSBs), crosslinks, non-DSB cluster damages, and total BDs is 71 ± 2, 9.3 ± 0.4, 10.1 ± 0.3, 8.2 ± 0.3, and 115 ± 2 ×10−15 cm2, respectively. These ACSs are higher than those of nonmodified DNA by factors of 1.6 ± 0.1, 2.2 ± 0.1, 1.3 ± 0.1, 1.3 ± 0.3, and 2.1 ± 0.4, respectively. Since LEEs are produced in large quantities by radiolysis and strongly interact with biomolecules, we expect such enhancements to produce substantial additional damages in the DNA of the nucleus of cancer cells during concomitant chemoradiation therapy. The increase damage appears sufficiently large to justify more elaborate simulations, which could provide a quantitative evaluation of molecular sensitization by Pt-CAs. [ABSTRACT FROM AUTHOR]

Understanding the occurrence of charge density wave (CDW) states in quasi-one-dimensional (quasi-1D) transition metal trichalcogenides has attracted substantial research interest. Here, we report the systematic control of hysteretic transitions in quasi-1D TiS3 microribbons by changing the thickness and the cooling rate. Two distinguished resistance hysteresis loops are observed at a high temperature of ∼290 K and a low temperature of ∼60 K, respectively. In addition, two hysteretic transitions exhibit different behaviors under the external perturbations, in which the high temperature hysteretic transition is sensitive to TiS3 microribbons thickness, while the low temperature hysteretic transition is probably related to the CDW state and is robust against external perturbations. Our findings will offer a new frontier of exploration of the hysteretic transitions in the quasi-1D transition metal trichalcogenides. [ABSTRACT FROM AUTHOR]

Superconducting proximity effect in the heterostructures opens up access to engineer superconductivity at the interface, and has inspired substantial research interest in the past decade. Here, we fabricate the van der Waals 2H-TaS2/NbSe2 heterostructure through the mechanical exfoliation and dry transfer technique. Enhanced superconductivity in 2H-TaS2 flakes with increased superconducting transition temperature by about 0.8 K is observed. Such enhancement is believed to be related to the leakage of the Cooper pairs from NbSe2 flakes to 2H-TaS2 flakes. In addition, the critical current of the superconducting transition of NbSe2 flakes is also increased in the heterostructures, which is related to the strengthened pairing strength of Cooper pairs in NbSe2 flakes arising from the interfacial coupling between NbSe2 flakes and 2H-TaS2 flakes. Our findings will open perspectives for insight into the superconducting proximity effect in the van der Waals heterostructures. [ABSTRACT FROM AUTHOR]

Diffuse correlation spectroscopy (DCS) is a well-established method that measures rapid changes in scattered coherent light to identify blood flow and functional dynamics within a tissue. While its sensitivity to minute scatterer displacements leads to a number of unique advantages, conventional DCS systems become photon-limited when attempting to probe deep into the tissue, which leads to long measurement windows (∽1 sec). Here, we present a high-sensitivity DCS system with 1024 parallel detection channels integrated within a single-photon avalanche diode array and demonstrate the ability to detect mm-scale perturbations up to 1 cm deep within a tissue-like phantom at up to a 33 Hz sampling rate. We also show that this highly parallelized strategy can measure the human pulse at high fidelity and detect behaviorally induced physiological variations from above the human prefrontal cortex. By greatly improving the detection sensitivity and speed, highly parallelized DCS opens up new experiments for high-speed biological signal measurement. [ABSTRACT FROM AUTHOR]

Structured illumination microscopy (SIM) achieves doubled spatial resolution through exciting the specimen with high-contrast, high-frequency sinusoidal patterns. Such an illumination pattern can be generated by laser interference or incoherent structured patterns. Opto-electronic devices, such as a Spatial Light Modulator (SLM) or a Digital Micro-mirror Device (DMD), can provide rapid switch of illumination patterns for SIM. Although the DMD is much more cost-effective than the SLM, it was previously restricted in association with incoherent light sources, as its diffractive orders are related to the incident angle and the wavelength of coherent incidence. To extend its application with coherent illumination, here, we model the DMD as a blazed grating and simulate the effect with DMD pattern changes in the SIM. With careful analysis of the illumination contrast along different angles and phases, we report a fast, high-resolution, and cost-efficient SIM with DMD modulation. Our home-built laser interference-based DMD-SIM (LiDMD-SIM) reveals the nuclear pore complex and microtubule in mammalian cells with doubled spatial resolution. We further proposed the multi-color LiDMD-SIM concept by jointly employing the DMD ON/OFF states with different incident angles for different wavelengths, with high contrast and maximum resolution enhancement. [ABSTRACT FROM AUTHOR]

Presents an improved feedback control technique for the direct current (dc) electrochemical fabrication of scanning tunneling microscopy microtips. Use of the etching current as the only control signal; Electrochemical etching process; Differential feedback control method.

The observation of second-order nonlinear Hall effect generally requires broken inversion symmetry and other spatial symmetries (such as out-of-plane C2 symmetry) rather than time-reversal symmetry for the conventional Hall effect, which brings fascinating opportunities for the fundamental investigation and innovative concepts for device applications. However, the imposed symmetry constraints severely limit the accessibility of the second-order nonlinear Hall effect in many materials. Here, we report the observation of the second-order nonlinear Hall effect in bulk Td-WTe2 with symmetry constraints under the application of direct current (DC). The observed second-order nonlinear Hall effect is strongly dependent on the external DC with its magnitude being vanished at zero driving DC and linearly increased with increasing driving DC. Furthermore, the driving DC induced second-order nonlinear Hall effect in bulk Td-WTe2 exhibits the same twofold rotational symmetry as that of the intrinsic third-order nonlinear Hall effect, which is distinct from the second-order nonlinear Hall effect in few-layer Td-WTe2. In addition, similar driving DC induced second-order nonlinear features are also observed in the longitudinal direction. These imply that the driving DC induced second-order nonlinear transport properties may share the same physical origins as that of the intrinsic third-order nonlinear transport. Scaling relationship analyses further demonstrate that extrinsic scattering-related mechanism plays a dominant role in the observed high-order nonlinear transport properties. Our work outlines a potential roadmap to control the second-order nonlinear Hall effect in materials where crystal symmetry forbids this effect with both fundamental research interest and technological device applications. [ABSTRACT FROM AUTHOR]

We report the experimental observation of the quasi-whispering-gallery mode (quasi-WGM) polariton lasing in a one dimensional ZnO microrod cavity at room temperature. Under nonresonant optical pulsed excitation, we measure the pumping power dependence of the emission intensity and the blueshift of the polariton modes, and a fairly low lasing threshold for the quasi-WG mode is determined. We also measure the lasing threshold versus the photon-exciton detuning by dispersion simulations. These experiment results show that both of the WGMs with higher Q factors and the quasi-WGMs with lower Q factors can lase when the detuning between the optical modes and the exciton energies is optimum. [ABSTRACT FROM AUTHOR]