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We aimed to estimate the effects of indoor and outdoor temperature on wintertime blood pressure (BP) among peri-urban Beijing adults.We enrolled 1279 adults (ages: 40-89 years) and conducted measurements in two winter campaigns in 2018-2019 and 2019-2020. Study staff traveled to participant homes to administer a questionnaire and measure brachial and central BP. Indoor temperature was measured in the 5 min prior to BP measurement. Outdoor temperature was estimated from regional meteorological stations. We used multivariable mixed-effects regression models to estimate the within-individual and between-individual effects of indoor and outdoor temperatures on BP.Indoor and outdoor temperatures ranged from 0.0 to 28 °C and -14.3 to 6.4 °C, respectively. In adjusted models, a 1 °C increase in indoor temperature was associated with decreased SBP [-0.4 mmHg, 95% confidence interval (CI): -0.7 to -0.1 (between-individual; brachial and central BP); -0.5 mmHg, 95% CI: -0.8 to -0.2 (within-individual, brachial BP); -0.4 mmHg, 95% CI: -0.7 to -0.2 (within-individual, central BP)], DBP [-0.2 mmHg, 95% CI:-0.4 to -0.03 (between-individual); -0.3 mmHg, 95% CI: -0.5 to -0.04 (within-individual)], and within-individual pulse pressure [-0.2 mmHg, 95% CI: -0.4 to -0.04 (central); -0.3 mmHg, 95% CI: -0.4 to -0.1 (brachial)]. Between-individual SBP estimates were larger among participants with hypertension. There was no evidence of an effect of outdoor temperature on BP.Our results support previous findings of inverse associations between indoor temperature and BP but contrast with prior evidence of an inverse relationship with outdoor temperature. Wintertime home heating may be a population-wide intervention strategy for high BP and cardiovascular disease in China.

Metals are canonical plasmonic media at infrared and optical wavelengths, allowing one to guide and manipulate light at the nanoscale. A special form of optical waveguiding is afforded by highly anisotropic crystals revealing the opposite signs of the dielectric functions along orthogonal directions. These media are classified as hyperbolic and include crystalline insulators, semiconductors, and artificial metamaterials. Layered anisotropic metals are also anticipated to support hyperbolic waveguiding. However, this behavior remains elusive, primarily because interband losses arrest the propagation of infrared modes. Here, we report on the observation of propagating hyperbolic waves in a prototypical layered nodal-line semimetal ZrSiSe. The observed waveguiding originates from polaritonic hybridization between near-infrared light and nodal-line plasmons. Unique nodal electronic structures simultaneously suppress interband loss and boost the plasmonic response, ultimately enabling the propagation of infrared modes through the bulk of the crystal.

We visualized negative refraction of phonon polaritons, which occurs at the interface between two natural crystals. The polaritons—hybrids of infrared photons and lattice vibrations—form collimated rays that display negative refraction when passing through a planar interface between the two hyperbolic van der Waals materials: molybdenum oxide (MoO 3 ) and isotopically pure hexagonal boron nitride (h 11 BN). At a special frequency ω 0 , these rays can circulate along closed diamond-shaped trajectories. We have shown that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps that result from polaritonic-level repulsion and strong coupling.

We investigate transient nanotextured heterogeneity in vanadium dioxide (VO

Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe2, prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the optical constants following femtosecond photoexcitation. By monitoring the phase velocity of the waveguide modes, we detect incoherent A-exciton bleaching along with a coherent optical Stark shift in WSe2., The authors use time-resolved scanning near-field optical microscopy to probe the ultrafast excitonic processes and their impact on waveguide operation in transition metal dichalcogenide crystals. They observe significant modulation of the complex index by monitoring waveguide modes on the fs time scale, and identify both coherent and incoherent manipulations of WSe2 excitonic resonances.

As a type of fermions without counterpart in high energy physics, triply degenerate fermions show exotic physical properties, which are represented by triply degenerate nodal points in topological semimetals. Here, based on the space group theory analysis, we propose a practical guidance for seeking a topological semimetal with triply degenerate nodal points located at a symmetric axis, which is applicable to both symmorphic and nonsymmorphic crystals. By using this guidance in combination with the first-principles electronic structure calculations, we predict a class of triply degenerate topological semimetals $R{\mathrm{Rh}}_{6}{\mathrm{Ge}}_{4}\phantom{\rule{4pt}{0ex}}(R=\text{Y},\text{La},\text{Lu})$. In these compounds, the triply degenerate nodal points are located at the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}A$ axis and not far from the Fermi level. Especially, ${\mathrm{LaRh}}_{6}{\mathrm{Ge}}_{4}$ has a pair of triply degenerate nodal points located at just $\ensuremath{\sim}3$ meV below the Fermi level. Considering the fact that the single crystals of $R{\mathrm{Rh}}_{6}{\mathrm{Ge}}_{4}$ have been synthesized experimentally, the $R{\mathrm{Rh}}_{6}{\mathrm{Ge}}_{4}$ class of compounds will be an appropriate platform for studying exotic physical properties of triply degenerate topological semimetals.

Twisting a route for surface plasmons Graphene is an atomically thin material that supports highly confined plasmon polaritons, or nano-light, with very low loss. The properties of graphene can be made richer by introducing and then rotating a second layer so that there is a slight angle between the atomic registry. Sunku et al. show that the moiré patterns that result from such twisted bilayer graphene also provide confined conducting channels that can be used for the directed propagation of surface plasmons. Controlling the structure thereby provides a pathway to control and route surface plasmons for a nanophotonic platform. Science , this issue p. 1153

here is increasing recognition today that professional musicians aren't the only ones vulnerable to performance-related injuries and high levels of stress. College-age music students and even students in middle and high school are experiencing many of the same types of overuse syndromes and similar levels of performance anxiety. Indeed, many aspects of musical activities are probably more stressful for a student than they are for an accomplished professional. Students may find practicing more taxing mentally and emotionally than professional musicians do. The mastery of complex skills takes years of hard work, requiring patience and a capacity for delayed gratification. Lessons and rehearsals mean hearing a lot of criticism. And then, performing may carry more emotional challenge for students who have not yet fully consolidated their technique or developed the kind of confidence in their abilities that professional musicians rely on. We should be concerned about the longterm effects of elevated stress in students.

Infrared spectroscopy of VO${}_{2}$ thin films at high spatial resolution shows new electronic and lattice states due to epitaxial strain that differ fundamentally from those in the bulk. This is the first ultra-broadband infrared near-field study of a correlated electron material, made possible by the newly developed synchrotron infrared near-field spectroscopy method (SINS) on the Advanced Light Source at Lawrence Berkeley National Laboratory.

We use low energy optical spectroscopy and first principles LDA+DMFT calculations to test the hypothesis that the anomalous transport properties of strongly correlated metals originate in the strong temperature dependence of their underlying resilient quasiparticles. We express the resistivity in terms of an effective plasma frequency $\omega_p^*$ and an effective scattering rate $ 1/\tau^*_{tr}$. We show that in the archetypal correlated material V2O3, $\omega_p^*$ increases with increasing temperature, while the plasma frequency from partial sum rule exhibits the opposite trend . $ 1/\tau^*_{tr}$ has a more pronounced temperature dependence than the scattering rate obtained from the extended Drude analysis. The theoretical calculations of these quantities are in quantitative agreement with experiment. We conjecture that these are robust properties of all strongly correlated metals, and test it by carrying out a similar analysis on thin film NdNiO3 on LaAlO3 substrate., Comment: 6 pages, 5 figures including appendix

If one studies the physics of free electron lasers (FELs) with finite-length electron pulses, one finds that the physics is quite different at the ends of the pulse from that in the center of the pulse. At the tail end of the pulse, the radiation is always moving forward relative to the electrons, and therefore the radiation fields do not build up sufficiently to cause saturation. This effect has been called “superradiant” since the power scales as the square of the current, I 2 , rather than I 4 3 as in normal FEL theory [R. Bonifacio and F. Casagrande, Nucl. Instr. and Meth. A239 (1985) 36]. In this article a computer code is used that performs a true Fourier transform of the beam current and advances all radiation frequencies according to the correct phase velocity. This code can model an FEL correctly even if the radiation group velocity becomes equal to or less than the electron velocity. The physics of the superradiant FEL interaction is studied as a function of “cooperation length”, where this length is defined as the distance traveled by the radiation pulse relative to the electron pulse during transit of the wiggler.

For an electron moving in an undulating magnetic field, there are two frequencies of radiation that can produce a resonance. There is a forward wave which corresponds to the free electron laser (FEL) resonance and there is also a backward wave. In the electron frame of reference these two resonances are identical except for the direction of the Poynting vector of the radiation. In the lab frame, however, the frequency of the forward wave appears upshifted and the frequency of the backward wave seems downshifted. Because of the correspondence between the two resonances, the backward wave can be used to stimulate incoherent emission of radiation at the frequency of the forward wave. A scheme is proposed for the utilization of the correspondence of these resonances. A backward wave at near twice the undulator wavelength can be used to produce incoherent radiation at the frequency of the forward resonance, which for sufficiently energetic electron beams could be in the XUV spectral region. The process could be used to enhance the radiation power over self-amplified spontaneous emission in single-pass XUV FELs. Some computer simulations are performed to estimate the amount of enhancement possible.

We demonstrate an electrolyte-based voltage tunable vanadium dioxide (VO2) memory metasurface. Large spatial scale, low voltage, non-volatile switching of terahertz (THz) metasurface resonances is achieved through voltage application using an ionic gel to drive the insulator-to-metal transition in an underlying VO2 layer. Positive and negative voltage application can selectively tune the metasurface resonance into the “off” or “on” state by pushing the VO2 into a more conductive or insulating regime respectively. Compared to graphene based control devices, the relatively long saturation time of resonance modification in VO2 based devices suggests that this voltage-induced switching originates primarily from electrochemical effects related to oxygen migration across the electrolyte–VO2 interface.

Epitaxial strain can play an important role in controlling the local phase dynamics of transition metal oxides. With scattering-type scanning near-field optical microscopy, we visualize the three dimensional landscape of phase inhomogeneity in strained VO2 films grown on [100]R TiO2 substrates. We demonstrate that three different symmetries are spontaneously broken in the vicinity of the VO2 phase transition: (1) Monoclinic-tetragonal (rutile) crystal symmetry breaking due to the structural phase transition, (2) in-plane (x-y plane) rotational symmetry breaking due to the formation of periodic strain domains, and (3) out-of-plane (z-axis) mirror symmetry breaking at the film cross-section due to substrate-induced epitaxial strain.

Motivated by its use in a two-beam accelerator, we have studied a “steady-state” FEL; i.e., a periodic but very long structure in which the electron beam energy is replenished once a period with a short induction acceleration unit. We have studied longitudinal particle motion in such a device using a 1-D simulation code. We show that after an initial startup section, particle detrapping from the pondermotive wave is minimal in a steady-state FEL of several kilometers. A simple linear model of particle diffusion is shown to describe the numerical results quite well.

In this paper the author derives a Green's function for an FEL in a waveguide. The radiation field is decomposed into transverse waveguide modes and an integral is derived for the evolution of each mode. The treatment is exact; there is no slowly varying envelope approximation and no averaging over an undulator period. Each transverse mode consists of a spectrum of longitudinal frequencies that obey the waveguide dispersion relation ω 2 c 2 = γ 1 2 + k 2 , where γ1 depends on the transverse mode. The waveguide confines the radiation to propagation in a single dimension. This reduces a 3-D electromagnetic problem to a 1-D problem. The integral formulation of a waveguide FEL will be applied to studying frequency sidebands in FELs. It should also be particularly useful in studying slippage effects in FELs with short electron bunches.

Analysis of the rf phase in the FEL section of a two beam accelerator using a many particle simulation has been done. The simulation was based upon equations describing the FEL in the resonant particle approximation. The main emphasis of the analysis is on the evolution of the radiation−amplitude and phase of the FEL electrons. (AIP)

Recently, renewed interest in an FEL version of a two‐beam accelerator (TBA) has prompted a study of practical system and structure designs for achieving the specified physics goals. This paper presents elements of a realistic design for an FEL/TBA suitable for a 1 TeV, 17 GHz linear collider.