A novel predictor of unsustained return of spontaneous circulation in cardiac arrest patients through a combination of capnography and pulse oximetry: a multicenter observational study

BACKGROUND:Unsustained return of spontaneous circulation(ROSC)is a critical barrier to survival in cardiac arrest patients.This study examined whether end-tidal carbon dioxide(ETCO_(2))and pulse oximetry photoplethysmogram(POP)parameters can be used to identify unsustained ROSC.METHODS:We conducted a multicenter observational prospective cohort study of consecutive patients with cardiac arrest from 2013 to 2014.Patients’general information,ETCO_(2),and POP parameters were collected and statistically analyzed.RESULTS:The included 105 ROSC episodes(from 80 cardiac arrest patients)comprised 51 sustained ROSC episodes and 54 unsustained ROSC episodes.The 24-hour survival rate was significantly higher in the sustained ROSC group than in the unsustained ROSC group(29.2%vs.9.4%,P<0.05).The logistic regression analysis showed that the difference between after and before ROSC in ETCO_(2)(ΔETCO_(2))and the difference between after and before ROCS in area under the curve of POP(ΔAUCp)were independently associated with sustained ROSC(odds ratio[OR]=0.931,95%confi dence interval[95%CI]0.881-0.984,P=0.011 and OR=0.998,95%CI 0.997-0.999,P<0.001).The area under the receiver operating characteristic curve ofΔETCO_(2),ΔAUCp,and the combination of both to predict unsustained ROSC were 0.752(95%CI 0.660-0.844),0.883(95%CI 0.818-0.948),and 0.902(95%CI 0.842-0.962),respectively.CONCLUSION:Patients with unsustained ROSC have a poor prognosis.The combination ofΔETCO_(2) andΔAUCp showed signifi cant predictive value for unsustained ROSC.

Acoustic Bilayer Gradient Metasurfaces for Perfect and Asymmetric Beam Splitting

We experimentally and theoretically present a paradigm for the accurate bilayer design of gradient metasurfaces for wave beam manipulation,producing an extremely asymmetric splitting effect by simply tailoring the interlayer size.This concept arises from anomalous diffraction in phase gradient metasurfaces and the precise combination of the phase gradient in bilayer metasurfaces.Ensured by different diffraction routes in momentum space for incident beams from opposite directions,extremely asymmetric acoustic beam splitting can be generated in a robust way,as demonstrated in experiments through a designed bilayer system.Our work provides a novel approach and feasible platform for designing tunable devices to control wave propagation.

Phase-Gradient Metasurfaces Based on Local Fabry–Perot Resonances

In this work,we present a new mechanism for designing phase-gradient metasurfaces(PGMs)to control an electromagnetic wavefront with high efficiency.Specifically,we design a transmission-type PGM,formed by a periodic subwavelength metallic slit array filled with identical dielectrics of different heights.It is found that when Fabry-Perot(FP)resonances occur locally inside the dielectric regions,in addition to the common phenomenon of complete transmission,the transmitted phase differences between two adjacent slits are exactly the same,being a nonzero constant.These local FP resonances ensure total phase shift across a supercell,fully covering a range of 0 to 2π,satisfying the design requirements of PGMs.Further research reveals that,due to local FP resonances,there is a one-to-one correspondence between the phase difference and the permittivity of the filled dielectric.A similar approach can be extended to the reflection-type case and other wavefront transformations,creating new opportunities for wave manipulation.

Programmable heating and quenching for non-equilibrium thermochemical synthesis

Conventional thermochemical syntheses by continuous heating under near equilibrium conditions face critical challenges in improving the synthesis rate,selectivity,catalyst stability and energy efficiency,owing to the lack of temporal control over the reaction temperature and time,and thus the reaction pathways.As an alternative,Dong with authors from the University of Maryland,University of Delaware,Princeton University,Johns Hopkins University,and Peking University recently presented a non-equilibrium,continuous synthesis technique that uses pulsed heating and quenching(for example,0.02 s on,1.08 s off)using a programmable electric current to rapidly switch the reaction between high(for example,up to 2,400 K)and low temperatures.

In-situ microstructural investigations of the TRIP-to-TWIP evolution in Ti-Mo-Zr alloys as a function of Zr concentration

Aiming at overcoming the strength-ductility trade-off in structural Ti-alloys,a new family of TRIP/TWIP Ti-alloys was developed in the past decade(TWIP:twinning-induced plasticity;TRIP:transformationinduced plasticity).Herein,we study the tunable nature of deformation mechanisms with various TWIP and TRIP contributions by fine adjustment of the Zr content on ternary Ti-12 Mo-xZr(x=3,6,10)alloys.The microstructure and deformation mechanisms of the Ti-Mo-Zr alloys are explored by using in-situ electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that a transition of the dominant deformation mode occurred,going from TRIP to TWIP major mechanism with increasing Zr content.In the Ti-12 Mo-3 Zr alloy,the stress-induced martensitic transformation(SIM)is the major deformation mode which accommodates the plastic flow.Regarding the Ti-12 Mo-6 Zr alloy,the combined deformation twinning(DT)and SIM modes both contribute to the overall plasticity with enhanced strain-hardening rate and subsequent large uniform ductility.Further increase of the Zr content in Ti-12 Mo-10 Zr alloy leads to an improved yield stress involving single DT mode as a dominant deformation mechanism throughout the plastic regime.In the present work,a set of comprehensive in-situ and ex-situ microstructural investigations clarify the evolution of deformation microstructures during tensile loading and unloading processes.

Differences in the acoustic characteristics of DC bias alternating arcs in argon,helium,and nitrogen

The acoustic effects of gas discharge plasma have received much attention.Previous studies have shown that cold plasma and thermal plasma have different principles of sound generation.In this paper,the differences in the acoustic characteristics of DC bias alternating arc plasma(thermal plasma)in different gas environments(argon,helium,and nitrogen)are investigated by combining experiments and simulations.Many processes in industrial machining involve this arc plasma.It was found that the acoustic characteristics of the arcs of these three gases are significantly different.The two key parameters,electrical and thermal conductivity of the gas,determine the acoustic characteristics of the arc by influencing the electric power of the arc and the heat dissipation through the anode.At the same drive current,the nitrogen arc has the largest voltage drop and the helium arc has the highest electroacoustic conversion efficiency.This results in the acoustic pressure amplitude being helium,nitrogen,and argon in descending order.The research contributes to a deeper understanding of the vocalization mechanism of arc plasma and provides theoretical guidance on gas selection for arc acoustic wave applications.

Asymmetric nonlinear-mode-conversion in an optical waveguide with PT symmetry

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect,while it is challenging to achieve asymmetric nonlinear-mode-conversion(NMC)due to the limitations imposed by phase-matching.In this work,we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequencydoubling process and periodic PT symmetric modulation in an optical waveguide.By engineering the one-way momentum from PT symmetric modulation,we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes.Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry,which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.

Effect of photoionisation on initial discharge in air under nanosecond pulse voltage

Effects of photoionisation on the development and electron runaway of the initial discharge in atmospheric air under nanosecond pulse voltage were studied via twodimensional particle-in-cell/Monte Carlo collision simulations.It was found that photoionisation has little effect at the beginning of the initial discharge.However,as the discharge channel gradually develops towards the anode,photoionisation shows greater impacts on the morphology of discharge but has little influence on the velocity of discharge development.Photoionisation does not appear to have a decisive effect on the growth trend of the highest energy of runaway electrons,but it does affect the change rate of the highest energy and overall distribution of electron energy,resulting in a higher proportion of energetic electrons.The difference in the distributions of the electron energy between the two cases,with and without considering photoionisation,can be attributed to the impact of photoionisation on the discharge morphology,which in turn distorted the electric field.The spatial density distributions of the electrons produced by photoionisation further explained the differences.The authors’results explicitly demonstrate the influence of photoionisation on the development and the electron runaway of the initial discharge under nanosecond pulse voltage,which provides more comprehensive knowledge for the atmospheric air gap nanosecond pulse discharge physics.

Similarity of gas discharge in low-pressure argon gaps between two plane-parallel electrodes

The similarity of gas discharge in low-pressure argon gaps between two plane-parallel electrodes was investigated by experiments,numerical simulations and theoretical analysis.It was found by the experiments that the breakdown voltages depend not only on the product of gas pressure and gap length,but also on the aspect ratio of the gap,i.e.U_(b)=f(pd,d/r).It was theoretically proved that U_(b)=f(pd,d/r)is also a special case,the non-uniform electric field between plane-parallel electrodes,of similarity theorem of gas discharge.It was found by the experiments that there exist similar glow discharges only in two gaps with a limited scaled-down factor k.By theoretical analysis,it was explained that the forbidden processes such as the stepwise ionisation and the inelastic collision of the second kind violate the similarity of discharge as k increases,which was verified by the numerical simulations of the discharges with or without these two forbidden processes taken into account.

Compressive deformation-induced hierarchical microstructure in a TWIPβTi-alloy

The deformation mode of{332}<113>twinning(hereafter called 332T)has often been observed under the plastic flow in metastableβtitanium alloys with body-centered cubic(BCC)structure,which contributes to improving the mechanical performance.Herein,we report a structure of compressive deformation-induced primary 332T with hierarchical and/or heterogeneous composite sub-structure in a Twin-Induced Plasticity(TWIP)βTi-alloy under uniaxial compression.The detailed structural characterization after compressive deformation revealed that the sub-structure,including secondary 332T and secondary{112}<111>twinning,formed inside the 332T structure,which constitutes a hierarchical and/or heterogeneous structure at micro-and nano-scale and consequently contributes to the high strength,large ductility and enhanced strain-hardening behavior.

Optical beam splitting and asymmetric transmission in bi-layer metagratings

In this work, inspired by advances in twisted two-dimensional materials, we design and study a new type of optical bi-layer metasurface system, which is based on subwavelength metal slit arrays with phase-gradient modulation, referred to as metagratings(MGs). It is shown that due to the found reversed diffraction law, the interlayer interaction that can be simply adjusted by the gap size can produce a transition from optical beam splitting to high-efficiency asymmetric transmission of incident light from two opposite directions. Our results provide new physics and some advantages for designing subwavelength optical devices to realize efficient wavefront manipulation and one-way propagation.

Guest Editorial: Understanding low temperature plasmas for device reliability, modulation and application to green energy strategy

Low temperature plasma stands at the forefront of green and clean energy technologies,showcasing remarkable versatility across a wide array of applications including material processing,water splitting,methane conversion,and plasma medicine.To fully harness the potential of this technology,it is imperative to deepen our understanding of the physics underlying various discharge structures.