Articles de revues sur le sujet « Conversions Stokes et anti-Stokes »

In this paper, the available potential energy (APE) framework of Winters et al. (J. Fluid Mech., vol. 289, 1995, p. 115) is extended to the fully compressible Navier–Stokes equations, with the aims of clarifying (i) the nature of the energy conversions taking place in turbulent thermally stratified fluids; and (ii) the role of surface buoyancy fluxes in the Munk & Wunsch (Deep-Sea Res., vol. 45, 1998, p. 1977) constraint on the mechanical energy sources of stirring required to maintain diapycnal mixing in the oceans. The new framework reveals that the observed turbulent rate of increase in the background gravitational potential energy GPEr, commonly thought to occur at the expense of the diffusively dissipated APE, actually occurs at the expense of internal energy, as in the laminar case. The APE dissipated by molecular diffusion, on the other hand, is found to be converted into internal energy (IE), similar to the viscously dissipated kinetic energy KE. Turbulent stirring, therefore, does not introduce a new APE/GPEr mechanical-to-mechanical energy conversion, but simply enhances the existing IE/GPEr conversion rate, in addition to enhancing the viscous dissipation and the entropy production rates. This, in turn, implies that molecular diffusion contributes to the dissipation of the available mechanical energy ME = APE + KE, along with viscous dissipation. This result has important implications for the interpretation of the concepts of mixing efficiency γmixing and flux Richardson number Rf, for which new physically based definitions are proposed and contrasted with previous definitions.The new framework allows for a more rigorous and general re-derivation from the first principles of Munk & Wunsch (1998, hereafter MW98)'s constraint, also valid for a non-Boussinesq ocean: where G(KE) is the work rate done by the mechanical forcing, Wr, forcing is the rate of loss of GPEr due to high-latitude cooling and ξ is a nonlinearity parameter such that ξ = 1 for a linear equation of state (as considered by MW98), but ξ < 1 otherwise. The most important result is that G(APE), the work rate done by the surface buoyancy fluxes, must be numerically as large as Wr, forcing and, therefore, as important as the mechanical forcing in stirring and driving the oceans. As a consequence, the overall mixing efficiency of the oceans is likely to be larger than the value γmixing = 0.2 presently used, thereby possibly eliminating the apparent shortfall in mechanical stirring energy that results from using γmixing = 0.2 in the above formula.

Upconversion has attracted much attention for the potential applications of nanomaterials and bulk materials. Upconversion nanoprobes and sensors rely on the non-linear emission of the reporters, which present a low efficiency due to their anti-Stokes nature. For these two reasons, the materials require accurate and contrastable efficiency measurements, typically by measuring the absolute upconversion quantum yield (UCQY). The methodology for such measurements will vary from traditional photoluminescence quantum yield techniques that have been applied for downshifting materials [1]. Effects like the scattering, broadband absorption and reemission, inner-filter effects, thickness, self-absorption, and temperature, have to be considered [2]. This presentation will focus on some of these effects. The scattering has usually been neglected, however systems with scattering can increase the power density and subsequently the UCQY, as demonstrated both experimentally and via simulations [3]. Furthermore, this energy concentration also provides a new method for identifying the refractive index of phosphors, which is useful since some phosphors cannot be produced in macroscopic sizes. Broadband characterisation enables a route for characterisation exploiting the wide energy levels at the near-infrared. However, it introduces new challenges such as reemission [4]. In the case of applications that use a thick upconverted, the thickness is also a key parameter that can be responsible up to 50% of the emission [5]. Finally, one of the applications that is been intensively researched is the use of upconverting and downshifting nanoparticles as temperature reporters. Absolute upconversion photoluminescence quantum yield characterisation for different probes will be presented with a modified integrating sphere that allows in-situ absorption and emission measurements. References: [1] Callum M. S. Jones, Anna Gakamsky & Jose Marques-Hueso (2021) The upconversion quantum yield (UCQY): a review to standardize the measurement methodology, improve comparability, and define efficiency standards, Science and Technology of Advanced Materials, 22:1, 810-848, DOI: 10.1080/14686996.2021.1967698 [2] Callum M. S. Jones, Daniel Biner, Stavros Misopoulos, et al. Optimized photoluminescence quantum yield in upconversion composites considering the scattering, inner-filter effects, thickness, self-absorption, and temperature. Sci Rep 11, 13910 (2021). DOI:10.1038/s41598-021-93400-8 [3] Callum M. S. Jones, Nikita Panov, Artiom Skripka, et al., "Effect of light scattering on upconversion photoluminescence quantum yield in microscale-to-nanoscale materials," Opt. Express 28, 22803-22818 (2020). DOI: 10.1364/OE.398353 [4] Sean K. W. MacDougall, Aruna Ivaturi, Jose Marques-Hueso, et al; “Measurement procedure for absolute broadband infrared up-conversion photoluminescent quantum yields: Correcting for absorption/re-emission”. Rev Sci Instrum, 85 (6), 063109 (2014). DOI:10.1063/1.4881537 [5] Alessandro Boccolini, Jose Marques-Hueso, and Bryce S. Richards, "Self-absorption in upconverter luminescent layers: impact on quantum yield measurements and on designing optimized photovoltaic devices," Opt. Lett. 39, 2904-2907 (2014). DOI: 10.1364/OL.39.002904 Figure 1

The paper presents and discusses data for the ventilation airflow in an isothermal room corresponding to the Nielsen et al. (1978) test computed with Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) approaches. As LES computations provide directly both the speed and velocity components data, the difference between the mean speed and mean velocity values is computed and discussed. For the RANS computations that give the mean velocity data only, application of the velocity-to-speed conversion procedure based on the turbulence kinetic energy field provided by a turbulence model resulted in accurate mean speed evaluation.

La combustion est un sujet d’intérêt pour une large variété de domaines d’applications civils ou militaires. Comprendre les phénomènes physico-chimiques à l’oeuvre dans ces milieux complexes, et les décrire à l’aide de modèles éprouvés, sont des enjeux majeurs qui requièrent des mesures fiables et quantitatives. La spectroscopie par diffusion Raman anti-Stokes cohérente (DRASC ou CARS en anglais) a démontré des performances inégalées pour la mesure de température. Cette technique a été implémentée avec de nombreuses architectures laser, et appliquée avec succès à un large éventail de milieux.

Correction for ‘Enhanced anti-stocks luminescence in LaNbO₄:Ln³⁺ (Ln³⁺ = Yb³⁺, Er³⁺/Ho³⁺/Tm³⁺) with abundant color’ by Huining Huang et al., RSC Adv., 2017, 7, 16777–16786.

From the famous 1918 H1N1 influenza to the present COVID-19 pandemic, the need for improved viral detection techniques is all too apparent. The aim of the present paper is to show that identification of individual virus particles in clinical sample materials quickly and reliably is near at hand. First of all, our team has developed techniques for identification of virions based on a modular atomic force microscopy (AFM). Furthermore, femtosecond adaptive spectroscopic techniques with enhanced resolution via coherent anti-Stokes Raman scattering (FASTER CARS) using tip-enhanced techniques markedly improves the sensitivity [M. O. Scully,et al.,Proc. Natl. Acad. Sci. U.S.A.99, 10994–11001 (2002)].

Purpose Low membrane durability remains a major challenge in anion exchange membrane fuel cells (AEMFCs). This is despite the AEMFCs’ proven potential to eliminate the dependency of Fuel cells on Pt catalysts and bring about the mass commercialization of the technology. This problem can be effectively addressed through combined optimization of the AEMFCs’ operating conditions during evaluation, followed by finetuning of the membrane chemistry to address any observed weaknesses. After synthesis, water distribution is the primary operation condition determining a given AEM’s performance and lifespan [1]. This is partly because water affects the ionic conductivity and, thus, maximum current density, which is known to play a significant role in the longevity of membranes. Therefore, establishing the water distribution during power generation for any given membrane is highly desirable. For this to happen, suitable and reliable techniques must exist to measure and compare the water distribution in situ and operando. In this paper, we used in-house assembled Raman spectroscopy and coherent anti-Stokes Raman scattering spectroscopy (CARS) systems to measure the water in an operational AEMFC for the first time. CARS comes with a high time resolution of 0.1 s, which is essential in the transient response study of FCs. Experimental Method QPAF-4 membrane film (Fig. 1) of the thickness of 30 µm and IEC of 2.0 meq g-1 was solution cast as reported [2]. The cell was then assembled, as reported [3]. An airtight transparent quartz window 200 μm thick was mounted at the cathode endplate for optical access to the QPAF-4 membrane through a 500 mm pinhole in the GDE. A thin Pt disk was placed on the opposite side of the membrane to reflect the signal to the spectrometer through the ×50 objective lens used. For Raman spectroscopy, a 632 nm, 1 mW laser with 5.5 min total exposure was used. For CARS, an 11 mW 785nm pump laser and 16 mW Stokes laser with 200 ms total exposure were used. The flow rate was 100 ml min-1 for all gases. The cell temperature was maintained at 60 °C. The relative humidity of the gas varied from 30% to 100% in steps of 10% RH. The system was allowed to stabilize for 3 hours at each humidity level before measurement. Results and discussion Figures 2 and 3 show the normalized in situ spectra recorded at the center of the membrane at different relative humidity values using CARS and Raman, respectively. The peak positions are comparable. However, the OH peak in CARS is taller relative to C=C than in Raman. CARS signal intensity is generally stronger than Raman [3]. Within the CARS peak, the purely OH portion of the signal is more prominent relative to the rest of the peak than in Raman. This is attributed to the fact that the Infrared laser associated with the stokes light (817-1144nm) of CARS is known to be more sensitive to OH vibration than the lower wavelength laser (632nm) used in Raman [4]. Conclusion We successfully developed a 785nm CARS system capable of operando water measurement in AEMFCs. The results from this technique are comparable to those from micro-Raman spectroscopy but with better signal intensity and time resolution. This increases the number of practical methods available to researchers interested in measuring water content in AEMFCs allowing for faster development of the technology. The water distribution results during power generation will be discussed at the conference. With CARS, higher temporal/time resolution is achieved, which is advantageous when cell response needs to be studied. References [1] K. Otsuji et al. J. Power Sources, 522, 230997 (2022). [2] H. Ono et al. J. Mater. Chem. A, 5, 24804 (2017). [3] H. Nishiyama et al. J. Phys. Chem. C, 124, 9703 (2020). [4] Y. Horiba Jobin, “Raman Spectroscopy for Analysis and Monitoring,” (2017). Figure 1

We have carried out wall-resolved unstructured fully compressible Navier–Stokes simulations of a complete standing-wave thermoacoustic–piezoelectric engine model inspired by the experimental work of Smoker et al. (J. Appl. Phys., vol. 111 (10), 2012, 104901). The model is axisymmetric and comprises a 51 cm long resonator divided into two sections: a small-diameter section enclosing a thermoacoustic stack and a larger-diameter section capped by a piezoelectric diaphragm tuned to the thermoacoustically amplified mode (388 Hz). The diaphragm is modelled with multi-oscillator broadband time-domain impedance boundary conditions (TDIBCs), providing higher fidelity over single-oscillator approximations. Simulations are first carried out to the limit cycle without energy extraction. The observed growth rates are shown to be grid convergent and are verified against a numerical dynamical model based on Rott’s theory. The latter is based on a staggered grid approach and allows jump conditions in the derivatives of pressure and velocity in sections of abrupt area change and the inclusion of linearized minor losses. The stack geometry maximizing the growth rate is also found. At the limit cycle, thermoacoustic heat leakage and frequency shifts are observed, consistent with experiments. Upon activation of the piezoelectric diaphragm, steady acoustic energy extraction and a reduced pressure amplitude limit cycle are obtained. A heuristic closure of the limit cycle acoustic energy budget is presented, supported by the linear dynamical model and the nonlinear simulations. The developed high-fidelity simulation framework provides accurate predictions of thermal-to-acoustic and acoustic-to-mechanical energy conversion (via TDIBCs), enabling a new paradigm for the design and optimization of advanced thermoacoustic engines.

The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actinrelated proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of ∼13 × 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 μM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actinrich regions of Acanthamoeba.

Being atomically thin, flexible, and exhibiting considerable light emission and ultrafast non-equilibrium dynamics, semiconducting transition metal dichalcogenides (TMDs) have been considered as promising candidates for next-generation optoelectronic devices. The optical and electronic properties of TMDs are governed by a rich landscape of tightly bound excitons, including regular bright excitons, as well as optically inaccessible dark exciton states. Recently, strain engineering of monolayer TMDs has been introduced to tune their optical properties, such as the exciton transition energy, exciton-phonon coupling, or the Stokes shift [1-3]. Transport of charge carriers is crucial for nanoelectronics. In conventional materials, electronic transport can be conveniently controlled by external electric fields. However, the tightly bound excitons, being neutral particles, are only weakly affected by electrical fields. We demonstrate that mechanical strain can also be used to manipulate the transport of excitons in TMDs. To this end, we apply homogeneous tensile strain to a WS2 monolayer by bending the substrate [1], which causes a redshift of the X0 exciton photoluminescence. By measuring the spatiotemporal photoluminescence after near-resonant excitation with femtosecond laser pulses, we map the spread of excitons and extract the strain-dependent diffusion coefficient [4]. Furthermore, we demonstrate the propagation of excitons in an inhomogeneous strain landscape. We create inhomogeneous tensile strain in TMD monolayers by transferring them onto patterned substrates with nanopillars or by a nanoimprint technique [5]. Due to the redshift of the exciton resonances with applied strain, excitons are expected to move towards high-strain regions in an inhomogeneous strain field - the so-called "funneling" effect. We verify this behavior for the "bright" TMD material monolayer MoSe2. In the case of the "dark" monolayer WS2, we observe exactly the opposite effect. Here, the excitons are expelled from the high-strain regions ("anti-funneling") [6]. By comparing our experimental results with a microscopic theory, we explain this observation by the drift of momentum-dark KΛ excitons, which, in contrast to bright excitons, shift to higher energies with strain. Our joint experiment-theory study highlights the dominant role of momentum-dark excitons for the dynamics in monolayer TMDs and provides crucial design guidelines for TMD devices based on exciton transport. References [1] J. Roldan et al., Journal of Physics: Condensed Matter 27, 313201 (2015) [2] I. Niehues et al., Nano Letters 18, 1751 (2018) [3] I. Niehues et al., Nanoscale 12, 20786 (2020) [4] R. Rosati et al., 2D Materials 8, 015030 (2021) [5] J. Bensmann et al., arXiv:2212.11873 (2022) [6] R. Rosati et al., Nature Communications 12, 7221 (2021)

The first applications of luminescent nanocrystals to bioimaging were semiconductor quantum dots with optoelectronic properties that largely mirror those of organics and proteins, but with substantially increased stability and brightness that have enabled single molecule and other challenging imaging applications. Building on this success, newer nanocrystals have been engineered with optical properties unlike anything found in traditional probes, including perfect photostability,1,2 anti-Stokes emission a billion-fold more efficient than 2-photon excitation,3 and most recently, photon avalanches hosted within nanostructures.4 Avalanches are steeply nonlinear events in which outsized responses arise from a series of minute inputs. With light, photon avalanching (PA) had been observed only in bulk materials and aggregates, often at cryogenic temperatures, preventing its application to bioimaging. We recently reported the realization of PA at room temperature in sub-30 nm Tm3+-doped NaYF4 upconverting nanoparticles (UCNPs) and demonstrated their use in high-resolution imaging at wavelengths that fall within NIR spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by either continuous-wave or pulsed lasers and exhibit all of the defining features of PA: clear excitation power thresholds, exceptionally long rise time at threshold, and a dominant excited-state absorption that is >10,000 times larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales with up to the 31st power of pump intensity, an extreme nonlinearity caused by the induced positive optical feedback within each nanocrystal. This enables sub-70 nm spatial resolution using only simple scanning confocal microscopy and before any computational data analysis. NaYF4 ANPs with 8-20% Tm3+content can be excited at either 1064 or 1450 nm, with avalanching emission at 800 nm. Pairing the steep nonlinearity of ANPs with existing superresolution techniques and computational methods allows for imaging with higher resolution and at ca. 100-fold lower excitation intensities than is possible with other probes. For application of ANPs to live-cell imaging, we have developed synthetic chemistry-free methods for conjugating engineered antibodies to NP-surface SpyCatcher proteins,5 which bind and spontaneously form covalent isopeptide bonds with cognate SpyTag peptides. This enables controlled and irreversible attachment of antibodies to nanoparticle surfaces, for specific targeting of cell-surface receptors in quantitative live-cell study of their distribution, trafficking, and physiology. Wu, S. et al. Non-blinking and photostable upconverted luminescence from single lanthanide-doped nanocrystals. Proc. Natl. Acad. Sci. 106, 10917–10921 (2009). Fernandez-Bravo, A. et al. Continuous-wave upconverting nanoparticle microlasers. Nat. Nanotechnol. 13, 572–577 (2018). Tian, B. et al. Low irradiance multiphoton imaging with alloyed lanthanide nanocrystals. Nat. Commun. 9, 3082 (2018). Lee, C. et al. Giant nonlinear optical responses from photon-avalanching nanoparticles. Nature 589, 230–235 (2021). Pedroso, C. C. S. et al. Immunotargeting of nanocrystals by SpyCatcher conjugation of engineered antibodies. ACS Nano 15, 18374–18384 (2021). Figure 1

BackgroundSystemic sclerosis (SSc) is an immune-mediated connective tissue disease with clinical hallmark of inflammation, vasculopathy and fibrosis resulting in abnormal collagen and intercellular matrix formation in the dermis and internal organ. Skin severity correlates with systemic complications and mortality in SSc.Many skin assessment tools studied do not fulfilled all standards set by OMERACT which include criterion validity, construct validity, discrimination, responsiveness, reliability and feasibility.Modified Rodnan skin score (mRSS) is commonly used as outcome measure in clinical trials of SSc. It is however, limited by inter-rater variability. Studies also showed that skin biopsy samples from body part of SSc patients with clinically normal mRSS had demonstrable pathological deposition of collagen. While repeat skin biopsy to track longitudinally, may be unacceptable to patients. Hence, ongoing research for non-invasive tools are encouraged.ObjectivesWe follow through our previous work studying commercially available non-invasive imaging tools in SSc skin assessment by using Coherent-Raman scattering microscopy (CRS).MethodsSkin biopsies of 4mm were obtained from SSc (n=3) and HC (n=1). Skin samples were collected at anterior surface of forearm from newly diagnosed diffuse SSc which were treatment naïve. Samples were frozen at -80c prior to analysis under CRS at skin depth of 150-200um. The laser setting was 3% pump (802nm) and 6% stokes (1045nm) to avoid tissue burn. 3 contrast methods used are Coherent anti-Stokes Raman scattering (CARS) for imaging of lipids, Second Harmonic Generation (SHG) for collagen and Two-Photon Fluorescence (TPF) for elastin fibers. We analysed collagen and elastin fibers in the skin samples which is disease relevant end products of fibroblast activation in SSc. Descriptive study of the skin CRS characteristics is reported.ResultsThe SHG analysis revealed denser collagen fibers in dermal layer of diseased skin. It also appears that the collagen deposition occurs in more superficial layers of the skin. Peak of collagen curve were at depth of 110-130um HC vs 75-90um in SSc. Collagen fibres were more aligned in the SSc (Figure 1).Figure 1.Microscopy analysis of SSc (B) vs HC (A) skin. I: 3D image of biopsy samples with three contrasts. Red is CARS for lipid, blue is SHG for collagen and green is TPF for elastin fibers. II. SHG. Imaging revealed denser and more aligned collagen fibers in SSc.Furthermore, TPF revealed larger number of disordered elastin fibres in the dermal layer of SSc than HC.ConclusionNailfold capillaroscopy is used to define and stage micro-vasculopathy in SSc. Inflammatory pro-fibrotic processes on the other hand cause abnormal collagen and intercellular matrix formation in the dermis and internal organ.With the demand of better tools in diagnosis of early SSc and therapeutic research, our work with CRS prove better in objective evaluation of skin changes at the molecular level. Here, we demonstrate that the SHG is altered in the early diffuse SSc skin with increased and aligned collagen in the SSc dermis compatible with mRSS score. Others have observed this alignment of the collagen, and we have published that SSc fibroblasts migrate/invade along aligned collagen and modify the underlying extracellular matrix, adding collagens I and III, cross-linking enzymes and other factors including TSP-1.Our future work include:1.Generating a computer module in defining pathological collagen level2.Analysis of metabolites and pathological pathways in SSc3.In-vivo trials with novel therapeutic peptides.4.Lastly, manufacturing of non-invasive handheld device that is capable of diagnosis subclinical SSc and for outcome measure in clinical-therapeutic researchReferences[1]Abignano G, et al. Virtual skin biopsy by optical coherence tomography: the first quantitative imaging biomarker for scleroderma. Ann Rheum Dis. 2013[2]Ahmed Abdi B, et.al. Use of Patterned Collagen Coated Slides to Study Normal and Scleroderma Lung Fibroblast Migration. Sci Rep. 2017AcknowledgementsWe want to acknowledge our colleagues and patients in Royal Free Hospital, to make this project a success.Disclosure of InterestsNone declared

For improving the generality, expandability and accuracy, the general embedded intelligent monitoring system of tower crane is developed. The system can be applied to different kinds of tower cranes running at any lifting ratio, can be initialized using U disk with the information of tower crane, and fit the lifting torque curve automatically. In dangerous state, the system can sent out alarm signals with sounds and lights, and cut off power by sending signals to PLC through communication interface RS485. When electricity goes off suddenly, the system can record the real-time operating information automatically, and store them in a black box, which can be taken as the basis for confirming the accident responsibility.In recent years, tower cranes play a more and more important role in the construction of tall buildings, in other construction fields are also more widely used. For the safety of tower cranes, various monitors have been developed for monitoring the running information of crane tower [1-8]. These monitors can’t eliminate the errors caused by temperature variations automatically. The specific tower crane’s parameters such as geometric parameters, alarming parameters, lifting ratio, lifting torque should be embedded into the core program, so a monitor can only be applied to a specific type of tower crane, lack of generality and expansibility.For improving the defects of the existing monitors, a general intelligent monitoring modular system of tower crane with high precision is developed, which can initialize the system automatically, eliminate the temperature drift and creep effect of sensor, and store power-off data, which is the function of black box.Hardware design of the monitoring systemThe system uses modularized design mode. These modules include embedded motherboard module, sensor module, signal processing module, data acquisition module, power module, output control module, display and touch screen module. The hardware structure is shown in figure 1. Figure 1 Hardware structure of the monitoring systemEmbedded motherboard module is the core of the system. The motherboard uses the embedded microprocessor ARM 9 as MCU, onboard SDRAM and NAND Flash. Memory size can be chosen according to users’ needs. SDRAM is used for running procedure and cache data. NAND Flash is used to store embedded Linux operating system, applications and operating data of tower crane. Onboard clock with rechargeable batteries provides the information of year, month, day, hour, minute and second. This module provides time tag for real-time operating data. Most interfaces are taken out by the plugs on the embedded motherboard. They include I/O interface, RS232 interface, RS485 interface, USB interface, LCD interface, Audio interface, Touch Screen interface. Pull and plug structure is used between all interfaces and peripheral equipments, which not only makes the system to be aseismatic, but also makes its configuration flexible. Watch-dog circuit is designed on the embedded motherboard, which makes the system reset to normal state automatically after its crash because of interference, program fleet, or getting stuck in an infinite loop, so the system stability is improved greatly. In order to store operating data when power is down suddenly, the power-down protection circuit is designed. The saved data will be helpful to repeat the accident process later, confirm the accident responsibility, and provide the basis for structure optimization of tower crane.Sensor module is confirmed by the main parameters related to tower crane’s security, such as lifting weight, lifting torque, trolley luffing, lifting height, rotary angle and wind speed. Axle pin shear load cell is chosen to acquire lifting weight signals. Potentiometer accompanied with multi-stopper or incremental encoder is chosen to acquire trolley luffing and lifting height signals. Potentiometer accompanied with multi-stopper or absolute photoelectric encoder is chosen to acquire rotary angle signals. Photoelectric sensor is chosen to acquire wind speed signals. The output signals of these sensors can be 0~5V or 4~20mA analog signals, or digital signal from RS485 bus. The system can choose corresponding signal processing method according to the type of sensor signal, which increases the flexibility on the selection of sensors, and is helpful for the users to expand monitoring objects. If the acquired signal is analog signal, it will be processed with filtering, isolation, anti-interference processing by signal isolate module, and sent to A/D module for converting into digital signals, then transformed into RS485 signal by the communication protocol conversion device according to Modbus protocol. If the acquired signal is digital signal with RS485 interface, it can be linked to RS485 bus directly. All the acquired signals are sent to embedded motherboard for data processing through RS485 bus.The data acquisition module is linked to the data acquisition control module on embedded motherboard through RS485 interface. Under the control of program, the system inquires the sensors at regular intervals, and acquires the operating data of crane tower. Median filter technology is used to eliminate interferences from singularity signals. After analysis and processing, the data are stored in the database on ARM platform.Switch signal can be output to relay module or PLC from output control module through RS485 bus, then each actuator will be power on or power off according to demand, so the motion of tower crane will be under control.Video module is connected with motherboard through TFT interface. After being processed, real-time operating parameters are displayed on LCD. The working time, work cycle times, alarm, overweight and ultar-torque information will be stored into database automatically. For meeting the needs of different users, the video module is compatible with 5.7, 8.4 or 10.4 inches of color display.Touch screen is connected with embedded motherboard by touch screen interface, so human machine interaction is realized. Initialization, data download, alarm information inquire, parameter modification can be finished through touch screen.Speaker is linked with audio interface, thus alarm signals is human voice signal, not harsh buzz.USB interface can be linked to conventional U disk directly. Using U disk, users can upload basic parameters of tower crane, initialize system, download operating data, which provides the basis for the structural optimization and accident analysis. Software design of the monitoring systemAccording to the modular design principle, the system software is divided into grading encryption module, system update module, parameter settings module, calibration module, data acquisition and processor module, lifting parameters monitoring module, alarm query module, work statistics module.Alarm thresholds are guarantee for safety operation of the tower crane. Operating data of tower crane are the basis of service life prediction, structural optimization, accident analysis, accident responsibility confirmation. According to key field, the database is divided into different security levels for security requirements. Key fields are grade encryption with symmetrical encryption algorithm, and data keys are protected with elliptic curve encryption algorithm. The association is realized between the users’ permission and security grade of key fields, which will ensure authorized users with different grades to access the equivalent encrypted key fields. The user who meets the grade can access equivalent encrypted database and encrypted key field in the database, also can access low-grade encrypted key fields. This ensures the confidentiality and integrity of key data, and makes the system a real black box.The system is divided into operating mode and management mode in order to make the system toggle between the two states conveniently. The default state is operating mode. As long as the power is on, the monitoring system will be started by the system guide program, and monitor the operating state of the tower crane. The real-time operating data will be displayed on the display screen. At the dangerous state, warning signal will be sent to the driver through voice alarm and light alarm, and corresponding control signal will be output to execution unit to cut off relevant power for tower crane’s safety.By clicking at the mode switch button on the initial interface, the toggle can be finished between the management mode and the operating mode. Under the management mode, there are 4 grades encrypted modes, namely the system update, alarm query, parameter setting and data query. The driver only can browse relevant information. Ordinary administrator can download the alarm information for further analysis. Senior administrator can modify the alarm threshold. The highest administrator can reinitialize system to make it adapt to different types of tower crane. Only browse and download function are available in the key fields of alarm inquiry, anyone can't modify the data. The overload fields in alarm database are encrypted, only senior administrator can browse. The sensitive fields are prevented from being tampered to the great extent, which will provide the reliable basis for the structural optimization and accident analysis. The system can be initialized through the USB interface. Before initialization, type, structural parameters, alarm thresholds, control thresholds, lifting torque characteristics of tower crane should be made as Excel files and then converted to XML files by format conversion files developed specially, then the XML files are downloaded to U disk. The U disk is inserted into USB interface, then the highest administrator can initialize the system according to hints from system. After initialization, senior administrator can modify structural parameters, alarm thresholds, control thresholds by clicking on parameters setting menu. So long as users can make the corresponding excel form, the system initialization can be finished easily according to above steps and used for monitoring. This is very convenient for user.Tower crane belongs to mobile construction machinery. Over time, sensor signals may have some drift, so it is necessary to calibrate the system regularly for guaranteeing the monitoring accuracy. Considering the tower is a linear elastic structure, sensors are linear sensors,in calibration linear equation is used:y=kx+b (1)where x is sample value of sensor, y is actual value. k, b are calibration coefficients, and are calculated out by two-points method. At running mode, the relationship between x and y is:y=[(y1-y0)/(x1-x0)](x-x0)+y0 (2)After calibration, temperature drift and creep can be eliminated, so the monitoring accuracy is improved greatly.Lifting torque is the most important parameter of condition monitoring of tower crane. Comparing the real-time torque M(L) with rated torque Me(L), the movement of tower crane can be controlled under a safe status.M (L)= Q (L)×L (3)Where, Q(L)is actual lifting weight, L is trolley luffing. Me(L) = Qe(L)×L (4)Where, Q e(L) is rated lifting weight. The design values of rated lifting weight are discrete, while trolley luffing is continuous. Therefore there is a rated lifting weight in any position. According to the mechanical characteristics of tower crane, the rated lifting weight is calculated out at any point by 3 spline interpolation according to the rated lifting weight at design points.When lifting weight or lifting torque is beyond rated value, alarm signal and control signal will be sent out. The hoist motor with high, medium and low speed is controlled by the ratio of lifting weight Q and maximum lifting weight Qmax,so the hoisting speed can be controlled automatically by the lifting weight. The luffing motor with high and low speed is controlled by the ratio of lifting torque M and rated lifting torque Me. Thus the luffing speed can be controlled by the lifting torque automatically. The flow chart is shown in figure 2. Fig. 2 real-time control of lifting weight and lifting torqueWhen accidents take place, power will be off suddenly. It is vital for identifying accident liability to record the operating data at the time of power-off. If measures are not taken to save the operating data, the relevant departments is likely to shirk responsibility. In order to solve the problem, the power-off protection module is designed. The module can save the operating data within 120 seconds automatically before power is off suddenly. In this 120 seconds, data is recorded every 0.1 seconds, and stores in a 2D array with 6 rows 1200 columns in queue method. The elements of the first line are the recent time (year-month-day-hour-minute-second), the elements of the second line to sixth line are lifting weight, lifting torque, trolley luffing, lifting height and wind speed in turn. The initial values are zero, when a set of data are obtained, the elements in the first column are eliminated, the elements in the backward columns move frontwards, new elements are filled into the last column of the array, so the array always saves the operating data at the recent 120 seconds. In order to improve the real-time property of the response, and to extend the service life of the nonvolatile memory chip EEPROM-93C46, the array is cached in volatile flip SDRAM usually. So long as power-off signal produces, the array will be shift to EEPROM, at once.In order to achieve the task, the external interruption thread and the power-off monitoring thread of program is set up, the power-off monitoring thread of program is the highest priority. These two threads is idle during normal operation. When power is off, the power-off monitoring thread of program can be executed immediately. When power-off is monitored by power-off control circuit, the external interruption pins produces interrupt signal. The ARM microprocessor responds to external interrupt request, and wakes up the processing thread of external interruption, then sets synchronized events as informing state. After receiving the synchronized events, the data cached in SDRAM will be written to EEPROM in time.ConclusionThe general intelligence embedded monitoring system of tower crane, which can be applicable to various types of tower crane operating under any lifting rates, uses U disk with the information of the tower crane to finish the system initialization and fits the lifting torque curve automatically. In dangerous state, the system will give out the voice and light alarm, link with the relay or PLC by the RS485 communication interface, and cut off the power. When power is down suddenly, the instantaneous operating data can be recorded automatically, and stored in a black box, which can be taken as the proof for identifying accident responsibility. The system has been used to monitor the "JiangLu" series of tower cranes successfully, and achieved good social and economic benefits.AcknowledgementsThe authors wish to thank China Natural Science Foundation(50975289), China Postdoctoral Science Foundation(20100471229), Hunan science & technology plan, Jianglu Machinery & Electronics Co. Ltd for funding this work.Reference Leonard Bernold. Intelligent Technology for Crane Accident Prevention. Journal of Construction Engineering and Management. 1997, 9: 122~124.Gu Lichen,Lei Peng,Jia Yongfeng. Tower crane' monitor and control based on multi-sensor. Journal of Vibration, Measurement and Diagnosis. 2006, 26(SUPPL.): 174-178.Wang Ming,Zhang Guiqing,Yan Qiao,et, al. Development of a novel black box for tower crane based on an ARM-based embedded system. Proceedings of the IEEE International Conference on Automation and Logistics. 2007: 82-87.Wang Renqun, Yin Chenbo, Zhang Song, et, al. Tower Crane Safety Monitoring and Control System Based on CAN Bus. Instrument Techniques and Sensor. 2010(4): 48-51.Zheng Conghai,Li Yanming,Yang Shanhu,et, al. Intelligent Monitoring System for Tower Crane Based on BUS Architecture and Cut IEEE1451 Standard. Computer Measurement & Control. 2010, 18, (9): 1992-1995.Yang Yu,Zhenlian Zhao,Liang Chen. Research and Design of Tower Crane Condition Monitoring and Fault Diagnosis System. 2010 Proceedings of International Conference on Artificial Intelligence and Computational Intelligence. 2010: 405-408.Yu Yang, Chen Liang, Zhao Zhenlian. Research and design of tower crane condition monitoring and fault diagnosis system. International Conference on Artificial Intelligence and Computational Intelligence, 2010, 3: 405-408.Chen Baojiang, Zeng Xiaoyuan. Research on structural frame of the embedded monitoring and control system for tower crane. 2010 International Conference on Mechanic Automation and Control Engineering. 2010: 5374-5377.

Quantum communication holds promise for absolutely secure information transmission. However, the direct transmission distance of quantum states is limited by the no-cloning theorem and transmission loss. To overcome these problems, Duan et al. proposed a promising quantum repeater scheme, DLCZ protocol (for Duan, Lukin, Cirac, and Zoller, in 2001), in which linear optics and atomic ensembles are used to combine entanglement generation and quantum memory into a single node. A quantum memory with highly retrieval efficiency is beneficial to increase the rate of entanglement swapping, achieving high-speed entanglement distribution. Up to now, high-efficiency quantum memories have been realized using high-optical-depth atomic ensembles or by coupling atomic ensembles with a medium-finesse optical cavity. However, the effect of the waist ratio of read beam and anti-Stokes photon modes on intrinsic retrieval efficiency has not been studied in detail. Here, we study the dependence of intrinsic retrieval efficiency on the waist ratio of read beam and anti-Stokes photon modes in cavity-enhanced quantum memory.<br>In this work, a <i>⁸⁷Rb</i> atomic ensemble, that is placed at the center of a passively stabilized polarization interferometer (BD_1,2), is used as quantum memory. Firstly, the ensemble is captured through magneto-optical trapping (MOT) and prepared to the Zeeman sub-level of ground state $|5{S_{1/2}},F = 1,m = 0\rangle$. Then, a weak write pulse, with frequency red-detuned from the $|5{S_{1/2}},F = 1,m = 0\rangle$$ \to |5{P_{1/2}},F' = 1,m = 1\rangle $ transition by 110 MHz, illuminates the atoms and induces spontaneous Raman scattering out a Stokes photon. In this regime of weak excitation, the detection of a Stokes photon heralds the storage of a single spin wave $|5{S_{1/2}},F = 1,m = 0\rangle$$ \leftrightarrow |5{S_{1/2}},F = 2,m = 0\rangle $ ($|5{S_{1/2}},F = 1,m = 0\rangle$$\leftrightarrow |5{S_{1/2}},F = 2,m = 2\rangle $) distributed among the whole ensemble. After a programmable delay, a read pulse, red-detuned from the $|5{S_{1/2}},F = 2,m = 0\rangle \to |5{P_{1/2}},F' = 2,m = - 1\rangle $ transition by 110MHz, transfer this spin wave into an anti-Stokes photon. We detect the Stokes photons and anti-Stokes photons with polarization ${\sigma ^ + }$, which means all the spin-wave are stored in a magnetic-field-insensitive state to reduce the decoherence caused by the stray magnetic fields. In order to increase the intrinsic retrieval efficiency, the atomic ensemble is placed in a ring cavity. The cavity length is 4 m, the finesse is measured to be ~15, and the escape efficiency of ring cavity is 52.9%. Both Stokes and anti-Stokes photon qubits are required to resonate with the ring cavity. To meet this requirement, a cavity-locking beam is injected into the cavity to stabilize the cavity length using a Pound-Drever-Hall locking scheme. Finally, we fixed the Stokes (anti-Stokes) photon modes waist and changed the waist ratio by changing the write beam (read beam) waist.<br>The experiment result show that when the waist ratio of read beam and anti-Stokes photon modes is 3, the intrinsic retrieval efficiency is up to 68.9±1.6% and normalized cross-correlation function g⁽²⁾ reaches 26.5±1.9. We built a theoretical model, the intrinsic retrieval efficiency increases with the rise of the waist ratio, which show that the intrinsic retrieval efficiency is up to the peak when the waist ratio is 3, and the intrinsic retrieval efficiency tends to be stable when the waist ratio continues to increase. The experiment agrees with the theory. In the future, we will improve the intrinsic retrieval efficiency by enhance the fineness of the optical cavity with optimizing the cavity parameters.

Direct numerical simulations of turbulent non-rotating and rotating plane Couette flow with a periodically modulated plate velocity are conducted to study the effect of modulated forcing on turbulent shear flows. The time-averaged shear Reynolds number is fixed at $Re_S = 3 \times 10^4$ , which results in a frictional Reynolds number of approximately $Re_\tau \approx 400$ . The modulating frequency is varied in the range $Wo\in (20,200)$ , while the modulating amplitude is kept fixed at $10\,\%$ of the shear velocity except to demonstrate that varying this parameter has minimal effect. The resulting shear at the plates is found to be independent of the forcing frequency, and equal to the non-modulated baseline. For the non-rotating simulations, two clear flow regions can be seen: a near-wall region that follows Stokes’ theoretical solution, and a bulk region that behaves similar to Stokes’ solutions but with an increased effective viscosity. For high driving frequencies, the amplitude response follows the scaling laws for modulated turbulence of von der Heydt et al. (Phys. Rev. E, vol. 67, 2003, 046308). Cyclonic rotation is not found to modify the system's behaviour in a substantial way, but anti-cyclonic rotation changes significantly the system's response to periodic forcing. We find that the persistent axial inhomogeneities introduced by mild anti-cyclonic rotation make it impossible to measure the propagation of the modulation adequately, while stronger anti-cyclonic rotation creates regions where the modulation travels instantaneously.

Abstract In the present work, the interaction mechanism of specific polyelectrolyte multilayers (PEMs), fabricated by layer-by-layer deposition of polydiallyldimethylammonium chloride (PDDA) and poly(sodium 4-styrenesulfonate) (PSS), is studied using atomic force microscopy. The underwater oil-repellency of PSS-capped PEMs was further explored by measuring the interaction forces between tetradecane droplets and PEMs-coated silica substrates under various salinities. The force curves were analyzed following the Stokes–Reynolds–Young–Laplace theoretical model. Desirable consistency was achieved between the experimental and theoretical calculations at low NaCl concentrations (0.1 mM and 1 mM); however, underestimation of the attractive force was found as the NaCl concentration increases to moderate (10 mM) and high (100 mM) levels. Discrepancy analyses and incorporated features toward a reduced surface charge density were considered based on the previous findings of the orientation of anionic benzenesulfonate moieties (Liu et al. in Angew Chem Int Ed 54(16):4851–4856, 2015. https://doi.org/10.1002/anie.201411992). Short-range steric hindrance interactions were further introduced to simulate “brush” effect stemming from nanoscale surface roughness. It is demonstrated in our work that the PSS-capped PEMs remains a stable underwater lipophobicity against high salinity, which renders it potential application in surface wetting modification and anti-fouling.

Photo by Sharon McCutcheon on Unsplash ABSTRACT COVID-19 highlighted a disproportionate impact upon marginalized communities that needs to be addressed. Specifically, a focus on equity rather than equality would better address and prevent the disparities seen in COVID-19. A distributive justice framework can provide this great benefit but will succeed only if the medical community engages in outreach, anti-racism measures, and listens to communities in need. INTRODUCTION COVID-19 disproportionately impacted communities of color and lower socioeconomic status, sparking political discussion about existing inequities in the US.[1] Some states amended their guidelines for allocating resources, including vaccines, to provide care for marginalized communities experiencing these inequities, but there has been no clear consensus on which guidelines states should amend or how they should be ethically grounded. In part, this is because traditional justice theories do not acknowledge the deep-seated institutional and interpersonal discrimination embedded in our medical system. Therefore, a revamped distributive justice approach that accounts for these shortcomings is needed to guide healthcare decision-making now and into the post-COVID era. BACKGROUND Three terms – health disparity, health inequities, and health equity – help frame the issue. A health disparity is defined as any difference between populations in terms of disease incidence or adverse health events, such as morbidity or mortality. In contrast, health inequities are health disparities due to avoidable systematic structures rooted in racial, social, and economic injustice.[2] For example, current data demonstrate that Black, Latino, Indigenous Americans, and those living in poverty suffer higher morbidity and mortality rates from COVID-19.[3] Finally, health equity is the opportunity for anyone to attain his or her full health potential without interference from systematic structures and factors that generate health inequities, including race, socioeconomic status, gender, ethnicity, religion, sexual orientation, or geography.[4] ANALYSIS Health inequities for people of color with COVID-19 have led to critiques of states that do not account for race in their resource allocation guidelines.[5] For example, the Massachusetts Department of Public Health revised its COVID-19 guidelines regarding resource allocation to patients with the best chance of short-term survival.[6] Critics have argued that this change addresses neither preexisting structural inequities nor provider bias that may have led to comorbidities and increased vulnerability to COVID-19. By failing to address race specifically, they argue the policy will perpetuate poorer outcomes in already marginalized groups. As the inequities in COVID-19 outcomes continue to be uncovered and the data continue to prove that marginalized communities suffered disproportionately, we, as healthcare providers, must reconsider our role in addressing the injustices. Our actions must be ethically grounded in the concept of justice. l. Primary Theories of Justice The principle of justice in medical ethics relates to how we ought to treat people and allocate resources. Multiple theories have emerged to explain how justice should be implemented, with three of the most prominent being egalitarianism, utilitarianism, and distributive. This paper argues that distributive justice is the best framework for remedying past actions and enacting systemic changes that may persistently prevent injustices. An egalitarian approach to justice states all individuals are equal and, therefore, should have identical access to resources. In the allocation of resources, an egalitarian approach would support a strict distribution of equal value regardless of one’s attributes or characteristics. Putting this theory into practice would place a premium on guidelines based upon first-come, first-served basis or random selection.[7] However, the egalitarian approach taken in the UK continues to worsen health inequities due to institutional and structural discrimination.[8] A utilitarian approach to justice emphasizes maximizing overall benefits and achieving the greatest good for the greatest number of people. When resources are limited, the utilitarian principle historically guides decision-making. In contrast to the egalitarian focus on equal distribution, utilitarianism focuses on managing distributions to maximize numerical outcomes. During the COVID-19 pandemic, guidelines for allocating resources had utilitarian goals like saving the most lives, which may prioritize the youthful and those deemed productive in society, followed by the elderly and the very ill. It is important to reconsider using utilitarian approaches as the default in the post-COVID healthcare community. These approaches fail to address past inequity, sacrificing the marginalized in their emphasis on the greatest amount of good rather than the type of good. Finally, a distributive approach to justice mandates resources should be allocated in a manner that does not infringe individual liberties to those with the greatest need. Proposed by John Rawls in a Theory of Justice, this approach requires accounting for societal inequality, a factor absent from egalitarianism and utilitarianism.[9] Naomi Zack elaborates how distributive justice can be applied to healthcare, outlining why racism is a social determinant of health that must be acknowledged and addressed.[10] Until there are parallel health opportunities and better alignment of outcomes among different social and racial groups, the underlying systemic social and economic variables that are driving the disparities must be fixed. As a society and as healthcare providers, we should be striving to address the factors that perpetuate health inequities. While genetics and other variables influence health, the data show proportionately more exposure, more cases, and more deaths in the Black American and Hispanic populations. Preexisting conditions and general health disparities are signs of health inequity that increased vulnerability. Distributive justice as a theoretical and applied framework can be applied to preventable conditions that increase vulnerability and can justify systemic changes to prevent further bias in the medical community. During a pandemic, egalitarian and utilitarian approaches to justice are prioritized by policymakers and health systems. Yet, as COVID-19 has demonstrated, they further perpetuate the death and morbidity of populations that face discrimination. These outcomes are due to policies and guidelines that overall benefit white communities over communities of color. Historically, US policy that looks to distribute resources equally (focusing on equal access instead of outcomes), in a color-blind manner, has further perpetuated poor outcomes for marginalized communities.[11] ll. Historical and Ongoing Disparities Across socio-demographic groups, the medical system exacerbates historical and current inequities. Members of marginalized races,[12] women,[13] LGBTQ people,[14] and poor people[15] experience trauma caused by discrimination, marginalization, and failure to access high-quality public and private goods. Through the unequal treatment of marginalized communities, these historic traumas continue. In the US, people of color do not receive equal and fair medical treatment. A meta-analysis found that Hispanics and Black Americans were significantly undertreated for pain compared to their white counterparts over the last 20 years.[16] This is partly due to provider bias. Through interviewing medical trainees, a study by the National Academy of Science found that half of medical students and residents harbored racist beliefs such as “Black people’s nerve endings are less sensitive than white people’s” or “Black people’s skin is thicker than white people’s skin.”[17] More than 3,000 Indigenous American women were coerced, threatened, and deliberately misinformed to ensure cooperation in forced sterilization.[18] Hispanic people have less support in seeking medical care, in receiving culturally appropriate care, and they suffer from the medical community’s lack of resources to address language barriers.[19] In the US, patients of different sexes do not receive the same quality of healthcare. Despite having greater health needs, middle-aged and older women are more likely to have fewer hospital stays and fewer physician visits compared to men of similar demographics and health risk profiles.[20] In the field of critical care, women are less likely to be admitted to the ICU, less likely to receive interventions such as mechanical ventilation, and more likely to die compared to their male ICU counterparts.[21] In the US, patients of different socioeconomic statuses do not receive the same quality of healthcare. Low-income patients are more likely to have higher rates of infant mortality, chronic disease, and a shorter life span.[22] This is partly due to the insurance-based discrimination in the medical community.[23] One in three deaths of those experiencing homelessness could have been prevented by timely and effective medical care. An individual experiencing homelessness has a life expectancy that is decades shorter than that of the average American.[24] lll. Action Needed: Policy Reform While steps need to be taken to provide equitable care in the current pandemic, including the allocation of vaccines, they may not address the historical failures of health policy, hospital policy, and clinical care to eliminate bias and ensure equal treatment of patients. According to an applied distributive justice framework, inequities must be corrected. Rather than focusing primarily on fair resource allocation, medicine must be actively anti-racist, anti-sexist, anti-transphobic, and anti-discriminatory. Evidence has shown that the health inequities caused by COVID-19 are smaller in regions that have addressed racial wealth gaps through forms of reparations.[25] Distributive justice calls for making up for the past using tools of allocation as well as tools to remedy persistent problems. For example, Brigham and Women’s Hospital in Boston, MA, began “Healing ARC,” a pilot initiative that involves acknowledgement, redress, and closure on an institutional level.[26] Acknowledgement entails informing patients about disparities at the hospital, claiming responsibility, and incorporating community ideas for redress. Redress involves a preferential admission option for Black and Hispanic patients to specialty services, especially cardiovascular services, rather than general medicine. Closure requires that community and patient stakeholders work together to ensure that a new system is in place that will continue to prioritize equity. Of note, redress could take the form of cash transfers, discounted or free care, taxes on nonprofit hospitals that exclude patients of color,[27] or race-explicit protocol changes (such as those being instituted by Brigham and Women’s Hospital that admit patients historically denied access to certain forms of medical care). In New York, for instance, the New York State Bar Association drafted the COVID-19 resolutions to ensure that emergency regulations and guidelines do not discriminate against communities of color, and even mandate that diverse patient populations be included in clinical trials.[28] Also, physicians must listen to individuals from marginalized communities to identify needs and ensure that community members take part in decision-making. The solution is not to simply build new health centers in communities of color, as this may lead to tiers of care. Rather, local communities should have a chance to impact existing hospital policy and should also use their political participation to further their healthcare interests. Distributive justice does not seek to disenfranchise groups that hold power in the system. It aims to transform the system so that those in power do not continue to obtain unfair benefits at the expense of others. The framework accounts for unjust historical oppression and current injustices in our system to provide equitable outcomes to all who access the system. In this vein, we can begin to address the flagrant disparities between communities that have always – and continue to – exist in healthcare today.[29] CONCLUSION As equality focuses on access, it currently fails to do justice. Instead of outcomes, it is time to focus on equity. A focus on equity rather than equality would better address and prevent the disparities seen in COVID-19. A distributive justice framework can gain traction in clinical decision-making guidelines and system-level reallocation of resources but will succeed only if the medical community engages in outreach, anti-racism measures, and listens to communities in need. There should be an emphasis on implementing a distributive justice framework that treats all patients equitably, accounts for historical harm, and focuses on transparency in allocation and public health decision-making. [1] APM Research Lab Staff. 2020. “The Color of Coronavirus: COVID-19 Deaths by Race and Ethnicity in the U.S.” APM Research Lab. https://www.apmresearchlab.org/covid/deaths-by-race. [2] Bharmal, N., K. P. Derose, M. Felician, and M. M. Weden. 2015. “Understanding the Upstream Social Determinants of Health.” California: RAND Corporation 1-18. https://www.rand.org/pubs/working_papers/WR1096.html. [3] Yancy, C. W. 2020. “COVID-19 and African Americans.” JAMA. 323 (19): 1891-2. https://doi.org/10.1001/jama.2020.6548; Centers for Disease Control and Prevention. 2020. “COVID-19 in Racial and Ethnic Health Disparities.” Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/community/health-equity/racial-ethnic-disparities/index.html. [4] Braveman, P., E. Arkin, T. Orleans, D. Proctor, and A. Plough. 2017. “What is Health Equity?” Robert Wood Johnson Foundation. https://www.rwjf.org/en/library/research/2017/05/what-is-health-equity-.html. [5] Bedinger, M. 2020 Apr 22. “After Uproar, Mass. Revises Guidelines on Who Gets an ICU Bed or Ventilator Amid COVID-19 Surge.” Wbur. https://www.wbur.org/commonhealth/2020/04/20/mass-guidelines-ventilator-covid-coronavirus; Wigglesworth, A. 2020 May 11. “Institutional Racism, Inequity Fuel High Minority Death Toll from Coronavirus, L.A. Officials Say.” Los Angeles Times. https://www.latimes.com/california/story/2020-05-11/institutional-racism-inequity-high-minority-death-toll-coronavirus. [6] Executive Office of Health and Human Services Department of Public Health. 2020 Oct 20. “Crises Standards of Care Planning and Guidance for the COVID-19 Pandemic.” Commonwealth of Massachusetts. https://www.mass.gov/doc/crisis-standards-of-care-planning-guidance-for-the-covid-19-pandemic. [7] Emanuel, E. J., G. Persad, R. Upshur, et al. 2020. “Fair Allocation of Scarce Medical Resources in the Time of Covid-19. New England Journal of Medicine 382: 2049-55. https://doi.org/10.1056/NEJMsb2005114. [8] Salway, S., G. Mir, D. Turner, G. T. Ellison, L. Carter, and K. Gerrish. 2016. “Obstacles to "Race Equality" in the English National Health Service: Insights from the Healthcare Commissioning Arena.” Social Science and Medicine 152: 102-110. https://doi.org/10.1016/j.socscimed.2016.01.031. [9] Rawls, J. A Theory of Justice (Revised Edition) (Cambridge, MA: Belknap Press of Harvard University Press, 1999). [10] Zack, N. Applicative Justice: A Pragmatic Empirical Approach to Racial Injustice (New York: The Rowman & Littlefield Publishing Group, 2016). [11] Charatz-Litt, C. 1992. “A Chronicle of Racism: The Effects of the White Medical Community on Black Health.” Journal of the National Medical Association 84 (8): 717-25. http://hdl.handle.net/10822/857182. [12] Washington, H. A. Medical Apartheid: The Dark History of Medical Experimentation on Black Americans from Colonial Times to the Present (New York: Doubleday, 2006). [13] d'Oliveira, A. F., S. G. Diniz, and L. B. Schraiber. 2002. “Violence Against Women in Health-care Institutions: An Emerging Problem.” Lancet. 359 (9318): 1681-5. https://doi.org/10.1016/S0140-6736(02)08592-6. [14] Hafeez, H., M. Zeshan, M. A. Tahir, N. Jahan, and S. Naveed. 2017. “Health Care Disparities Among Lesbian, Gay, Bisexual, and Transgender Youth: A Literature Review. Cureus 9 (4): e1184. https://doi.org/10.7759/cureus.1184; Drescher, J., A. Schwartz, F. Casoy, et al. 2016. “The Growing Regulation of Conversion Therapy.” Journal of Medical Regulation 102 (2): 7-12. https://doi.org/10.30770/2572-1852-102.2.7; Stroumsa, D. 2014. “The State of Transgender Health Care: Policy, Law, and Medical Frameworks.” American Journal of Public Health. 104 (3): e31-8. https://doi.org/10.2105/AJPH.2013.301789. [15] Stepanikova, I., and G. R. Oates. 2017. “Perceived Discrimination and Privilege in Health Care: The Role of Socioeconomic Status and Race.” American Journal of Preventative Medicine. 52 (1s1): S86-s94. https://doi.org/10.1016/j.amepre.2016.09.024; Swartz, K. “Health Care for the Poor: For Whom, What Care, and Whose Responsibility?” In Cancian, M., and S. Danziger (Eds.). Changing Poverty, Changing Policies (New York: Russell Sage Foundation Press, 2009), 69-74. [16] Meghani, S. H., E. Byun, and R. M. Gallagher. 2012. “Time to Take Stock: A Meta-analysis and Systematic Review of Analgesic Treatment Disparities for Pain in the United States.” Pain Medicine 13 (2): 150-74. https://doi.org/10.1111/j.1526-4637.2011.01310.x; Williams, D. R., and T. D. Rucker. 2000. “Understanding and Addressing Racial Disparities in Health Care.” Health Care Financing Review 21 (4): 75-90. https://scholar.harvard.edu/davidrwilliams/dwilliam/publications/understanding-and-addressing-racial-disparities-health. [17] Hoffman, K. M., S. Trawalter, J. R. Axt, and M. N. Oliver. 2016. “Racial Bias in Pain assessment and treatment recommendations, and false beliefs about biological Differences Between Blacks and Whites.” PNAS 113 (16): 4296-4301. https://doi.org/10.1073/pnas.1516047113. [18] Pacheco, C. M., S. M. Daley, T. Brown, M. Filipp, K. A. Greiner, and C. M. Daley. 2013. “Moving Forward: Breaking the Cycle of Mistrust Between American Indians and Researchers.” American Journal of Public Health. 103 (12): 2152-9. https://doi.org/10.2105/AJPH.2013.301480. [19] Velasco-Mondragon, E., A. Jimenez, A. G. Palladino-Davis, D. Davis, and J. A. Escamilla-Cejudo. 2016. “Hispanic Health in the USA: A Scoping Review of the Literature.” Public Health Reviews 37:31. https://doi.org/10.1186/s40985-016-0043-2. [20] Cameron, K. A., J. Song, L. M. Manheim, and D. D. Dunlop. 2010. “Gender Disparities in Health and Healthcare Use Among Older Adults.” Journal of Women’s Health (Larchmt) 19 (9): 1643-50. https://doi.org/10.1089/jwh.2009.1701. [21] Bierman, A. S. 2007. “Sex Matters: Gender Disparities in Quality and Outcomes of Care. Canadian Medical Association Journal 177 (12): 1520-1. https://doi.org/10.1503/cmaj.071541; Fowler, R. A., S. Sabur, P. Li, et al. 2007. “Sex-and Age-based Differences in the Delivery and Outcomes of Critical Care. Canadian Medical Association Journal 177 (12): 1513-9. https://doi.org/10.1503/cmaj.071112. [22] McLaughlin, D. K., and C. S. Stokes. 2002. “Income Inequality and Mortality in US Counties: Does Minority Racial Concentration Matter?” American Journal of Public Health 92 (1): 99-104. https://doi.org/.10.2105/ajph.92.1.99; Shea, S., J. Lima, A. Diez-Roux, N. W. Jorgensen, and R. L. 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