To explore the significance of neck ultrasound (NUS) combined with contrast-enhanced ultrasound (CEUS) in the diagnosis of sarcoidosis.88 patients with evidence of intrathoracic lymphadenopathy and suspected sarcoidosis with enlarged cervical lymph nodes underwent NUS, CEUS, fine-needle aspiration and core needle biopsy when technically feasible were retrospectively analyzed in this study. Seven characteristics such as enhanced mode (EM), resolution time, color Doppler flow imaging (CDFI), fading time, peaking state-uniformity, strengthen the area and symmetry were considered to perform the logistic regression model.Of 88 patients included in this study, sarcoidosis was accounted in 20 cases, tuberculosis in 23 cases, malignancy in 22 cases and inflammatory lymph node in 23 cases. There were statistically significant differences in symmetry, lymphatic hilum, homogeneity, CDFI pattern and elasticity score between the sarcoidosis and non-sarcoidosis groups via NUS. Similarly, we also acknowledged a statistically significant differences in EM, homogeneity, presence or absence of necrosis between the sarcoidosis and non-sarcoidosis groups via CEUS to further group the non-sarcoidosis into tuberculosis, malignancy or inflammatory disorder. The percentage correction of prediction was 90% (18/20).NUS combined with CEUS has characteristic features in sarcoidosis with cervical lymph node involvement, which is helpful for its diagnosis and differential diagnosis. The binary classification model of NUS combined with CEUS features can help differentiate sarcoidosis from non-sarcoidosis groups. The NUS combined with CEUS is very essential fordiagnosis of sarcoidosis from other granulomatous non-sarcoidosis lesionsnon-invasively.Sarcoidosis is a systemic disease of unknown etiology, with the pathological feature of non-caseous epithelioid granulomas. In addition to the lung and intrathoracic lymph nodes, many organs including cervical lymph node could be involved , 2. SarcAlthough great efforts have been devoted to establish methodologies that can differentiate sarcoidosis from other lung diseases –6, the dContrast-enhanced ultrasound (CEUS) is a new technique used for real-time assessment of tissue perfusion. It has been widely used to evaluate liver, kidney, pancreas, spleen, ovarian, thyroid, breast, prostate and even lung lesions in the current clinical practice –15. It hCEUS helps radiologists investigate and characterize focal lesions. Its contrast pool, sensitivity and specificity in diagnosing liver lesions are similar to contrast CT on the contrary CT is more costly and involves higher levels of ionizing radiation exposure. Recently, CEUS has often been used to identify benign and malignant superficial lymph nodes –22.Previous studies have shown that CEUS has a higher sensitivity in identifying small blood vessel reductions or areas of multiple blood vessels that cannot be detected by Doppler technology leading to a better evaluation of LNS classification .Compared with CT and MRI, gray-scale ultrasound combined with CEUS can assess the shape, margins, internal structure, and vascularization of superficial lymph nodes . It imprThe main limitation of CEUS is the practice mode, because the interpretation of ultrasound images depends on technical skills and the experience of the radiologist. In addition, CEUS is not suitable for patients who have allergic reactions to contrast agents and pregnant women.Therefore, this study intends to retrospectively analyze the CEUS qualitative diagnosis data of several groups of diseases involving cervical lymph nodes accounting factors such as the enhanced mode of ultrasound contrast agent, degree of enhancement, homogeneity, presence or absence of necrosis, arrival time, peak time, wash-out time, and so on. We aim to explore the characteristics that guide the diagnosis and differential diagnosis of sarcoidosis and provide a new non-invasive diagnostic methodology for sarcoidosis involving the cervical region.This was a retrospective observational study. The study protocols were approved by the Institutional Review Boards of Shanghai Pulmonary Hospital .Altogether 88 patients with tissue proven sarcoidosis, tuberculosis (TB), lung cancer or non-specific inflammation were evaluated at the Shanghai Pulmonary Hospital between September 2018 and December 2019 were recruited for this study. All these patients manifested cervical lymphadenopathy and pathological diagnosis of their lymph node were consistent with their clinical diagnosis. The diagnosis of sarcoidosis was established based on the presence of clinical symptoms, radiological features compatible with sarcoidosis, and biopsy evidence of noncaseating epithelioid cell granulomas with other known causes of granulomatosis excluded.All of conventional ultrasound scans and CEUS examinations were performed by two senior clinical ultrasonographers with more than 3 years of experience in neck ultrasound (SMJ and WY). Conventional ultrasound scans were performed by a 6–15 MHZ probe . A routine ultrasonography on the target lesion was performed by adjusting the focus and depth of the lesion, then selecting the best acoustic window to fully display the lesion boundary and finally evaluating the symmetry of the lymph nodes , number (1 or > 1), longitudinal meridian (≥ 10 mm or < 10 mm), aspect ratio (< 2 or ≥ 2), lymphatic hilum (present or absent), border (clear or unclear), echo (hypoechoic or hyperechoic), homogeneity (uniform or non-uniform), calcification (present or absent), and fusion (present or absent). Color Doppler flow imaging (CDFI) and elastic imaging were performed after gray-scale ultrasound. The CDFI pattern of lymph nodes can be divided into four types: portal, dendritic, annular and others. The elasticity scoring was performed based on the elastography 5 points proposed by Itoh et al. . The casAfter conventional ultrasound, the largest diameter nodule was selected before switching to CEUS mode. CEUS was performed by a 3–9 MHZ probe , and using a low mechanical index (MI < 0.13). The contrast agent  was injected intravenously through the anterior cubital vein with a dose of 1.5 ml followed by bolus irrigation with 5 ml normal saline. The timer was started while injecting the contrast agent, followed by 3 min continuous observation and recording of data. It was also made sure that the image and condition settings remained unchanged during the entire imaging process. We observed and recorded the following indicators: the enhanced mode of ultrasound contrast agent , degree of enhancement , homogeneity (uniform or non-uniform), necrosis (present or absent), and arrival time of contrast agent, peak time, and wash-out time.Abnormal lymph nodes were defined based on a short axis diameter of ≥ 6 mm. When technically feasible, FNA of lymph nodes was performed by a trained physician. If suitable, a core needle biopsy (CNB) was performed on the lymph node using a 18G*10 cm biopsy needle . On site cytology was not performed. The presence of noncaseating granulomas with negative stains for mycobacteria and fungi was considered diagnostic of sarcoidosis.p < 0.05 indicated statistically significant. Two classification analysis was performed by R software.All data were analyzed using the statistical analysis software SPSS 20.0. Continuous variables were presented as mean ± standard deviation (SD) and were compared using t-test. Chi-square test was used for analysing the categorical variables. Independent-samples t-test assuming equal variance and ANOVA were performed with p > 0.05) as shown in Table Eighty-eight patients were included in this study with 20 cases of sarcoidosis, 23 cases of tuberculosis, 22 cases of malignancy and inflammatory lymph nodes in 23 cases. There was no significant difference in age and sex between the sarcoidosis group and the tuberculosis group (p < 0.05). Furthermore, specific to sarcoidosis and tuberculosis, there were statistical differences (p < 0.05) in symmetry, homogeneity, border, fusion and CDFI pattern (dendritic type was more common in the sarcoidosis group). While comparing sarcoidosis and malignancy group, there were statistically significant variation in symmetry and CDFI pattern . While comparing sarcoidosis with the inflammatory group, there were statistically significant differences (p < 0.05) in symmetry, longitudinal meridian, lymphatic hilum, CDFI pattern  and elasticity score.Table p < 0.05).The distribution of sarcoidosis was discovered to be more bilateral when compared with non-sarcoidosis groups . 100% of sarcoidosis lesion showed no lymphatic hilum, which was significantly different from inflammatory group  Fig. 0, 85% FiWhile considering the homogeneity, the perfusion in both sarcoidosis group and inflammation group were 100% uniform. While mainly the perfusion of tuberculosis lymph nodes were found to be non-uniform. Similarly, while regarding the necrosis, sarcoidosis lesions were 100% without any necrosis. 19/23 (82.6%) in tuberculosis and 12/22 (54.5%) in malignancy group showed necrosis.The seven characteristics were finally entered into the two classification analysis model which included enhancement mode (EM), resolution time (RT), CDFI, fading time (FT), peaking state-uniformity (PTSU), strengthen the area (STA) and symmetry. The percentage correction of prediction was 90% (18/20) Fig. .Fig. 3A Sarcoidosis is a systemic disease in which intrathoracic lymph nodes, lungs and cervical lymph nodes are also commonly involved. The application value of neck ultrasound in sarcoidosis is worth exploring. Comparing with non-sarcoidosis groups, the characteristic ultrasound imaging features of sarcoidosis include: symmetry, non-existence of lymphatics, uniformity, and dendritic CDFI pattern are more common with elasticity score ≥ 3. The characteristic CEUS imaging features of sarcoidosis include: multi-center filling, uniform lesion and absence of necrosis.Sarcoidosis can affect almost any organ. Bilateral hilar lymphadenopathy is its characteristic manifestation often accompanied by peripheral lymph node involvement. In our study, 90.0% (18/20) of bilateral cervical lymph nodes were symmetrically enlarged in the sarcoidosis group, and were comparable to non-sarcoidosis groups which included the tuberculosis group, tumor group, and inflammation group demonstrating highly significant statistical differences.Normal lymphatic portal structure is formed by lymph nodes’ arteriovenous structure, fat and lymph sinus located in the central part of the lymph node. Schmid-Bindert G et al. considered that the disappearance of the lymphatic portal structure is one of the ultrasound features to identify benign and malignant lymph nodes . HoweverIn our study, there were 20 cases of sarcoidosis and NUS did not find lymphatic hilum which was significantly different from non-sarcoidosis group. Lymph node enlargement in the inflammation group was reactive hyperplasia and the structure of the lymphatic gate was not obliterated. Theoretically, structure of the lymphatic hilum should be intact in all the cases, but in 30.4% (7/23) of the cases, lymph nodes in the inflammation group of this study lymphatic hilum was not visible which is consistent with previous studies. According to Dudau et al., the reactive hyperplasia of lymph nodes in the cancer drainage area can be easily confused with metastatic lymph nodes .In terms of ultrasound contrast agent filling methods, our results showed that the sarcoidosis group was mainly multicenter , and the tuberculosis group and tumor group were mainly centripetal  whereas the inflammation group was mainly eccentric . Histologically, sarcoidosis was characterized by non-caseating granuloma. Within the affected lymph nodes, the usual structure was obscured by multiple distinct, "tight" and discrete granulomas . The typIn terms of the uniformity of enhancement, both the sarcoidosis group and the inflammatory nodules group showed uniform enhancement, while the tuberculosis group and the tumor group showed an uneven enhancement. The reason might be because the tuberculosis group is prone to have caseous necrosis of the lymph nodes. Likewise, for tumor group, tumor cells block the blood vessels or hypercoagulable blood leads to thrombosis.Necrosis is more common in tuberculosis and tumors. In general, sarcoidosis is not a condition to consider necrosis initially as most sarcoid granulomas are not accompanied by necrosis. Although there are individual sarcoidosis-like necrotizing granulomas reported in the previous literature. Ultrasound contrast agent is a blood pool imaging agent, which can accurately reflect the microcirculation blood perfusion inside the lesion and help distinguish the necrotic area within the lesion .This study preliminarily explored the application of NUS and CEUS in the diagnosis of sarcoidosis. They can reflect partial vascularization forming a different impression of pseudo-ischemic area which can more truly reflect the active ingredients in the lesion. In our study, 20 target lymph nodes in the sarcoidosis group showed uniform enhancement during CEUS and no non-enhanced area indicated that there was no necrosis. Therefore, necrosis found through CEUS can be used to rule out sarcoidosis for differential diagnosis.This study has the following limitations: (1) this study is a retrospective study of a single center and it is difficult to avoid the small number of cases and the deviation of the disease, (2) the prospective verification has not been performed to evaluate its diagnostic efficacy, (3) the authors didn’t combine the quantitative parameters obtained by CEUS time-intensity curve analysis to obtain more valuable diagnostic results. In future, a more reasonable multicenter prospective cohort study can be established to further verify the value of NUS combined with CEUS in the diagnosis of patients with sarcoidosis involving cervical lymph nodes to obtain a better result.In summary, sarcoid lymph nodes displayed under conventional ultrasound and CEUS have certain specific characteristics which are helpful for the diagnosis and differential diagnosis of sarcoidosis and have a great potential to become an important non-invasive complement to existing diagnostic methods. The ultrasound diagnosis model established by the binary classification algorithm helps to distinguish the diagnosis of sarcoidosis from other granulomatous non-sarcoidosis lesions such as malignancy, tuberculosis and inflammatory lymph nodes.


The excessive use of antibiotics has contributed to the rise in antibiotic-resistant bacteria, and thus, new antibacterial compounds must be developed. Composite materials based on graphene and its derivatives doped with metallic and metallic oxide nanoparticles, particularly Ag, Cu, and Cu oxides, hold great promise. These materials are often modified with polyethylene glycol (PEG) to improve their pharmacokinetic behavior and their solubility in biological media. In this work, we performed molecular dynamics (MD) simulations to study the interaction between small Ag, Cu, and CuO clusters and several graphene-based materials. These materials include pristine graphene (PG) and pristine graphene nanoplatelets (PGN) as well as PEGylated graphene oxide (GO_PEG) and PEGylated graphene oxide nanoplatelets (GO-PEG_N). We calculated the adsorption energies, mean equilibrium distances between the nanoparticles and graphene surfaces, and mean square displacement (MSD) of the nanoclusters. The results show that PEGylation favors the adsorption of the clusters on the graphene surfaces, causing an increase in adsorption energies and a decrease in both distances and MSD values. The strengthening of the interaction could be crucial to obtain effective antibacterial compounds. E. coli bacteria. Many subsequent studies showed that pristine graphene, GO, and rGO have all antibacterial activity [The excessive use of antibiotics has contributed to the rise in antibiotic-resistant bacteria, and new antibacterial compounds must be developed. Graphene is a 2D monolayer material with long edges and large accessible surfaces, which give it an excellent ability to immobilize diverse molecules including nanoparticles or drugs. Hu et al.  first reactivity ,6,7,8,9.activity ,14,15,16activity ,23,24,25activity . The polactivity ,28. For activity  and showactivity  and biocactivity ,32.Molecular dynamics (MD) simulations allow the study of materials from a molecular viewpoint, providing information on an atomic scale usually inaccessible to experimental techniques . The intIn this work, we carried out MD simulations of the adsorption of small Ag, Cu, and CuO clusters on pristine graphene monolayers (PG), PG nanoplatelets (PGN), PEGylated graphene oxide monolayers (GO_PEG), and PEGylated graphene oxide nanoplatelets (GO-PEG_N). The work focuses on a comparison of the behavior of these three nanoclusters interacting with the above-mentioned graphene-based materials and allows completing our previous results on Ag and Cu nanoclusters interacting with a graphene surface . In our . [MD simulations were done with the Forcite module of the Materials Studio 9 software  in the N. ,54. Elecn = 10). In the interest of saving computational time, only two layers of graphene were used to model the nanoplatelets. In the PEGylated nanoplatelets, both layers had the same grafting density, i.e., the number of PEG chains attached to the edges of the individual GO layers. In these starting structures, the mean final distances between the basal planes of graphene were 3.7 and 6.9 Å for PGN and GO-PEG_N, respectively. The clusters used to represent the metal nanoparticles were composed of thirteen atoms arranged in an icosahedral shape. This number was chosen because of the well-known stability of this regular icosahedron geometry for Cu and Ag nanoclusters [6O6 cluster consisting of two hexagonal layers, one above the other, was chosen. This structure was found to be stable by a density functional theory calculation [The starting configurations used for the production trajectories are shown in clusters ,56. For culation . No consGBM+cluster is the mean equilibrium potential energy of the graphene-based material  interacting with the cluster, and EGBM and Ecluster are the mean equilibrium potential energies of the isolated graphene-based materials and clusters, respectively . As the energy values are negative, the more negative the adsorption energy is, the stronger the interaction. Previous studies have shown that this adsorption energy could be a good estimate of the binding strengths of adsorbate–adsorbent systems [The adsorption energy of the clusters on the surface was calculated from the following equation: systems .i(0) is the reference position of the cluster, ri(t) is its position at time t, and N is the number of atoms of the cluster. Thus, MSD was calculated from the particle positions obtained from the trajectory using a time step of 5 ps.The mean square displacement (MSD) of the clusters, which measures the spatial extent of clusters random motion, was calculated from their positions over simulation length according to:α is the generalized diffusion coefficient and α is the diffusion exponent [MSD can be related to time through the following equation:exponent ,60. The The adsorption energy values calculated from Equation (1) are presented in 6O6 cluster is the most attracted by the surface and the Cu13 cluster is the least attracted. Ag13 lies in between. The introduction of PEG chains favors the adsorption process, increasing the adsorption energy. In addition, the nanoplatelets seem to increase the adsorption energy in all cases. This last trend should be confirmed by increasing the number of layers of the nanoplatelets in future studies.From the values listed in Here, we must note the qualitative nature of these results. It is well known that cluster geometry and size influence their adsorption energy and reactivity on graphene surfaces, and several authors have shown that quantum mechanical calculations are needed to fully understand and quantify this kind of interaction . Even wh6O6 interacts strongly with both pristine and functionalized surfaces, although the adsorption process is improved by the presence of PEG chains, as already observed for Cu and Ag clusters. We think the atomic charges of the cluster increase the electrostatic attraction between the cluster and surface, although the exact nature of the interaction should be verified by more accurate quantum mechanical calculations. Sun et al. [Cun et al.  determinn et al.  preparedn et al.  calculatEven if the calculation method used in this work cannot describe the formation of chemical bonds between the cluster and the graphene surfaces, the results obtained agree with those obtained from more accurate quantum chemical calculations.The mean equilibrium distances between the cluster and nearest surface atoms are shown in The distances shown in 6O6 cluster, the plots corresponding to the Cu atom (shown in red) are slight shifted to larger values, which is in accordance with the results shown in The radial distribution functions (RDF) of clusters and graphene-based surfaces are shown in Although a detailed analysis of the mechanisms of cluster diffusion is beyond the scope of this work, we think that the MSD of the cluster center of mass can help shed more light on the differences observed in adsorption energies. Total MSD is plotted versus simulation length in 13 and Ag13 clusters interacting with the pristine materials present the highest MSD values. Both PG and PGN weakly attract both clusters, which keep constantly moving over the material surface. However, the functionalization of the graphene layers drastically reduces their mobility  in both the pristine and functionalized materials.CuTo show more clearly the cluster movement, the diffusion trajectories of the cluster center of mass over the graphene surface during the last 250 ps of simulation length for both PG and PGN are displayed in xx and MSDyy components have non-zero values due to the movement of the cluster over the surface and parallel to it during the whole simulation length. In the functionalized structures, the cluster may carry out slight movements between or along PEG chains  would enable to address in more detail the equilibrium configurations of the structures, as well as the energetic affinity between the clusters and the graphene-based surfaces. Although these more demanding simulations allows gain a deeper insight into the mechanisms that control the interaction between graphene-based materials and nanoparticles, we think our MD results can provide useful qualitative information and allow handling a larger number of atoms in shorter computational times  were needed for systems containing 3389 atoms). In future work, DFT calculations will be done to validate these results and be able to consider our molecular dynamics simulations as a quicker reliable method to handle these kinds of systems. Another important aspect that should be considered is the use of a solvent in the calculations. The inclusion of water may have severe effects to several important parameters, such as the equilibrium configurations of the surfaces, the spatial arrangement and the dynamics of the metallic clusters, as well as the energetic affinity between the clusters and the surfaces. Thus, future simulations must include solvent to get a more realistic analysis of real systems.MD simulations were carried out to study the interaction between Cu


Three interfacial structures including graphene–Al2O3, graphene–Al2OC and graphene-WC were determined in the Al2O3–WC–TiC–graphene composite by TEM. The interfacial adhesion energy and interfacial shear strength were calculated by first principles, and it has been found that the interfacial adhesion energy and interfacial shear strength of the graphene–Al2OC interface  were far lower than those of graphene–Al2O3  and graphene–WC  interfaces. Thus, the composite with the strong and weak hybrid interfaces was successfully obtained, which was further confirmed by the microstructural analysis. This interfacial structure could induce strengthening mechanisms such as load transfer, grain refinement, etc., and toughening mechanisms such as crack bridging, graphene pull-out, etc., which effectively improved mechanical properties.The interfacial structures and interfacial bonding characteristics between graphene and matrix in graphene-reinforced Al Cheng et al. [2O3/TiC ceramic composites, and they found that the optimal fracture toughness (8.7 ± 0.4 MPa·m1/2) was obtained when the content of GPLs was 0.2 wt%, which increased by 67.3% compared to the Al2O3/TiC ceramic. Wang et al. [2O3/WC/TiC/graphene ceramic composites, and they found that the optimal flexural strength and fracture toughness were 646.31 ± 20.78 MPa, 9.42 ± 0.40 MPa·m1/2, respectively, when the content of graphene was 0.5 vol%, which were significantly improved compared to the composite without graphene.Graphene has been proven to be an ideal reinforcement to fabricate Aloperties ,2. Grigorength 90 ± 56 MPa2–SiC matrix composite ceramics by incorporating graphene, and they found that the interfaces could induce multiple toughening mechanisms including crack deflection, microcracks, graphene bridging and pull-out. Bódis et al. [3N4–MLG interfaces improved the fracture toughness of Si3N4–MLG composites; however, excessive nanopores led to a lower fracture toughness. Composites with strong and weak bonding interfaces simultaneously can induce microcracks at the interfaces, thus improving strength and toughness [Interfaces of graphene-reinforced composites are of great significance to their performances . The strs et al.  found thoughness ,12. Sun oughness  found th2O3 interfacial phase at the interface between Al and graphene effectively improved the interfacial bonding strength of the Al–graphene interface, which further improved mechanical properties of composites. Chu et al. [7C3 at the CuCr–RGO interface, which improved interfacial bonding strength. However, in the field of graphene-reinforced Al2O3–WC matrix ceramics, interfacial phases and interfacial bonding characteristics between graphene and matrix grains have not been explored. Furthermore, the relationship among interfacial structure, mechanical properties and strengthening and toughening mechanisms in Al2O3–WC matrix ceramic composites also needs to be further understood.The formation of strong and weak hybrid interfaces mainly depends on regulating interfacial bonding strength. And formation of interfacial phases induced by interfacial chemistry reactions is an effective method to regulate interfacial bonding strength. Ju et al.  found thu et al.  found thx) by DFT simulations during synthetic growth with CmSn , and they successfully predicted the range of S concentrations appropriate for well-structured FL–CSx. From the above description, it can be concluded that DFT methods can provide significant help to analyze interfacial structures and other features of composites at the atomic level. However, in the field of Al2O3–WC matrix ceramic composites, the related reports are few.In order to more thoroughly investigate interfacial bonding characteristics, some theories such as density functional theory (DFT) were more widely used in the interfacial investigation of composites. Zhang et al.  studied 1) with short dwell time or without dwell time, which is beneficial to obtain a critical relative density and makes pores unstable [2) with long dwell time; during this stage, grain boundary migration is frozen whereas grain boundary diffusion is active, which is beneficial to inhibiting grain growth while promoting densification [2O3 ceramics, and they found that a measurably higher final density, a smaller average grain size and a narrower distribution in grain sizes were achieved with the two-step sintering technique.Two-step sintering is reckoned as an effective method to produce ceramic composites, because this sintering method can suppress ceramic grain growth while fully densifying ceramic composites ,17. In tunstable . In the fication . In addification  respecti2O3–WC–TiC and Al2O3–WC–TiC–graphene composites were prepared by two-step hot pressing sintering, and the microstructures and mechanical properties of the two composites were evaluated. Especially, the interfacial structures were analyzed by TEM, and the interfacial adhesion energy and interfacial shear strength of Al2O3–graphene, Al2OC–graphene and WC–graphene were calculated by first principles. In addition, the strengthening and toughening effects in ceramic composites induced by the strong and weak hybrid interfaces were discussed.In this work, the Al2/g, purity: 99%, XFNANO Materials Technology Co., Ltd., Nanjing, China) was dispersed for 1 h in this dispersion. Polyethylene glycol  was used as dispersion media to disperse nanosized TiC powders. TiC  powders were first dispersed in the absolute ethyl alcohol for 10 min, and then PEG was added into the TiC slurry, and the slurry was further dispersed for 20 min. The dispersed graphene slurry and TiC slurry were mixed, and Al2O3 powders , WC powders , MgO powders , Y2O3 powders  and Co powders  were added into the mixed slurry. The mixed slurry was dispersed for 1 h to get stable hybrid slurry. It is important to point out that the Al2O3, WC, TiC, MgO, Y2O3 and Co powders were all provided by Chaowei Nanotechnology Co., Ltd., Shanghai, China. It is also important to point out that MgO and Y2O3 were used as sintering aids and Co was used as metal binder. After dispersion, wetting ball milling and vacuum drying were conducted on the hybrid slurry to get composite powders. Then, the composite powders were screened using a 200-mesh sieve.Polyvinyl pyrrolidone  was chosen as dispersion medium to disperse graphene. PVP powders were firstly dispersed in the absolute ethyl alcohol for 1 h to get stable graphene dispersion. After that, graphene  furnace . Firstly, the composite powders were heated to 1750 °C at a heating rate of 40 °C/min without dwell, and then they were rapidly cooled to 1600 °C for 15 min dwell time; finally, they were cooled to the room temperature. It is important to point out that the 1600 °C dwell temperature is determined according to our previous report in literature , becauseE is the Young’s modulus of composites, H is the indentation hardness, P is the indentation load, and c is the half length of indentation crack. At least 10 indentations were performed on each composite during the indentation experiment.After cutting, grinding and polishing, dimensions of the test specimens were 3 mm × 4 mm × 30 mm. The bulk density of specimens was obtained by Archimedes method and the theoretical density was calculated by the mixing rule. The average grain size of specimens was obtained by the linear intercept method, and at least 5 SEM images and 300 ceramic grains were included for each specimen. Flexural strength was measured by three-point bending method operated on an electromechanical universal testing machine  Co., Ltd., Shenzhen, China), and the span and loading velocity were 20 mm and 0.5 mm/min, respectively. At least five specimens were tested for each composite during the three-point bending experiment. Vickers hardness was obtained by a Vickers hardness tester . The load and dwell time were 20 kg and 15 s, respectively. Fracture toughness of specimens was obtained by the indentation method, its value was calculated by the following equation :(1)KIC=0Phase compositions of specimens were analyzed by the Rigaku Ultima IV X-ray diffraction  device. The graphene structures were examined by a HORIBA LabRAM HR Evolution Raman spectroscopy . Microstructures of specimens were observed by a JEOL JSM-7610F field emission scanning electron microscopy  and a ZEISS Gemini 300 FE-SEM . Interfacial structures were analyzed by a FEI Talos F200 transmission electron microscopy  and a Talos F200X G2 TEM .2O3, WC and TiC are detected in the two composites, however, graphene is not detected in AWTG0.5, which may be related to the low volume fraction of graphene. D/IG), and a higher ID/IG value denotes the higher structure defect [D/IG value of AWTG0.5 is slightly lower than that of staring graphene, which indicates that a slight agglomeration occurs during the dispersing or ball milling process, decreasing the edge defects of graphene [e defect ,23. As sgraphene .2O3, WC, C and graphene, respectively. The C solid solution may result from a part of W atoms dissolving into TiC lattices during sintering process. Meanwhile, the free carbon is left, which can be found in XRD patterns shown in 2O3 matrix. In addition, some dislocations near intragranular grains can be clearly observed. It has been reported that the intragranular structure and accumulation of dislocations are beneficial to improving the mechanical properties of ceramic composites [mposites ,28,29.The interfacial structure between WC and graphene is shown in 2O3 and graphene are shown in 2O3 and the interfaces are free from grooves, pores and gaps. Furthermore, the interfaces between Al2O3 and graphene show different interfacial characteristics. The interface shown in 2O3 and graphene without interfacial chemical compounds. However, as shown in 2O3. 2OC. The formation of Al2OC can be attributed to the following chemical reactions [2O3 grains in the presence of graphene undergo a carbothermal reduction to form gaseous Al2O which further reacts with residual carbon to form Al2OC.The interfacial structures between Aleactions ,31:Al2O32O3-WC-TiC-graphene ceramic composite using traditional HP sintering technology at 1700 °C for 10 min dwell time, and we found that interfacial phases of Al4O4C and Al4C3 were formed between graphene and Al2O3. Comparing the present work and the previous work in reference [2OC at the interface between graphene and Al2O3, however, a higher dwell temperature was beneficial to producing Al4O4C and Al4C3, which is in agreement with our research results.In our previous work , we prepeference , it can eference  that a l2OC, graphene–Al2O3 and graphene–WC interfaces are shown in 3, 9.73 × 9.73 × 20.93 Å3 and 6.62 × 6.62 × 19.46 Å3, respectively. After geometry optimization, the equilibrium distances between the graphene and the top of the Al2OC surface, the graphene and the top of the Al2O3 surface and the graphene and the top of the WC surface are 2.08 Å, 1.78 Å and 1.84 Å, respectively. A 15 Å vacuum layer is used in every calculation model to prevent interactions between the periodic layers [The interfacial bonding characteristics between graphene and matrix grains were further analyzed by first-principles calculations based on density functional theory (DFT). The calculations were performed by VASP and the detailed calculation method is depicted in our previous report . It is ic layers .Egraphen/matrix is the total energy of interfacial structure, Egraphene and Ematrix are the surface energy of graphene and matrix, A is the area of the interface. In order to calculate the interfacial shear strength, the conjugate gradient optimization method was used to relax the atomic positions by keeping the cell size fixed. With the increase of shear displacement, the shear stress increased until it reached a maximum value, and the shear strength was calculated at the maximum shear value. The calculated results of the adhesion energy and interfacial shear strength of graphene–Al2OC, graphene–WC and graphene–Al2O3 interfaces are shown in 2O3 and graphene–WC were reported in our previous work [2) and interfacial shear strength (59.32 MPa) of the graphene–Al2OC interface are much lower than those of graphene–WC and graphene–Al2O3 interfaces, which indicates that the weak chemical bonding is generated at the graphene–Al2OC interface and the load transfer efficiency will be affected. However, the high adhesion energy of graphene–WC (0.781 eV/nm2) and graphene–Al2O3 (0.967 eV/nm2) interfaces indicates the strong bonding interfaces are generated in the composite. Furthermore, the high interfacial shear strength of graphene–WC (229.84 MPa) and graphene–Al2O3 (395.77 MPa) interfaces is beneficial to improving load transfer efficiency, further improving mechanical properties of AWTG0.5 [2OC, graphene–WC and graphene–Al2O3 interfaces indicates that the composite with the strong and weak hybrid interfaces is successfully obtained.The adhesion energy was calculated by the following equation :(2)Wad=(ous work . It can  AWTG0.5 . The forρ) can be used to analyze interfacial bonding characteristics by charge interaction, and it can be calculated by the following equation [ρAB, ρA and ρB denote the charge density of AB hybrid system, isolated A system and isolated B system, respectively. After geometry optimization and calculation, the 3D charge density differences for graphene–Al2OC, graphene–WC and graphene–Al2O3 interfaces with the isovalue of 0.003 e/Å3 are shown in 2OC interface is characterized by the covalent bonding [2O3 surface, therefore, we can guess that graphene may change electron distribution of Al2O3 surface when the graphene and Al2O3 interfaces are in contact, which promotes the interaction between graphene and Al2O3. In addition, as shown in 2O3 interfaces is obviously higher than that of graphene-Al2OC, which indicates that the charge interaction of the graphene–WC and graphene–Al2O3 interfaces is stronger than that of the graphene–Al2OC interface, and further indicating that the two interfaces possess the higher interfacial bonding strength [The charge density difference (Δequation :(3)Δρ=ρA bonding . As show bonding . As showstrength .2O3 and WC in AWTG0; it can be seen that a clear groove is distributed along the interface and the groove can greatly weaken the interfacial bonding strength, which further demonstrates that the interfaces in AWTG0 are characterized by weak bonding. The mixed fracture mode of intergranular fracture and transgranular fracture in AWTG0.5 indicates that the strong and weak hybrid interfaces are formed in the composite, which is consistent with the conclusion drawn by the first-principles calculations. 2O3 and WC in AWTG0.5; it can be seen that the Al2O3 grain and WC grain are physically and tightly bonded without interfacial phases. The different interfacial bonding characteristics between Al2O3 and WC in AWTG0 and AWTG0.5 can be attributed to the introduction of graphene in ATWG0.5, which improves the grain boundary diffusion by improving the distribution of current and heat in the composite [2O3.omposite . In addiomposite ,40. Ther2O3–WC–TiC–graphene ceramic composite comparing the traditional HP sintering technology.The mechanical properties of AWTG0 and AWTG0.5 are shown in R) of graphene in composites can be calculated by the following equation [σc is the strength of the composite, σm is the strength of the matrix, Vgraphene is the volume fraction of graphene. According to Equation (4), the R value of AWTG0.5 can be determined as 135.18. This R value is relatively higher compared to the previous reports in graphene reinforced Al2O3-based ceramic composites [The strengthening efficiency (equation :(4)R=σc−mposites ,44,45, w2O3 interfaces possess high interfacial shear strength, which further improves the load transfer capability of AWTG0.5.Generally, the load transfer strengthening is considered to be a main strengthening mechanism in graphene reinforced composites ,47,48. Adc and dm are the average grain sizes of the composite with graphene and the composite without graphene, respectively. As shown in According to the Hall–Petch relation, grain refinement can effectively improve the strength of composites. The improved strength contributed by the grain refinement can be calculated by the following equation :(5)ΔσGr=E is the Young’s modulus of the composite, r is the radius of graphene, l is the length of pulled out graphene, iτ is the friction of debonding interface, A is the area fraction of pulled out graphene. As a 2D nanomaterial, graphene possesses high specific surface area, the A value is much higher than other reinforcements. In addition, as shown in 2O3–WC–TiC–graphene composite was prepared by two-step hot pressing. The interfacial characteristics, mechanical properties as well as strengthening and toughening mechanisms were systematically investigated. The relationships among them were also analyzed.The staggered distribution of strong and weak hybrid interfaces in ceramic composites is beneficial to improving the strength and toughness of ceramic materials. When graphene is incorporated into ceramic composites, depending on its unique 2D structure and large specific surface area, it can contact with different ceramic grains to create a lot of interfaces and facilitate the formation of strong-weak hybrid interfaces. Based on this material design philosophy, the Al2O3, graphene–Al2OC and graphene–WC could be found in the Al2O3–WC–TiC–graphene composite by TEM. First-principles calculations were performed to investigate interfacial bonding strength. It was found that the adhesion energy and interfacial shear strength of the graphene–Al2OC interface were 0.287 eV/nm2 and 59.32 MPa, respectively, indicating the bonding interface was weak. However, the high adhesion and interfacial shear strength of the graphene–Al2O3  and graphene–WC  interfaces indicated that the strong bonding interface was formed in the ceramic composite. Thus, the composite with the strong and weak hybrid interfaces was successfully fabricated. The microstructure analysis further demonstrated the formation of the strong and weak hybrid interfaces.Three different bonding interfaces including graphene–Al2O3–WC–TiC–graphene composite were significantly improved compared to the Al2O3–WC–TiC composite.The strong and weak hybrid interfaces could induce strengthening mechanisms such as load transfer, grain refinement, etc., and toughening mechanisms such as crack bridging and graphene pull-out, etc. Therefore, mechanical properties of the Al2O3-based ceramic composites.This work can provide a method basis for the research on the interfacial structures and interfacial bonding strength of other ceramic matrix composites. Comparing the research results in this work and reference , it can


Israel’s containment of the first wave of Covid-19 was relatively successful. Soon afterwards, however, in the summer months, a harsher pandemic wave developed, resulting in many more seriously ill and dead Israelis. Israel was the world’s first country to impose a second general lockdown. The present study outlines the early months of Israel’s second pandemic wave, until the imposition of the second general lockdown, and their impact on various communities. The investigation is conducted in conjunction with five sociodemographic variables: population density, socioeconomic status, rate of elderly population, minority status (Jewish / Arab identity) and religiosity (Ultra-Orthodox vs. other Jewish communities).The analysis is based on a cross sectional study of morbidity rates, investigated on a residential community basis. Following the descriptive statistics, we move on to present a multivariate analysis to explore associations between the five aforementioned sociodemographic variables and Covid-19 morbidity in Israel in the early second pandemic wave vs. the first Covid-19 outbreak.Both the descriptive statistics and regressions show morbidity rates to be significantly and positively associated with communities’ population density and significantly and negatively associated with socioeconomic status (SES) and the size of elderly population. These results differ from Wave I morbidity, which was not significantly associated with SES. Another difference vis-a-vis Wave I is the rise of morbidity in Arab communities that led to the disappearance of the previously observed significant negative association of morbidity with minority (Arab) status. Exceptional morbidity was found in Ultra-Orthodox Jewish communities.The second wave of Covid-19 in Israel has profoundly affected marginalized communities characterized by high residential density, low SES and minority status. Other marginalized and disempowered communities have also been badly hit. While acknowledging the potential contribution of various possible causes, we highlight the policy response of Israel’s government during the early weeks of the second Covid-19 outbreak, suggesting that the severe second wave might possibly be associated with belated, undecided government response during this period. Israel’s first case of SARS-CoV-2, hereafter referred to as Covid-19, was diagnosed in February 27, 2020. On March 16, with roughly 60 new confirmed cases a day, a general statewide lockdown was declared. The first wave climaxed in early April 2020, with 500–700 new confirmed cases a day and a total of less than 10,000 active cases. Mask wearing in public became obligatory on April 12th, but was officially enforced, though to a limited extent, only a couple of months later. From mid-April, the Covid-19 morbidity started to decline and lockdown restrictions were relaxed. In early June 2020, Israel had roughly 2000 active cases and a death toll of less than 300 persons, representing 33 deaths per million and a fatality rate of 1.67%, substantially lower than in most West European countries and well below the world average of 6.15% at the time.However, in June 2020, the number of new confirmed cases of Covid-19 started to rise, reaching 4000–6000 new cases a day in mid September. The number of deaths approached 1200 or 130 deaths per million. At this point, with a total of roughly 180,000 confirmed cases, 50,000 of which were active, Israel has become the world’s most infected country per population. Whereas severely affected countries like the U.S., India, Spain and France had, at that time, 43, 39, 22 and 10 seriously ill persons per million, respectively, and countries that contained the virus more successfully, like Germany, Sweden and Norway had 3, 1 and 0.2 seriously ill patients per million respectively, Israel had 61. From being one of the most successful countries to have contained the pandemic in its initial outbreak, Israel became the world’s worst affected country. In September 13, 2020, the government applied a second countrywide lockdown. Israel became the world’s first country to impose a second general lockdown.In this paper, we look into the pandemic burden through a sociodeographic lens: who were the virus new carriers, namely which communities paid the highest toll of the soaring contagion? How was the morbidity in early wave II associated with communities’ sociodemographic characteristics? For the sake of clarity, we refer to the period from the pandemic onset in late February to June 2, 2020 as ‘Wave I’ (WI) and to the subsequent period, from June 3 to the second lockdown in September 13 as ‘Early Wave II’ (EWII). Another terminological note refers to the term ‘morbidity’. As is well known, many people confirmed as Covid-19 carriers are asymptomatic. The use of the term ‘morbidity’ may, therefore, be contested. We acknowledge this ambiguity but, for the sake of reading fluency, continue to use the term ‘morbidity’ as representative of the number of confirmed cases.Morbidity rates were significantly and positively associated with population density.In the Jewish sector, morbidity rates were significantly and negatively associated with SES and percentage of elderly population.In the Arab sector, SES and percentage of elderly population were not significantly associated with morbidity.Arab communities, despite their minority status and low SES, sustained significantly lower morbidity than Jewish communities did.Our analysis of the spread of morbidity is conducted on a residential community basis. Within this fraemwork, we investigate the association of morbidity rates with five sociodemographic variables: population density, socioeconomic status (SES), percentage of elderly, minority status (Jewish/Arab descent) and religiosity. As such, this paper is a sequel of our previous analysis of these associations in Israel’s first wave of Covid-19 [This paper is a cross-sectional study, investigating rates of morbidity in Israel on a residential community basis. The analysis of Early Wave II figures was conducted in a similar format to that of Wave I: The dependent variable is Israel’s cumulative Covid-19 morbidity in EWII, spanning from June 3 to September 13, when a second lockdown was declared. Notably, this period does not fully capture the second wave, which lasted well into October, but rather, the weeks and months that led up to the second general lockdown. The numbers of confirmed Covid-19 cases are presented per community and per 1000 local community residents. Though the morbidity figures heavily depend on the scope of testing, the official daily morbidity count served as a foundational indicator of local disease spread. As such, it was consistently presented as formative of government decisions and policy.The sociodemographic variables we explore are those we have used to analyze WI morbidity: community population density, SES, percentage of elderly population and minority status. In addition, in order to refine the results, we subdivided the Jewish sector, distinguishing ultra-orthodox (UO) communities from other Jewish Israelis. Data was retrieved from Israel’s Ministry of Health Website, which presents daily cumulative morbidity figures.To supplement this data, we retrieved, for each community, figures from Israel’s Central Bureau of Statistics (CBS), depicting the following variables: community’s population density (number of residents/ community’s area of jurisdiction)‘marginal effect’ of each of the study’s variables on local morbidity rates according to the localities’ level of religiosity.Data is presented in two stages. First, descriptive statistics outline the distribution and average figures of the research variables, with a comparison between the two pandemic waves, so as to depict the difference in crude figures. In the second section, a multivariate analysis is carried out in order to assess the association between each variable and a community’s Covid-19 morbidity and to outline these relationships in Israel’s population in the two pandemic waves. Additionally, the regression data about the Jewish sector is used in order to estimate the The statistical analysis is based on the number of aggregate confirmed cases as of September 13, 2020, minus those published on June 2, 2020 for every community that had confirmed cases in it. The statistical analysis was performed by Stata software and reflects the differences and morbidity prediction for this time interval.We start the analysis by comparing the distribution of morbidity rates in each scrutinized period in Israel by community population density Fig. . Each fiAs shown, in both time intervals, morbidity rates were significantly and positively correlated with population density, though the correlation somewhat weakened in EWII (0.48 vs. 0.23 respectively). This decrease represents the spread of morbidity in EWII also to low density communities, as shown in the figure above. Notably, the low density outliers are invariably either Arab or UO communities.Moving on to the correlation with SES Fig. , we notep < 0.05(. The communities with the highest rates of morbidity (40–60 confirmed cases per 1000), were all clustered at the four lowest SES levels (1–4). Five were OU communities and four were Arab communities, which ranked slightly higher than the OU ones.The correlation thus shifted from negative but insignificant in WI (r = − 0.10) to negative and significant in EWII , were among the most infected in EWII as well. An additional contribution to the significant negative association is the rise in morbidity in Arab communities . Though Arab communities are not as young as OU communities – median ages are 22 and 16 respectively – both these types of communities are younger than the general country population, whose median age is 35 [In WI, the crude data revealed no significant correlation between a community’s percentage of elderly population and its morbidity rates. In EWII, a significant negative correlation was observed, as indicated by the increase of the respective r-values from − 0.07 to − 0.44. These data represent the soaring number of confirmed cases in OU communities, where the percentage of elderly people is extremely low: with a fertility rate of 6.6 children per woman , 58% of N = 69 communities) confirmed cases on average per 1000 population vs. 13.05 (N = 119) . These figures reaffirm the previously noted extensive contagion in Israel’s Arab communities in EWII.The correlation of morbidity with minority status has also changed radically. In WI, as noted above, the morbidity in the Arab sector was significantly lower than in Jewish communities . In EWIIN = 111), in UO communities (N = 8), the respective figure was 40.19. . Though the number of OU communities is small, the large number of confirmed cases indicates that these communities were significantly more affected than non-UO ones.Given the prominence of UO communities among the worst affected settlements, we conducted a separate comparison, distinguishing UO communities from other Jewish Israeli communities. The difference emerged as formidable. Whereas non-OU Jewish communities had 11.10 confirmed Covid-19 cases per 1000 population on average .The percentage of elderly population remained significantly and negatively associated with morbidity rate, but intensified in EWII.Minority status  was significantly and negatively associated with morbidity in WI, with Arab communities sustaining lower probability to morbidity. In EWII, Arab minority status lost its statistical significance, as morbidity in Arab communities rose substantially.The model explains roughly similar portions of the variance in morbidity rate in Israel at the community level: 38% in WI vs. 33% in EWII.The regression highlights several differences:The regression lines presented in Fig. Because the difference in morbidity between UO and non-UO communities emerged as so great in the descriptive statistics, we carried out a Jewish-only regression, distinguishing UO from non-UO Jewish communities Table . As show2, which explained, after the addition, 62% of the variance in morbidity in the Jewish sector in EWII, as compared to 37% in WI . Figure In the regression, too, OU communities differed significantly from non-UO ones, with 17.4* (3.1) additional confirmed cases per 1000, other variables being equal. Once again, then, morbidity rates in OU communities emerge as much higher than in all others and as the most powerful variable in explaining Covid-19 morbidity in Israel (β = 0.43). The addition of UO religiosity is also significant in terms of RUpon concluding, we explored the marginal effect of the socio-demographic variables in interaction with UO religiosity in Jewish communities in Israel.Figure The significant positive association of morbidity with communities’ population density persisted.The negative association of morbidity with community’s SES intensified and became significant in the general country model. The significant negative association of morbidity with the percentage of a community’s elderly population has been maintained and intensified.The negative significant association of morbidity with Arab minority status, which was observed in WI, disappeared in EWII, when the morbidity rates in Arab communities have risen and even surpassed those of Jewish communities, though not to a significant extent.Great gap was observed among UO and other Jewish communities, with the former suffering significantly elevated morbidity rates.To sum up, the regression models revealed the following changes between WI and EWII:,Various reasons can be suggested as underlying the steep rise in morbidity in Israel in EWII. The natural course of the disease; fast release of WI lockdown; lack of government response to the subsequent rise in morbidity; unclear government instructions after WI lockdown; breaches of the regulations by senior public figures, including the state’s President, Prime Minister, Ministers and senior military officers; breaches of the regulations by ‘rank and file’ Israelis due to economic, social and religious pressures; lack of state assistance to people in various forms of need; large public gatherings, mostly for religious rituals, especially during the holidays, attended by both Jewish and Muslim Israelis; ongoing government overlooking of these various breaches.6These figures gain additional weight when compared with those of other countries. To this end, we explored the situation in the period of February to September 2020 in several pandemic stricken European countries of relatively similar population scale: Norway, Austria, Sweden and Ireland. Compared to these countries, in Israel, the gap between the severity of WI and that of EWII was wider than in any of the observed countries , as was the rise in the proportion of death rates . Given Israel’s exceptionally young population, its island-like situation , its hot summer months that might have slowed down the virus spread, the deterioration is especially alarming, raising questions regarding the factors that might have underlain it.Several structural factors seem to have obviously facilitated the disease spread. Israel’s population density is extremely high, exceeding those of all OECD country, but the Netherlands and South Korea.12What was the government’s response to these dynamics? As mentioned, the government’s strategy has changed dramatically over the scrutinized period. Starting out from tight lockdown, early on in WI, it moved on to withdrawal of social restrictions and reluctant enforcement in EWII. According to the Oxford Government Response Stringency Index (GRSI), based on 18 indicators,14Notably, between June 29 and August 17, when the number of daily confirmed cases climbed from 800 to 2071, Israel’s government kept lowering the stringency of its response from 75 to 34. In the subsequent month, from August 16 to September 17, Israel’s government retained its response at a stringency level of 34, lower than that of Sweden, while the number of newly diagnosed cases trebled from a 7-day average of 1383 to 4247 and the number of severely ill Israelis climbed by roughly 50%, from 382 to 573.Under these epidemiological and political circumstances, how did the pandemic spread impact various local subpopulations? As revealed by the preceding analysis, dense, poor, young communities were especially infected. Prominent in this category were UO communities, followed by Arab ones. In UO communities, both the density and poverty have been largely shaped by the communities’ own preference of exceptional fertility rates and low male participation in the labor market, due to prioritization of Judaic studies over gainful employment. In the Arab sector, the crowdedness and poverty were primarily imposed from the outside by decades of discriminatory state policies that marginalized Arab Israelis in education and the labor market. During the pandemic, Arab communities, that were less intensively supported by state allowances and foreign charities (compared to UO communities), were economically injured more pervasively by the lockdowns .Throughout the pandemic, these two sectors were repeatedly condemned for conducting large scale social and religious gatherings. Several points need to be noted in this context. First, Covid campaigns in ArabMore generally, both the UO and the Arab sectors have been socially and politically marginalized in Israel’s public arena for years. The communities’ members live in their own segregated towns, mostly working in sectorial work places and marrying internally. Even linguistically, in the Arab sector and in substantial portions of the UO sector, the spoken languages – Arabic and Yiddish, respectively – are not the country’s official language (which is Hebrew). Politically, too, despite their dramatically different positions in the state’s power structure, both these sectors have been alienated from Israel’s hegemonic Zionist ethos, from the country’s symbolic center and its national narrative and are have been represented by their own sectoral parties since the founding of the State of Israel. Materially, this alienation manifests also in exclusion from the state’s security bodies. Whereas one can dispute the merits of serving in these bodies, participation in any of them is a source of ample material and social benefits, of which both these sectors are excluded. This separateness has probably contributed to the communities’ approach that underlay pervasive non-adherence to government guidelines during EWII.What were the internal circumstances of the pandemic in these sectors? In UO communities, numerous families regularly depend on various types of allowances, most of which have remained intact. These allowances, alongside the highly organized community charities that operate regularly in the UO sector, have protected many UO families. However, the closure of the educational system has brought home many teenage children, who normally attend boarding schools, and rendered the small apartments even denser than they routinely are. The congestion of large families in small spaces increased the risk of contagion. In some cases, it also flared up domestic violence. Though family problems are extremely under-reported in UO communities, preliminary accounts estimated that UO domestic violence calls have quadrupled during the pandemic.In the Arab sector, families and communities sustained over 30% of unemployment and unpaid leave from the early days of the Covid-19 outbreak in Israel. Following this financial decline, 42% of Arab families sunk below the poverty line. Loan applications were, however, mostly declined by banks and other official lenders, thereby forcing people in need to withdraw money from pension savings or else issue grey market loans. Soon thereafter, people who were unable to repay their loans and the high interests they incurred, faced lenders’ violent reactions, which were part of a broader, steep rise in rates of local violent crime. In line with this state of affairs, 30% of Israel’s Arab citizens – twice the percent of Jewish Israelis – have reported, during the pandemic, feelings of insecurity, stress, anxiety and depression and described their psychological state as negative.19Problems and strain of various types abounded, however, also beyond these two sectors. The novelty and volunteering that dominated WI gave way to growing routinization, spreading social, psychological and economic distress, especially in disempowered settings. Economic difficulties and concerns also deepened. In order to assess the scope of the impact, we need to look at the Israeli landscape before the pandemic outbreak.Israel’s cost of living has been extremely high for years, ranked seventh in the world.During the pandemic first months, state support to businesses was minimal and applied only to particular categories.26Social crises also proliferated. Women, in general, have been overrepresented among the pandemic various victims. In September 2020, women comprised 62.7% of unemployed Israelis or those on unpaid leave, roughly twice as men.32Adolescents and young people have also been vulnerable to the tide of morbidity. The number of calls to a domestic violence hotline for youths aged 18–20 increased by 500% vs. 2019.36As elsewhere, elderly people were especially hit by the pandemic also in Israel. As of October, the average age of the dead was 79.5 and the median age was 82. Female victims were slightly older (81.9) than the male (77.6).People who were subjected to social exclusion before the pandemic were particularly harmed by its spread. Prisoners had their home and prison visits cancelled and suffered restricted access to healthcare. Given that roughly 40% of prisoners are diagnosed with chronic illnesses and 73% have had previous psychiatric referrals, and given the growing portion of elderly prisoners, the health implications of the limitations on care services were especially grave in this population.42A pandemic is, evidently, a major social, economic and political crisis. As such, it is reflective and formative of its social context. In Israel, years of underfunding of the health and education systems, growing social fragmentation and economic polarization have preceded the pandemic. Already before the pandemic, 18% of Israeli families and 30% of Israeli children lived beneath the poverty line. Among Arab Israelis, 45% of families were below the poverty line. Poverty among women is 21% higher than among men. Gini coefficient index is roughly 10% higher in Israel than in developed countries.Evidently, the prolonged duration of the pandemic has in itself had its impact. Some of the difficulties depicted above piled up in many communities, well beyond Israel. And yet, the striking differences between the government’s policy in the pandemic’s first wave and the early second wave suggest that grater government involvement and support, as well as stricter enforcement might better protect vulnerable populations, including minority, poor and elderly women and men. The very emergence of the second wave and its exceptional enormity, may possibly be related to the belated, undecided government response to the soaring morbidity that placed Israel far below other island countries that managed to contain the pandemic.Israelis were this badly hit by the covid-19 pandemic. At the time of this writing, nearly 5500 Israelis have died of the disease, representing 600 deaths per million. People suffering all forms of disadvantage have been especially implicated, paying the price of what appeared to be a politicized, reluctant government policy that let the pandemic take its natural, lethal course.The study’s periodization, namely the definition of each of the scrutinized periods, has some limitations. The first time interval, February – June 2, 2020, which was analyzed in the previous article , includeAnother limitation refers to the analysis of Israel’s mixed cities . These communities were classified according to the local majority, i.e., a city with 80% Jewish population was classified as Jewish. In addition to the smoothing of the statistical analysis, this decision was also guided by the (ungrounded) hypothesis that the minority population that lives in a mixed city might possibly adopt some distinct practices that are context dependent. If this is indeed the case, which we cannot substantiate in the present study, then these particular Arab communities may comprise a somewhat distinct subpopulation. We therefore decided to sustain a majority-led classification. One exception to this rule is the city of Jerusalem, where the Arab residents are Palestinians from the occupied West Bank and comprise over a third of the city’s inhabitants. Due to these distinct characteristics, and because it is Israel’s largest city, therefore applying to a larger subpopulation, we divided Jerusalem’s residents according to their Jewish/Arab identities.The second wave of Covid-19 in Israel has profoundly affected marginalized communities characterized by high residential density, low SES and minority status. Other marginalized and disempowered communities have also been badly hit. While acknowledging the potential contribution of various possible causes, we highlight the policy response of Israel’s government during the early weeks of the second Covid-19 outbreak, suggesting that the severe second wave might possibly be associated with belated, undecided government response during this period.