These values are remarkably highfor randomly oriented CNT networks, roughly seven times that of single-walledCNT films. The enhanced thermal conduction is due to the additionalwall, which likely gives rise to additional heat-carrying phonon modesand provides a certain resilience to defects. Our results demonstratethat free-standing double-walled CNT films efficiently dissipate heat,enhancing our understanding of these promising films and how theyare suited to applications in EUV lithography.Nanomaterials are driving advances in technology dueto their oftentimessuperior properties over bulk materials. In particular, their thermalproperties become increasingly important as efficient heat dissipationis required to realize high-performance electronic devices, reduceenergy consumption, and prevent thermal damage. One application wherenanomaterials can play a crucial role is extreme ultraviolet (EUV)lithography, where pellicles that protect the photomask from particlecontamination have to be transparent to EUV light, mechanically strong,and thermally conductive in order to withstand the heat associatedwith high-power EUV radiation. Free-standing carbon nanotube (CNT)films have emerged as candidates due to their high EUV transparencyand ability to withstand heat. However, the thermal transport propertiesof these films are not well understood beyond bulk emissivity measurements.Here, we measure the thermal conductivity of free-standing CNT filmsusing all-optical Raman thermometry at temperatures between 300 and700 K. We find thermal conductivities up to 50 W m An integral part of this trendis the miniaturization of components as well as the incorporationof new functionalities such as mechanical flexibility. In this regard,nanomaterials offer distinct advantages over traditional materials,such as bulk silicon, due to their reduced dimensionality. One typeof nanomaterial that has received significant interest is networksof one-dimensional materials, such as nanowires or nanotubes madefrom materials such as silicon, SiC, and bismuth.5 Heat dissipationis a critical issue for both flexible and nonflexible electronics.In the former, typical polymer substrates such as poly,PET, have comparatively low thermal conductivities <0.2 W m–1 K–1.6 For applications such as interconnects in microelectronics, CNTfilms are already important due to their favorable thermal properties.7 For another application, namely, EUV pellicles,the CNT thermal properties and ability to withstand the heat associatedwith EUV exposures become vital, next to high EUV transparency andmechanical strength of the CNT membrane.8Carbon nanotubes (CNTs) are a nanomaterialwith excellent electricaland mechanical properties that make them a promising material forflexible electronics, with device applications in chemical and biologicalsensing, transparent electrodes, and displays, some of which are alreadyavailable in the market.10 Crucial to this advancement is the development of pellicles thatprotect the photomasks from damage during lithography. EUV pellicleswere initially fabricated with polysilicon (pSi), but their low EUVtransmission (83%) motivated the search for other material systems.11 In addition, the thermal conductivity (κ)of pSi films is rather low, with κ = 14 W m–1 K–1 for a 1 μm thick film.12 For thinner films, the increased boundary scattering furtherreduces this value. This is true for both pSi and single-crystal silicon,where the thermal conductivity drops 15-fold as the thickness decreasesfrom 1 μm to 9 nm.13 Other materialsinclude thin graphite or silicon nitride films. Thin graphite filmsgrown by chemical vapor deposition have a higher thermal conductivity(κ ≈ 700 W m–1 K–1)14 but a smaller EUV transmission (70%),15 which limits their applicability for EUV lithography.Amorphous silicon nitride has a lower thermal conductivity (2.7 Wm–1 K–1)16 and a relatively high EUV absorption (14% for a 16 nm membrane),which leads to overheating and failure of these films under EUV powers>80 W.17 To be thermally stable, a pellicleshould have a high EUV transmission and a high thermal conductivityas this will lead to the smallest temperature increase due to EUVabsorption. Different materials can handle different heat loads, butas a starting point, the EUV transmission should be >90%18 and the thermal conductivity should ideallybe higher than that of current materials that are considered for EUVpellicles, which means above 10 W m−1 K−1. None of the above candidates satisfy these requirements. However,several novel pellicle materials have been proposed to support futureEUV scanners with higher source powers and associated technology nodes,in particular, metal silicide composite material and CNT-based pellicles.19Advances in EUV lithography are driving the miniaturizationofintegrated circuits to the 5 nm process level and beyond.20 Recent demonstrationshave shown that CNT pellicles have minimal impact on wafer imagingduring exposure in an EUV scanner.21 Thestability of free-standing CNT films under high EUV powers motivatesthe study of their thermal properties. Individual CNTs are among thebest conductors of heat with room-temperature thermal conductivitiesgreater than 2000 W m–1 K–1.23 This is reduced by one or more orders of magnitude in films andsheets made from CNTs as the tubes form a percolation network (κ= 0.5–200 W m–1 K–1).30 Notably, there is an absence of experimental studies on the thermalproperties of double-walled CNT networks.31 We also note that in most studies, the CNT films are supported ona substrate. Disentangling the intrinsic and extrinsic factors contributingto thermal transport is not trivial. Therefore, determining the intrinsicthermal conductivity of free-standing CNT films, in particular, double-wallednetworks, is both technologically relevant and fundamentally interesting.Free-standing CNT films consisting ofa randomly oriented CNT networkhave been found to be a promising pellicle material candidate forhigh EUV source powers, exhibiting high EUV transmission and thermaland mechanical stability as well as offering a range of additionaladvantageous material properties.32 Usingthe temperature-dependent frequency of the G+ Raman mode,we determine the thermal conductivity at temperatures between 300and 700 K of single-walled and double-walled CNT films . The reported values are smaller than those forindividual nanotubes, highlighting the role played by intertube junctionsin thermal transport of CNT networks.39 Interestingly, DWCNT films are roughly seven times as thermallyconductive as SWCNT films with comparable EUV transmission. This suggeststhat the second wall prevents additional phonon-defect scattering,which would otherwise impede thermal transport, and provides a parallelchannel for heat conduction. Importantly, these films efficientlydissipate heat, making them suitable for applications such as EUVpellicles, interconnects in integrated circuits, and components inflexible electronics.In this paper, we investigate the thermal conductivities of free-standingCNT films using Raman thermometry.40 SWCNTs were collected directly after their synthesis in a floatingcatalyst chemical vapor deposition reactor onto a microporous filter.Random CNT films were further transferred to a support frame and densifiedwith a solvent.66 DWCNT films were firstassembled onto a filter from a CNT dispersion by means of vacuum filtration.After filter removal, the DWCNT film floating in solution was transferredonto a support frame to form the pellicle membrane.40We investigated two types of free-standingCNT films containingeither SWCNTs or DWCNTs, which were fabricated as follows.Table S1 summarizes the thicknessand optical properties of these films. We used atomic force microscopyto determine the film thickness, see Note S3. The two SWCNT films have thicknesses of 10.9 nm (S1) and 26.6 nm(S2), controlled by varying the CNT collection time. For the thickerfilm, the visible transmission at 550 nm is lower (89.7% comparedwith 93.2%). Notably, although the DWCNT film is the thinnest (8.6nm), it has the lowest transmission (88.6%). This is due to the additionalwall in the nanotube structure, which increases absorption.We study three samples: one DWCNT film (D1) andtwo SWCNT films(S1 and S2). 43 The first variation of the technique, one laser Ramanthermometry (1LRT), uses a continuous-wave laser beam both as a thermometer and heatsource, see To study the thermal properties of free-standing CNT films, weuse two variations of Raman thermometry. This noninvasive, all-opticaltechnique, also referred to as optothermal Raman spectroscopy, iswidely used to measure the thermal conductivity of nanomaterials.The noninvasive aspectof the Raman thermometry technique is particularlyadvantageous to study free-standing thin films, as no additional fabricationsteps are necessary, thereby allowing a direct and reliable determinationof the intrinsic thermal properties of materials such as CNT pellicles.42t is the film thickness, r0 is the laser spot size, and α is a geometricterm (≈1). χT and χP arethe changes in Raman mode frequency as a function of temperature (χT) and absorbed laser power (χP), respectively. R is the thermal decay length, which is the length overwhich the system returns to ambient temperature. Details on how weobtained the absorbed laser power are given in Note S4.To estimate the thermal conductivity, we consider that the heatflux is directed radially outward from the laser spot. In other words,the heat carried by phonons diffuses from this hot spot. This is validassuming that the material has uniform absorption in the out-of-planedirection and isotropic in-plane thermal conductivity. We neglectradiative cooling based on calculations in ref  for simi2LRT)—the additionof a second focused laser allows for the decoupling of the heat sourceand temperature probe, 32 In this configuration, theprobe laser maps the temperature profile by obtaining spatially dependentRaman spectra with respect to a fixed pump laser that locally heatsthe sample. In this way, this technique directly maps the thermalfield distribution. We obtain the thermal conductivity using the followingexpression, which is valid in a regime where the thermal field decayslinearly in ln r(P is the absorbed laserpower and t is the sample thickness. κ is obtainedfrom the slope of the temperature (T) against ln(r). In contrast to 1LRT  focused via ahigh NA objective to a 1/e spot size of r1/e = 0.88 μm. In 1LRT, the Raman laser spot acts both as a heater and asa local temperature probe; see 2LRT, the heat source was a 405 nm laser placed below thesample (r1/e = 0.79 μm), see P <5 × 10–3 mbar housed the samples. The vacuumconditions both protected the samples from atmospheric contaminationand eliminated unwanted heat dissipation processes due to convectionand thermal conduction to the air. We used vacuum conditions for bothtypes of Raman thermometry measurements.In order to useRaman thermometry techniques, we first identifya temperature-dependent Raman mode in the samples, which we use fortemperature calibration. The Raman spectra were collected using aHoriba T64000 Raman spectrometer in a single-grating configurationwith a 2400 g/L grating. All Raman measurements were carried out usinga diode laser  and the other around 1570 cm–1 (G–), that arise from the longitudinal (G+) and circumferential (G–) motions of thecarbon atoms in the nanotube, respectively. The G+ modefrequency is particularly sensitive to doping,50 strain,52 and temperature54 while being independent of tube diameter (dt). On the other hand, the G– frequency isdependent on dt.47 Hence, the G+ mode is the most suitable for Raman thermometrymeasurements. In the results that follow, we will use the frequencyof the G+ Raman mode as a local temperature probe. Thehigh-resolution spectrometer used in this work and the high accuracyof the peak fitting algorithms result in a spectral resolution approaching0.05 cm–1. This would allow for the detection ofsmall changes in temperature (∼2 K). Ultimately, we are limitedby the spatial inhomogeneity of the G+ mode , whichcorresponds to a temperature uncertainty of ΔT ∼ 30 K.–1 arisefrom the D and 2D phonon modes  intensity of the 2D (D) mode compared to that ofthe SWCNT film suggests that the DWCNT sample has fewer defects andbetter electronic quality.58 The low-frequencyradial breathing modes (RBMs) found between 100 and 500 cm–1 arise from the coherent, radial, out-of-plane motion of carbon atomsand are unique to CNTs.49 In the insetof Having identified a suitable temperature-dependentRaman mode,we briefly turned our attention to the other features in the Ramanspectra. The peaks around 1340 and 2680 cmodes see 2, which + Raman mode, we nowcalibrated the frequency shift while heating the sample. Using the temperature-dependent G–1. This is due to the softening of the G phononmodes.54 By tracking the G+ peak frequency(ωG+) as a function of stage temperature,we obtain the temperature coefficient χT = dω+G/dT = −0.028 cm–1 K–1, 59 and SWCNT filmssupported on SiO2.60 Here, thelow-power laser acts as a nanoscale temperature probe.Increasing the temperature by 100 K red-shiftsthe G modes by approximately3 cm+ peak frequency representsthe lattice temperature of the free-standing CNT network, we now studythe dependence on absorbed laser power; see + mode frequency because the absorbedoptical energy heats the pellicle, leading to the softening of thephonon modes. +G on theabsorbed laser power. The power coefficient is χP = dω+G/dP = −0.066cm–1 μW–1. This value isgreater than that in previous reports of SWCNT films supported onSiO2 (χP = −0.01 cm–1 μW–1).30 Thereason that we observe a larger shift, and thus a larger temperatureincrease, for the same power is that in their case, heat sinking intothe SiO2/Si substrate was present, meaning that they requireda larger power to reach the same temperature increase, which correspondsto a smaller χP. For free-standing CNT films, thelocal temperature depends exclusively on the ability of the CNT networkto dissipate heat. We obtain the thermal conductivity using the temperatureand power coefficients in R) tobe the distance over which the temperature decays from 80 to 20%,we calculate κ = 49.5 ± 9.1 W m–1 K–1 for the DWCNT sample using R ≈100 μm. We note that if we take the decay length to correspondto the 90 to 10% decay length, we would find R ≈130 μm. This would result in a thermal conductivity of 52 Wm−1 K−1, which is within the reporteduncertainty.Havingverified that the G2LRT), we obtained thespatial temperatureprofile shown in Using two-laser Raman thermometry .This describes the thermal transport close to ambient temperature(300 K). Using –1 K–1, whichis in good agreement with the values obtained from 1LRT. Here, the clearadvantages of the 2LRT technique are that we obtain the thermal conductivity close to roomtemperature and that we make no assumptions on geometry as we directlyvisualize the steady-state temperature profile, which directly relatesto the thermal conductivity.In the effective thermal conductivity of the composite CNT films,κeff. Later, we corrected for the porosity and extracteda skeleton thermal conductivity of the CNT networksthemselves, which we will call κCNT. The effectivethermal conductivity (κeff) for the investigatedCNT samples, which ranges from 6 to 50 W m–1 toK–1, is plotted in Table S1,we report the optical and thermal properties of each sample. The effectivethermal conductivities of these CNT networks are 2 orders of magnitudelower than those for isolated CNTs due to the presence of voids andintertube junctions that restrict the thermal transport in the CNTnetwork by introducing boundary resistance.39 These junctionsalso act as filters of phonons with mean free paths greater than thedistance between the junctions, greatly reducing the cumulative contributionto κ.39Having established that both techniquesproduce similar valuesof thermal conductivity, we now investigated the different samples.First, we note that the thermal conductivity that we obtain is an eff = 6.9 ±2.4 W m–1 K–1 from 1LRT and κeff = 7.8 ± 0.8 W m–1 K–1 from 2LRT.These values arecomparable to those of SWCNT S2, with κeff = 7.4± 1.1 W m–1 K–1 from 1LRT and κeff = 5.7 ± 0.9 W m–1 K–1 from 2LRT.This is expected as both are SWCNT samples, and the 1LRT and 2LRT fit to the dataaccounts for differences in thickness and in visible transmission.For SWCNT S1, κeff = 49.5 ± 9.1 W m–1 K–1 from 1LRT and κeff = 44.0 ± 9.9 W m–1 K–1 from 2LRT.This is roughly seven times higher than that of SWCNT S1 of similarthickness and EUV transmission, which suggests that the differencein visible transmission alone, which differs only by a few percent(see Note S4), cannot explain the enhancedthermal transport. Indeed, DWCNTs have an additional wall that providesboth a parallel conduction channel for thermal transport and robustprotection against defects that occur in a single wall. In additionto the intertube junctions, phonon-defect scattering also filtersout medium and long mean free path phonons further reducing the effectivethermal conductivity.61 The lower relativeintensity of the D peak in Interestingly, the DWCNT D1 film has the largest effective thermalconductivity with κT/∂ ln (r) close to 300 K, we bin the datainto distinct temperature regimes, Having identified the different valuesof effective thermal conductivityin the samples, we now investigated the temperature dependence oftheir thermal properties. Typically, the effective thermal conductivitychanges with temperature. The reduced phonon population at low temperaturesand increased phonon–phonon scattering at high temperaturessuppress thermal transport. Here, we evaluate the effective thermalconductivity as a function of temperature above ambient conditions.Rather than only extracting the slope of ∂eff(T), for the DWCNT films D1 and SWCNT S2films. In both cases, κeff(T) islargest close to 300 K before reducing at higher temperatures. Thedashed lines show a temperature dependence of the form κeff(T) ∝ T–2, which has previously been reported for individual SWCNTs23 and is ascribed to second-order three-phononscattering processes involving two acoustic phonons and one opticalphonon, as shown schematically in the inset. Previous studies reportedthat the junction thermal conductance is independent of temperature.39 This result implies that while the intertubejunctions limit the overall thermal resistance, the temperature dependencearises from the remaining conduction channels and therefore reflectsthe intrinsic properties of the CNTs themselves. Moreover, our observationof a relatively strong temperature dependence and relatively higheffective thermal conductivity of the CNT network suggests that defectsdo not play a significant role. This is consistent with our Ramanspectra, which show very small D peaks ,63 reflecting the random orientationof individual CNTs within these networks. Indeed, the alignment ofSWCNTs by filtration and a high magnetic field increases the thermalconductivity substantially (κeff = 210 W m–1 K–1).24 We note thatin most studies, the CNT films are supported on a substrate. Disentanglingthe intrinsic and extrinsic factors contributing to thermal transportis not trivial. Therefore, by using free-standing CNT films in thisstudy, we directly probe their intrinsic thermal properties.We will first discuss the effectiveconductivity of the entireCNT film including voids κ–1 K–1, for compressed randomnetworks with a volume fraction of 0.19,38 to κ = 50 W m–1 K–1 measuredin the direction parallel to aligned MWCNTs.25 For the former, weak bonding between nanotubes impedes thermal transportacross nanotube junctions. Interestingly, our results on DWCNT D1reveal a higher thermal conductivity (κeff ≈50 W m–1 K–1) than that in typicalrandomly oriented films of single- or multi-walled CNTs (κeff ≈ 0.2–2 W m–1 K–1).63 Hence, aligning DWCNTs within the network shouldoffer further improvements in the thermal conductivity.Literature reports of the effective thermal conductivity for multiwallcarbon nanotube (MWCNT) films typically range from κ = 0.2 Wm1LRT and 2LRT arethe effective thermal conductivities of composite films formed byCNTs and voids. In order to obtain the conductivity of the CNT networkitself, we follow ref (Note S2), we obtain porosities ϕof 0.301 and 0.254 for the DWCNT and SWCNT, respectively. We thenuse the Maxwell-Garnett effective medium model to obtain the volumecorrection factor CNT using κeff = < cos θ > κCNTVCNT, where < cos θ> = 1/3 represents the angulardistribution between the CNT axis and direction of heat flow in arandomly oriented film. We determine the CNT skeleton conductivityto be κCNT = 257 W m–1 K–1 and κCNT = 35 W m–1 K–1 for the DWCNT (D1) and both SWCNT samples (S1/S2), respectively(see Note S2). These values are relevantfor comparison with composite materials containing CNTs.65It isimportant to note that the thermal conductivities that wehave obtained using llow ref  and firs+) with temperature, we map the thermal field and extract thetemperature-dependent thermal conductivity, κ(T). At 300 K, κ was measured to be 49.5 W m–1 K–1 for the DWCNT films and 6.9–7.4 W m–1 K–1 for the SWCNT films. The significantlyhigher value for DWCNT films arises from the reduced phonon-defectscattering and additional conductance channel due to the presenceof the second wall in the structure of the nanotube. In addition,aligning the CNTs should further increase this value. At higher temperatures,the thermal conductivity decreases from the value at 300 K followingthe power law: κ(T) ∝ T–2. This dependence is due to second-order three-phononscattering processes. Interestingly, although the presence of junctionsbetween neighboring nanotubes impedes the overall thermal conductivity,the underlying thermal transport mechanism has the same dependenceas that for individual nanotubes. In future work, it will be interestingto study in more detail how the effective thermal conductivity ofthe CNT network is related to the microscopic structure of the network,for example, considering the number of tube–tube interconnections.In conclusion, we experimentally studiedthermal transport in free-standingCNT films using Raman thermometry at temperatures between 300 and700 K. By calibrating the softening of a suitable Raman mode (G–1 K–1) and of the CNT network alone(257 W m–1 K–1) allows for efficientthermal management in flexible devices. The electrical and thermalproperties of CNT films are also relevant for applications such asinterconnects in integrated circuits, where traditional materialssuch as copper perform significantly worse at reduced dimensionality.The efficient heat dissipation of free-standing CNT films is attractivefor EUV pellicle applications, where a highly EUV-transparent pelliclematerial must withstand the heat associated with EUV exposures. Thisstudy of the thermal properties of both SWCNT and DWCNT free-standingfilms enhances our understanding of how CNTs can advance various applications.For example, the relatively high effective thermal conductivity ofthe DWCNT film containing the CNT network and voids (49.5 W m


Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scalers poses a significant health risk to oral health practitioners from airborne pathogens. Aerosol generation varies with different HSH designs, but to date, no study has measured this.We measured and compared aerosol generation by (1) dental HSHs with 3 different coolant port designs and (2) ultrasonic scalers with no suction, low-volume evacuation (LVE) or high-volume evacuation (HVE). Measurements used a particle counter placed near the operator’s face in a single-chair, mechanically ventilated dental surgery. Volume concentrations of aerosol, totaled across a 0.3–25-µm size range, were compared for each test condition.P < .001) with total volume concentrations 4.73×108µm3/m3 and 4.18×107µm3/m3, respectively. For scaling, mean volume of aerosol was highest with no suction followed by LVE and HVE (P < .001). We detected a negative correlation with both LVE and HVE, indicating that scaling with suction improved operator safety. For drilling, simulated cavity preparation with a 1-port HSH generated the most aerosol (P < .01), followed by a 4-port HSH. Independent of the number of cooling ports, lack of suction caused higher aerosol volume (1.98×107 µm3/m3) whereas HVE significantly reduced volume to −4.47×105 µm3/m3.HSH drilling and scaling produced significantly high aerosol levels (High concentrations of dental aerosol found during HSH cavity preparation or ultrasonic scaling present a risk of infection, confirming the advice to use respiratory PPE. HVE and LVE both effectively reduced aerosol generation during scaling, whereas the new aerosol-reducing ‘no air’ function was highly effective and can be recommended for HSH drilling. Most modern HSHs incorporate air or air–water coolant ports, designed to spray water to improve cutting and polishing efficiency while minimizing pulp injury. The water coolant and the rotary cutting bur generate aerosol which, when combined with oral fluids creates bioaerosol. (Bio)aerosols may remain in the air for protracted periods, and they have the potential to transmit respiratory infections to oral health practitioners.In dentistry, the high-speed handpiece (HSH) is used for removing tooth structure to prepare teeth for restoration. Oral health practitioners face the greatest risk of contracting COVID-19 from aerosol exposure, more so than nurses and general physicians, and the WHO recommends that oral health clinicians employ strict personal protection measures to avoid or minimize aerosol-producing procedures. Guidelines on the provision of dental services during the COVID-19 pandemic have been frequently updated. Policy documents focus on dental instruments as aerosol sources and recommend rubber-dam and high-volume evacuation (HVE) suction as mitigating measures. Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) is the primary current concern, but our findings apply to many airborne pathogens.The ongoing coronavirus disease 2019 (COVID-19) pandemic has recorded >476 million cases and >6.1 million deaths so far. For example, air-turbine HSHs allow rapid preparation of dental hard tissues with minimal pulpal damage, but they create considerable aerosol. Conversely, electric-motor HSHs offer constant power and rarely stall, potentially creating less bioaerosol. Some dental HSHs include a function that directs air onto the cutting surface to help cool the tooth, disperse water spray, and clear debris. This ‘chip air’ function produces higher aerosol levels but can be deactivated in newer handpieces. Currently, few reports have quantified how much aerosol is produced by different types of HSHs, including those with or without the ‘chip air’ function. Furthermore, the literature shows that ultrasonic scalers produce ∼3 times the bioaerosol compared to hand instruments.Depending on the design, HSHs generate different levels of aerosol. Evaluating the effectiveness of different types of suction systems for drilling and scaling is important in developing standard guidelines for oral health practitioners to minimize cross infection by airborne pathogens.To reduce aerosol production and to provide a drier operation field during dental procedures, low-volume evacuation (LVE) or high-volume evacuation (HVE) suction systems may be employed.In this study, we compared aerosol generation (1) in dental HSHs with 3 different coolant port designs , with and without the new aerosol-reducing function  and (2) in ultrasonic scalers operated under 3 different suction conditions . We formulated 2 null hypotheses: (1) There is no significant difference in aerosol levels generated between dental HSH with the 3 different coolant-port designs and (2) there is no significant differences in aerosol levels generated during ultrasonic scaling with the 3 different suction conditions.3/s or 4.1 air changes per hour [ACH]). Air entered the room through a ceiling grille above the foot of the dental chair and passively exhausted through a ceiling grille above the head of the dental chair. To reduce background particle concentration, all surfaces  were cleaned, and operators wore clean personal protective equipment (PPE). A Sheffield HEPA-13 air purifier  was run at maximum fan speed, with a clean air delivery rate of 320 m3 per hour . The purifier was run for 40 minutes before the sequence of measurements commenced, and it ran continuously throughout the measurements at maximum fan speed. The air filtration rate, being twice the ventilation rate, had a significant effect on the background particle concentrations but was not expected to significantly affect the concentration at the operators’ location. The concentration of particles here is dominated by the production of aerosol at the patient’s mouth, and the particles are measured within seconds of their generation.Tests were conducted using a dental mannequin in an enclosed, windowless dental surgery. The floor space measured ∼3.9 m × 3.5 m × 2.7 m. The room was mechanically ventilated : (1) an AeroTrak 9306  mounted on a tripod at roughly the position of the dental practitioner’s face and (2) an AeroTrak 9310 (with isokinetic inlet 700068) placed on a bench located along the wall opposite the dental chair. Both counters independently measured particle concentrations in 6 size ranges: 0.3–0.5 µm, 0.5–1.0 µm, 1.0–3.0 µm, 3.0–5.0 µm, 5.0–10.0 µm, and 10.0–25.0 µm. A Kestrel 5000 Environmental Meter  logged temperature and humidity at 1-minute intervals. The Dental Council of New Zealand does not normally specify ventilation rates for dental surgeries, but it did release some guidance during COVID-19 alert level 2 in 2021.  This guidance stated that rooms with 1–2 ACH were to be considered poorly ventilated and that high-volume suction was to be considered essential in such rooms. It specified stand-down periods after aerosol-generating procedures of 10–30 minutes depending on what combinations of evacuation and dental dams were used. The net ventilation rate of 8.6 ACH in our test room is high for most mechanically ventilated buildings, but it falls within ASHRAE recommendations of ≥6 ACH for most treatment rooms other than operating theatres. We considered that, given that the building ventilation supply is filtered, 8.6 ACH provided an acceptably low level of background particle concentration for these tests.Various oral health activities simulated by an operator and assistant were classified into 17 types: ‘consultation: talking, no purifier’; ‘consultation: silence, no purifier’; ‘triplex, no purifier’; ‘movement of people (pax) (simulating a patient/person), no purifier’; ‘lunch, no purifier’; ‘preparation, no purifier’; ‘consultation: talking’; ‘consultation: silence’; ‘triplex’; ‘movement of pax’; ‘purifier ON’; ‘scaling’; ‘rest ’; ‘preparation’; ‘drilling’; ‘test of handpiece setting’; and ‘room empty.’ Suction was classified into HVE suction, LVE suction, or no suction. For drilling, 4 location classifications were used: upper incisor, upper left molar, lower front incisor, patient’s right, or lower right molar. Also, 3 drilling directions were used: rear, front, or occlusal. Finally, 3 handpiece configurations were used: ‘1 port, water and spray, NSK Z85 at maximum air pressure,’ ‘4 ports, water and spray, NSK Z95L at maximum air pressure,’ or ‘4 ports, water, NSK Z95L at maximum air pressure and no spray.’The AeroTrak instruments accumulated particle counts in 6 size ranges (channels 1–6): 0.3–0.5 µm, 0.5–1.0 µm, 1.0–3.0 µm, 3.0–5.0 µm, 5.0–10 µm, and 10–25 µm. Assuming that all measured particles were spherical with a uniform size distribution, the volume mean diameters for each channel were 0.42 µm, 0.83 µm, 2.4 µm, 4.2 µm, 8.3 µm, and 20 µm, respectively. The particle concentration (number per unit volume) in each channel was multiplied by the volume mean diameter for that channel to calculate the particle volume per unit volume of air sampled. These data were summed over all 6 channels to calculate total particle volume per unit volume of air sampled.In our experiment, a persistent background level of particles was not generated by dental treatment activity . During the ‘rest’ activities, the concentrations measured by the Aerotrak 9310 instrument (at a distance from the practitioner) corresponded well with the Aerotrak 9306 instrument (near the practitioner). Therefore, the Aerotrak 9310 measurements were assumed to be equal to the background aerosol concentration. Minute differences between the 2 instruments during these rest periods were attributed to the noise inherent in particle counting and the spatial nonhomogeneity of the air currents. The AeroTrak 9310 data were subtracted from the AeroTrak 9306 data to obtain the excess aerosol concentrations released in the vicinity of the dental practitioner by the activities of interest. The mean over each consecutive 30-second counting interval during each activity of interest was calculated. The mean over the repeated measurements of the same type of activity was then calculated.Two operators (1 clinician and 1 assistant) were present, dressed in minimum PPE requirements  according to the DCNZ COVID-19 level 1 guidelines.The clinician performed the ultrasonic scaling and drilling operative procedures following the same sequence for each test Fig. . All simFor ultrasonic scaling, each test was carried out with a Varios2-LUX scaler (NSK) with a type G6 tip and the recommended G8 (80%) power setting. Scaling started from the distal side of the last molar in quadrant 1 , continuously moving to Q2, Q3, and Q4 for 2 minutes per quadrant  surfaces. The central incisor was chosen to demonstrate maximum aerosol generation because this tooth has the least soft-tissue barrier. A class II cavity preparation  on the first molar was chosen because this tooth has a higher caries incidence among adults.P < .05. The effects of the dental operative procedures and the corresponding variables were also investigated using the Pearson correlation coefficient . Because the signal noise in the measurements is considerable, R values of >0.1 and <−0.1 were interpreted as evidence of correlation.Dental aerosol levels generated during different operative procedures (section 2.4) were compared using the Kruskal-Wallis and post hoc tests. Dental aerosol particle volume levels were compared using the Mann-Whitney U test. Statistical analyses were conducted using SPSS version 27 software  with statistical significance set at 8 µm3/m3 and 4.18(±1.22)×108 µm3/m3, respectively, which were significantly higher (P < .001) than those generated with other activities, for example, by talking during the patient–clinician consultation, using the triplex air-water syringe, or during rest periods ×104µm3/m3), with the least aerosol generated when HVE was used (P < 0.001) (Table P = .01) , followed by drilling with the 4-port handpiece and 4-port handpiece with no air function ×105µm3/m3). The mean level of aerosol produced by drilling (with no suction) was also influenced by the location of cavity preparation   with the 1-port HSH showed the highest aerosol level . In the current study, we have provided a standardized protocol, and our findings can act as a baseline reference for other variables of interest. Because the focus of the current study was to measure and compare the effect of different suctions and air supplies for dental high-speed handpieces and ultrasonic scaling, only 1 brand or type per variable was investigated, which could be a limitation of the study. Further work should include a variety of types (and brands) of handpieces, scalers, and suction systems to investigate their relative ability to reduce aerosol level under identical in vivo clinical conditions. A disadvantage of or approach is that it does not test the effect of other precautions .To investigate the different combination of variables for generating aerosol in dental operative procedures, we preferred the air sampling method over the ‘settle plate’ methodology. Although most dental aerosol studies have utilized the ‘settle plate’ method, Ultrasonic scalers and the efficiencies of different suction types, in particular, have been topical in the current pandemic. Dental hygienists traditionally provide care with the aid of a dental assistant, due to the bulkiness of the high-volume suction (HVE) and difficulties in maneuvering it. Dental hygienists working solo prefer using the LVE  suction system, which is less bulky and easier to use than HVE suction. Moreover, LVE saliva ejectors provide an easy means of clearing the operating field and better patient comfort than HVE suction.Our finding that high-speed handpieces and ultrasonic scaling produce the most concentrated dental aerosol aligns well with the current literature. Other guidelines state that aerosol production by dental handpieces is complex and dependent on multiple factors such as handpiece speed, mix of air and water, coolant ports and types of bur used, which have been investigated in the current study.Many clinical guidelines recommend 4-handed dentistry during the COVID-19 pandemic and that HVE be used during all dental treatment to minimize aerosol production.; however, it disagrees with the findings from Matys and Grzech-Lesinka. Interestingly, there was a statistically significant difference in aerosol particle levels between scaling with HVE and LVE. This contradicts the findings of Holloman et al, who found no difference in aerosol and spatter reduction during ultrasonic scaling with different suction types. This is likely due to a difference in sampling method , the distance between the operative area and sampling units, and the wider scatter that we observed. Moreover, Holloman et al measured real infection risk, whereas our study focused on measuring on aerosol generation alone. Yang et al also mentioned that simulated environments without a live patient is a limitation of many studies. However, regardless of saliva transmission and presence of patients, the efficacy of different suction should not change whether the experiment is done in the human mouth or mannequin because the procedure is the same. In fact, patients create more variables because each patient’s oral hygiene and requirements of restorative work vary. Hence, the value of standardizing the experiment and eliminating potential variables outweighs the limitation of using mannequins. Previous studies that mainly measured aerosol and splatter during ultrasonic scaling with HVE and LVE also reported significant differences between the 2 variables, with reports of a ∼90%–93% aerosol reduction.Our results show that both HVE and LVE significantly reduced the aerosol level for scaling. Whereas HVE was very efficient in reducing aerosol particles all sizes to a minimum level, LVE was more effective in the larger particle range. This finding is consistent with previous studies In the present study, we considered particle volume, summed over the size range measured. Some of these particles will consist solely of irrigation or cooling water and carry no pathogens. Others will carry a proportion of the patient’s saliva and present an infection hazard. The proportion may vary with particle size and where in the oral cavity they originate. Particle size determines where in the infectee’s airway the particles deposit, which can affect infection severity. This is an area that might benefit from future research.In SARS-CoV-2 infections, when aerosol is emitted by a person breathing and/or speaking, particles of <5 µm in diameter carry more virus than larger particles. Although we observed similar trends to those reported by Matys and Grzech-Lesniak, they reported a significantly lower concentration of aerosol particles, which could be explained by differences in room size, the distance at which the particle sensor was placed, and/or different settings on their air-purifier system.The effectiveness of HVE was evident for drilling as well, regardless of the number of coolant ports used and the location of teeth. The most significant finding was that HVE was effective in removing all sizes of aerosol particles measured. This is noteworthy because previous reported methodologies failed to measure small aerosol particles (0.5–10 µm). Small particles deposit in human pulmonary bronchioles and alveoli. Our study demonstrates that using either HVE or LVE significantly reduces aerosols of this particle size during drilling and scaling Fig. b.4,14,3 found that effective ‘no chip air’–mediated reduction of aerosol is possible while maintaining a thermally safe environment for the tooth.One novelty of our study was the evaluation of the ‘no chip air’ aerosol-reducing function found on newer HSHs. Conventionally, aerosol exposure is managed using HVE, by decreasing handpiece speed, or by using handpieces with fewer coolant ports. Although the new ‘no chip air’ function is innovative, whether the absence of air spray could affect the pulpal temperature of the drilled tooth remains unknown. More recently, Lempel and Szalma the time and distance variables of droplets remain unknown. The present study was conducted in an enclosed clinical room and should be repeated in an open clinical environment with single- or multiple-chair units to determine whether the safer combination of suction systems, and handpiece and scaler spray functions still apply.We investigated the effect of suction systems and air spray settings for dental HSHs and ultrasonic scalers on aerosol generation. Following the air sampling protocol described here, future research could involve other aerosol-related variables . Although it has been reported that droplets take 30–0 minutes to settle,In conclusion, within the current study limitations, we report several findings. The most intensive dental aerosol was generated by high-speed handpieces and ultrasonic scaling. Caution should be exercised during these procedures to minimize cross infection. For scaling, the HVE suction system was more effective in reducing aerosol generation than LVE suction or no suction at all. We recommend the new aerosol-reducing ‘no chip air’ function (if available) for cavity preparation as the function is highly effective in reducing the aerosol generated, regardless of the number of coolant ports and the location or type of tooth being prepared.


In this study, an indoor 4 μL·L−1 NO2 simulated fumigation test was conducted with three treatments, CK , T1 (4 μL·L−1 NO2 + 8 h/d), and T2 (4 μL·L−1 NO2 + 24 h/d), which were set up with considerations for time and concentration. The results demonstrated that most of the morphological parameters of B. glabra ‘Elizabeth Angus’, except for the floral organs, were decreased in the root, stem, leaf, and bract. Continuous fumigation significantly attenuated the growth rate and reduced the water and pigment contents of organs. Excessive NO2 reduced the number and transfer rate of photoelectrons by destroying the photosynthetic reaction center, which in turn weakened photosynthesis, but the plants with intermittent fumigation recovered after fumigation. The Kaplan-Meier (K-M) survival curve displayed median survival periods of 41 and 55.5 h for T1 and T2, respectively, and the morphological structure and most of the indicators of photosynthetic reaction centers changed significantly during stress. Acute injury to B. glabra ‘Elizabeth Angus’ was caused by 4 μL·L−1 NO2, and B. glabra ‘Elizabeth Angus’ had limited ability to regulate high concentrations of NO2 acute stress.The air pollutant NO However, the expansion of urban and industrial areas in recent years has resulted in excessive emissions of air pollutants, primarily including sulfur dioxide, nitrogen oxides, and particulate matter, which have had significant adverse impacts on plant life. Among these pollutants, nitrogen dioxide  positively affect plant growth, while medium to high concentrations (1–4 μL·L−1) have a negative effect. In general, changes in plant surface traits are often caused by specific gene expression levels and metabolic activity changes within the plant [2 stress. Apparent traits and anatomical structure are important indicators to measure the degree of damage [2 stress [2 environment, such as root atrophy [Arabidopsis thaliana [Betula platyphylla [Carpinus putoensis [The response mechanism of plants to NOtions 40–0 nL·L−1 he plant . Althoughe plant , there if damage ,9, such 2 stress . In addi atrophy , lodging atrophy , etc. Adthaliana , Betula typhylla , and Carutoensis .2 stress and the comprehensive changes at different time scales. Scholars have conducted a series of meaningful explorations in studying the damage level of NO2 on different plants. For instance, researchers have examined semi-lethal thresholds for various plants and plant combinations, as well as differences in resistance between indoor and outdoor green spaces, through techniques such as spectroscopy, mass spectrometry, and nuclear magnetic resonance (NMR) [2 resistance based on apparent traits and physiological responses when studying the resistance response to a specific plant or plant group.Plants’ morphological and physiological changes can be utilized to analyze the degree of damage under NOce (NMR) ,17. Furtce (NMR)  and metace (NMR) . HoweverBougainvillea spp. is a perennial evergreen shrub belonging to the Bougainvillea genus in the Nyctaginaceae family. It is extensively cultivated in urban landscaping projects in tropical and subtropical regions due to its exceptional ornamental value and diverse potential applications. Bougainvillea has several garden advantages, including rapid growth, high organ differentiation [Bougainvillea has a certain tolerance and regulation ability to water bodies [2 pollution under laboratory-sealed fumigation conditions. At the same time, Bougainvillea also faces the negative impact of increasing NO2 in industrial and mining areas where it grows. Our research group has conducted extensive studies on the response of NO2 in Bougainvillea from 0 to 8 μL·L−1 different concentrations. The results indicated that under medium concentrations of 4 μL·L−1, Bougainvillea showed noticeable signs of injury without resulting in mortality [Bougainvillea to NO2, along with conducting systematic research and comprehensive evaluation.ntiation , and easntiation ,22. In ar bodies ,24, air r bodies ,25,26, ar bodies . It is aortality . HoweverBougainvillea to NO2. The study utilized a well-sealed experimental device to control and monitor NO2 concentration through a laboratory simulation fumigation test at a concentration of 4 μL·L−1 [2 on Bougainvillea by analyzing apparent traits, morphology and anatomical structure, water physiology, photosynthetic pigment content, chlorophyll fluorescence, and photosynthetic physiology. Furthermore, principal component analysis (PCA), membership function, and K-M survival curve were used to comprehensively evaluate the changes in various indicators under different treatments. The results of this study will further enrich the theory of plant reduction of atmospheric pollutants, expand the field of plant environmental ecotoxicology, and provide a theoretical basis for the targeted improvement of garden plant resistance and the application of NO2 management.Building upon previous research conducted by the research group, this article systematically examines the response mechanisms of 4 μL·L−1 . The inv−1 NO2 + 8 h/d) and T2 (4 μL·L−1 NO2 + 24 h/d) maintained a stable concentration throughout the experiment  and carotenoid (Car) indicators, the changes in leaves are opposite to the increase in stem and bract content. The content of total chlorophyll and carotenoids in leaves decreased significantly by 51.3% and 73.74% compared to the CK, respectively, but still significantly exceeded the chlorophyll content in stems and bracts. The changes in the content of different chlorophyll a (Chl-a) and chlorophyll b (Chl-b) organs are consistent with the total chlorophyll. Except for a significant decrease in leaves, both the stem and bracts show varying degrees of increase. The above findings suggest a reduction in leaf pigmentation and increased stem and bract pigmentation in B. glabra ‘Elizabeth Angus’ before and after treatment.Plants’ contents and proportion of pigments are important indicators for determining their apparent traits and measuring their photosynthetic potential. As shown in B. glabra ‘Elizabeth Angus’ are similar. The relative fluorescence parameters of Fo, Fv, and Vi showed significant differences under different treatments, while the differences between different treatment groups are not significant compared to Fm and Vj. Additionally, among the optical system parameters, except for Φ(Do) , all other indicators showed significant differences between treatment groups. Particularly, Φ(Eo) and ψ(Eo) of T2 decreased by 72.59% and 66.63% compared to CK, respectively. There was no significant difference between the ABS/RC, ETo/RC, and REo/RC of unit reaction center parameters, while the leaf performance index PI (ABS) showed significant differences among the treatments.Chlorophyll fluorescence is a more accurate indicator of chlorophyll concentration and photosynthetic capacity in leaves under different environments. B. glabra ‘Elizabeth Angus’ leaves at different concentrations  and the premise of principal component analysis, the requirements of a positive definite matrix and KMO test greater than 0.6 were met for each indicator. The 72 h mean values of the 50 measured indicators in the experiment were used as the baseline data , only the absolute loadings values for the Fm, Tr, and WUE indicators exceed 0.4. The ranking of comprehensive scores for the three principal components is as follows: CK (−4.135) < T1 (0.317) < T2 (3.818). The above results indicate that the stress of NO2 primarily affects B. glabra ‘Elizabeth Angus’ in changes in organ morphology and color parameters, as well as a decrease in leaf photosynthesis. Notably, CK obtains the lowest score in the comprehensive morphology index  and (2), the results  demonstrgy index .Principal component screening is conducted on 23 indicators under different treatments, and the analysis is based on fuzzy mathematical membership functions. The comprehensive scores of each indicator are determined using Formulas (3) and (4), followed by a weighted average calculation. The results are shown in B. glabra ‘Elizabeth Angus’ responds greatly under drought, saline soil, and different gas pollutants [2 significantly degraded chlorophyll in the leaves [2 and H2O, leading to the deterioration of leaf surface structure. Moreover, the leaf epidermis also demonstrates similar damage to vascular tissues induced by stress, protoplast rupture, decreased stability of intercellular structures, and impaired stomatal performance. Mature and tender leaves have poor resistance responses to stress. The environmental changes have influenced the abundance of authentic flowers in B. glabra ‘Elizabeth Angus’. Compared with previous studies, it is speculated that NO2 may impact a specific transcription factor’s regulatory activity, resulting in trait variations [2 has the potential to stimulate sexual reproduction in tomatoes [B. glabra ‘Elizabeth Angus’ [When plants are exposed to stress, the most direct manifestation is the response of apparent traits. However, plant responses are influenced by various internal and external factors, including the type and intensity of stress and plant characteristics. llutants ,28. In te leaves ,30, leade leaves , in whicriations ,33. Howetomatoes . Neverthh Angus’ ,36,37. T2 stress weakens leaf growth functional traits. Leaves, similar to other stresses, undergo self-adjustment mechanisms to effectively adapt to environmental changes [2 stress, specifically caused by the formation of nitric acid through the interaction between NO2 and plant guttation. The above results indicate that the leaves, roots, and bracts of B. glabra ‘Elizabeth Angus’ are more sensitive organs to NO2 stress. Moreover, the biochemical characteristics of the leaf surface can be utilized as indicative markers. The reduction in growth rate and the decrease in the length of internodes in real flowers and stems during periods of stress can be considered a self-protective mechanism. Considering other morphological indicators of various organs, we observed significant changes in root length, thickness, surface area, and leaf-bract color difference following stress. Meanwhile, we have found significant differences between various treatments [In this study, the majority of data collected focused on leaf indicators. However, no significant alterations were observed in leaf volume, length, width, area, or mature leaf quality. The slow or even negative increase in leaf thickness and quality in mature and tender leaves indicates that NO changes . The deceatments . Based o2, formaldehyde, and O3 stresses leads to a decline in both free water and bound water in plants [B. glabra ‘Elizabeth Angus’ under NO2 stress is moderate among the above pollution gases. The results revealed variations in water content among different organs of B. glabra ‘Elizabeth Angus’ before and after treatment. Generally, the root experiences the largest percentage decrease and serves as the primary organ responsible for water absorption. In the experiment, while NO2 did not directly enter the soil, the reduction in stem and leaf water content could enhance root water transport, thus indirectly impacting notable alterations in root apparent characteristics. However, the water content of the leaves decreased to less than 80% after stress, which is consistent with the effect observed from previous pollutants [Water is an essential requirement for the growth and development of plants. Plants’ compositions and physiological activities depend on water’s presence. Environmental conditions strongly influence the availability of water in plant tissues. Previous studies have demonstrated that exposure to SOn plants ,40, withn plants . The ratllutants .B. glabra ‘Elizabeth Angus’ were damaged, leading to a reduced capacity to utilize weak light and synthesize assimilation products. Notably, certain situations in the T1 treatment group reached their maximum values, with an observed increasing trend in the stem and bracts. This finding indirectly confirms that B. glabra ‘Elizabeth Angus’ has a certain self-regulation ability within the tolerance threshold range and tends to exhibit a passive mode of adaptation in response to moderate to high concentrations [In addition, there is a strong consistency in indicators related to plant photosynthesis, such as pigment content, fluorescence kinetics parameters, and photosynthetic indicators ,42. The trations .2 stress at concentrations of 12 mg·m−3 and 4 μL·L−1 resulted in an increase in Fo and a subsequent reduction in Fv/Fm of photosystem II in Bougainvillea spectabilis and Carpinus turczaninowii, respectively [2 at a concentration of 4 μL·L−1. Generally, higher initial fluorescence Fo indicates stronger stress and adversity for plants, whereas Fm and Fv exhibit the opposite trend. The changes in the three indicators in this study were similar and consistent with the initial predictions [Vi and Vj represent the relative variable fluorescence intensity at points I and J, respectively, which are significant indicators of the OJIP curve. The varying degrees of increase in these two indicators at T1 and T2 suggest that the fluorescence curve of B. glabra ‘Elizabeth Angus’ has undergone adjustments to adapt to the environment. The increase in Vj during T1 treatment is less than Vi, indicating that the transmission of electrons from QA to QB is blocked. The accumulation of electrons in QA indicates that the damaged site is within QA [Chlorophyll fluorescence and photosynthetic parameters can effectively reflect real-time photosynthesis and potential capacity in plants. Previous studies have shown that exposure to NOectively ,18. Thisdictions . Vi and ithin QA .Φ (Po), Fv/Fo, and Φ (Do) represent the maximum quantum yield of photosystem II, the potential quantum yield, and the maximum quantum yield of non-photochemical quenching, respectively. The significant changes between different treatments indicate that the PSII photosystem is disrupted under stress conditions in the triangular plum. The absorption of light energy by the unit reaction center ABS/RC has increased, but there has been a decrease in ETo/RC for electron transfer energy and REo/RC for light energy transferred to PSI, which suggests that the absorbed energy by the reaction center has not been effectively transmitted to the receptor site for physiological reactions. The PIABS) and the transpiration rate (Tr) observed in the photometric indices aligns with the anticipated outcomes [−1 typically reduces photosynthetic rate among most plant species [Optical system parameters outcomes . However species .−1 ± 0.1 μL·L−1. In contrast to formaldehyde and dust, NO2 is a gas with dualistic properties. On one hand, fumigating plants with NO2 does not inhibit or stimulate plant growth in a short period. This phenomenon is known as the “activation effect”, characterized by NO2 compensation points [Arabidopsis thaliana at low concentrations (<1 μL·L−1), the leaf area exhibits a notable increase [In this study, a mass flow controller and cloud platform were employed to monitor data and effectively maintain the gas concentration in the laboratory at a range of 4.0 μL·Ln points . For exaincrease .2, as a signaling molecule, also has adverse effects on plant metabolism. Therefore, research on the semi-lethal concentration of NO2 has demonstrated that plants should not endure it for more than 48 h when exposed to a concentration of 8 mg·m−3 [B. glabra ‘Elizabeth Angus’ treated with T1 could recover by replacing damaged, mature leaves with tender leaves, while there was no similar renewal phenomenon under T2 treatment.On the other hand, NOB. glabra ‘Elizabeth Angus’. This finding demonstrates similarities between the composite gas experimental studies conducted on highways in India and Egypt [B. glabra ‘Elizabeth Angus’ through exogenous active substances [The Kaplan-Meier (K-M) curve is commonly used to analyze changes in overall survival status between the treatment and control groups in the presence of a specific toxic effect. The statistical results of the proportion of undamaged leaves in this study showed that the expected gradient (CK > T1 > T2) was observed. During the 72 h of continuous pollution, damaged leaves had a median survival time of 41 h. Furthermore, the HR (hazard ratio) for the intermittent fumigation was only 0.3735, significantly lower than the mortality rate observed with continuous fumigation (T2). The 23 indicators selected in PCA are more effective in representing the main influencing factors and their respective weights. Indicators showing significant differences among different groups are more frequently observed in the final load matrix. Among them, root, leaf color, bract color, and chlorophyll fluorescence indicators can be the primary indicators to assess the resistance and adaptability of nd Egypt ,50. The bstances ,52,53.2 airtight fumigation test on the resistant variety B. glabra ‘Elizabeth Angus’ using three treatments. The results indicated that NO2 concentration of 4 μL·L−1 caused significant damage to the PSII photosynthetic system and apparent traits of B. glabra ‘Elizabeth Angus’, which resulted in the inactivation of the root system and reduced its water absorption capacity by harming the root structure. Decreasing the concentration of photosynthetic pigments and water in leaves and bracts leads to a lighter and yellowish color and the erosion of vascular tissue and epidermis by nitric acid. In addition, the photosynthetic capacity of the PSII photosynthetic system within the leaves was continuously disrupted and declined. There were no significant changes observed in the stem and floral organs. Additionally, the opening of the real flower corolla tube was found to be closed under NO2 induction. K-M survival curve analysis was conducted continuously for 72 h. The median survival time of 4 μL·L−1 fumigation was 41 h. Root and leaf Lab color differences, chlorophyll fluorescence, and Pn can be utilized as stress indicators.In summary, this study conducted a 72 h NOBougainvillea glabra ‘Elizabeth Angus’ were purchased as cuttings from the Xiaxi Flower and Wood Market in Changzhou in September 2022 , clean air for other times; T2: 4 μL·L−1 NO2 for all days inside the box (4 μL·L−1 NO2 + 24 h/d). At the same time, set the control group CK: clean air (0 μL·L−1) in the box all day long (0 μL·L−1 NO2 + 24 h/d). Ten plants were used per treatment, with a total of 3 replicates in a treatment. For the experiment, the test gas was sourced from Nanjing Changyuan Industrial Gas Co., Ltd. , with a gas concentration of 4 μL·L−1. The gas concentration in the fumigation box was controlled by the ALICAT MC mass flow controller (1 sccm = 1 mL·min−1) with a concentration of 4.0 μL·L−1 ± 0.2 μL·L−1. In short, each box is taken for fumigation for approximately 315 s  and subsequent gas replenishment. Detector and real-time concentration data cloud platform were provided by Weihai Jingxun Tongtong Electronic Technology Co., Ltd.   B. The fuB. glabra ‘Elizabeth Angus’ were measured at 08:00 every day . The length and thickness of the main and lateral stems, ground diameter (diameter 5 cm above the base of the plant), plant height (height from base to top bud) A, and crB. glabra ‘Elizabeth Angus’ leaves.The root system, branches, petiole transverse structure, leaf surface structure, bract surface structure, and floral organs  were examined by immersing the sampled sections in water. Temporary slides were observed under an optical microscope , and photographs were collected. The specific process of leaf microstructure sampling and observation is as follows: the test plant leaf was bladed to take a number of small pieces of 5 mm × 5 mm, quickly submerged in 2.5% glutaraldehyde solution, then fixed with osmium acid at 4 °C for 24 h, rinsed three times with phosphate buffer (pH = 7.2), and sprayed after the dehydration process had reached the critical point, and a scanning electron microscope (SEM)  was used to observe and photograph the front and back surfaces and sections of The process of observing the ultrastructure of leaf organelles was basically similar, and a number of small pieces of 2 mm × 2 mm leaves were cut with a knife and quickly submerged in 2.5% glutaraldehyde solution, rinsed three times with phosphate-buffered solution (pH = 7.2), and dehydrated and then embedded in 100% embedding agent. After immersion for 24 h, the embedded sections were stained, then observed and photographed by transmission electron microscopy (TEM) (JEM−1400).The sampling sites for measuring water and pigment content in various organs are consistent. The roots were the cuttings’ primary roots, the primary lateral stem on the cutting main stem, the fully functional leaves located from the top of the branches to the 3rd to 5th segments below, and the bracts were the mature bracts. The procedure for determining the water content of various organs and tissues under different treatments is as follows: Once fumigation is finished, any surface moisture and dust on each organ are eliminated using dry paper, and then the fresh weight (FW) is measured using an electronic balance. Then, the fresh weight (FW) is subjected to thermal treatment at 105 °C for 0.5 h in an oven, followed by drying to a constant weight at 65 °C. The dry weight (DW) is measured, and the relative water content ((RWC) = (FW − DW)/FW) and specific leaf area (SLA) are calculated. The method for determining the content of chlorophyll is as follows: For each organ sample, the surface is carefully rinsed with deionized water. Then, 0.2 g of the sample is weighed and soaked in 5 mL of a 95% ethanol solution under dark conditions until the sample completely changes to white. The blank control was prepared using 95% ethanol. Enzyme-linked immunosorbent assay measured the optical density (OD) values at 665, 649, and 470 nm for various sample extracts. Each sample was repeated three times to obtain the average value. The content of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in the samples was then calculated using the corresponding absorbance value formula sequentially [Fo), maximum fluorescence (Fm), variable fluorescence (Fv), the point I relative variable fluorescence (Vi), point J relative variable fluorescence (Vj), photosystem II maximum quantum yield (Φ(Po) = Fv/Fm) and the other form (Fv/Fo), electron transfer quantum yield (Φ(Eo)), the capture of light energy for energy ratio for electron transfer (ψ(Eo)), electron reduction efficiency at the PSI acceptor side end (Φ(Ro)), maximum quantum yield for non-photochemical burst (Φ(Do) = Fo/Fm), absorbed energy (ABS/RC), energy used for electron transfer (ETo/RC), light energy for transfer to PSI (REo/RC), and performance index based on absorbed light energy (PIABS). Measurements were conducted daily from 08:00 to 09:00 a.m. The instrument used for measurement was a HandyPEA high-speed continuous excitation fluorometer with a light intensity of 3000 μmol·m2·s−1, a light source of 630 nm red light, and a recording interval of 2 s. The leaves were dark-adapted using leaf clips for 30 min before measurement. Each plant was selected from the top to the bottom of 4–6 nodes of the main branch with the same sunny leaf, and each functional leaf measurement was repeated 3 times, and the average value was obtained.The measured chlorophyll fluorescence parameters include initial fluorescence (2 concentration (Ci), stomatal conductance (GS), transpiration rate (Tr), water utilization (WUE), and water vapor pressure deficit (VPD)) were measured by a CIRAS-3 photosynthesizer. The photosynthetic indexes were measured between 9:00 a.m. and 11:00 a.m. on a clear and windless morning. Three sunny mature leaves from the top to the bottom 4–6 nodes of the main branch were selected from each plant for measurement. Each measurement was repeated three times. The measurements were conducted under consistent conditions, including a leaf chamber temperature of 25 °C, a leaf chamber relative humidity of 75%, and CO2 concentration (380–420 μmol·mol−1). The photosynthetically active radiation parameter (PAR) was also set to 1000 µmol·m−2·s−1.Photosynthesis-related parameters (net photosynthetic rate (Pn), intercellular COp < 0.01, p < 0.05). All data were the mean ± standard error (Mean ± SE) of 3 replicates.Experimental data were processed using Excel 2016. Charts were generated using GraphPad Prism 9 and Origin software. Statistical analysis was conducted using SPSS 25.0 software for One-Way-ANOVA, and the data was analyzed using Tukey Multiple Comparisons for inter-group significance (In principal component analysis, the data are pre-standardized using SPSS, and the Fn and F values for different concentration treatments are calculated using the cumulative contribution rate weights and eigenvalues of the principal components.ij is the weight of each variable in the principal component, θj is the corresponding variable coefficients in the component matrix, and max and Xmin, respectively, represent the minimum and maximum values in a certain indicator [Principal component analysis and the membership function were referenced separately, and the key formulas were provided below:ndicator .2 on B. glabra plants and systematically evaluate their resistance, materials with higher resistance in this genus were selected. In this study, the effects of different durations of fumigation with NO2 fumigation at a concentration of 4 μL·L−1 on the apparent traits, morphology, anatomical structure, water physiology, photosynthetic pigment content, chlorophyll fluorescence, and photosynthetic physiology of B. glabra ‘Elizabeth Angus’ were investigated. After evaluating the results under different treatments through principal component analysis, membership function analysis, and K-M survival curve analysis, we conclude that exposure to a high concentration of NO2 at 4 μL·L−1 for 72 h led to weakened root function, diminished color in the leaves and bracts, reduced chlorophyll content in the stems, and damage to the PSII photosystem, and a decrease in Pn, Tr, and WUE in photosynthetic physiology. During the K-M survival time analysis, the median survival times of the undamaged leaves were determined to be 41 h and 55 h for the 8 h/day and 24 h/day fumigation treatments, respectively. However, the 8 h/day treatment seedings recovered to a certain extent by forming new tender leaves during subsequent regeneration. Prolonged exposure to 4 μL·L−1 of NO2 can result in irreversible damage to B. glabra ‘Elizabeth Angus’, primarily characterized by decreased organ morphological parameters and reduced leaf photosynthesis. Root volume, average root diameter, leaf Lab color difference indicators, chlorophyll fluorescence parameters, net photosynthetic rate, and fumigation time are closely related and can be used as crucial evaluation indicators for the resistance of B. glabra ‘Elizabeth Angus’ to NO2 stress. This study conducted a comprehensive analysis and evaluation of the morphological characteristics and physiological responses of B. glabra ‘Elizabeth Angus’ under a resistance of 4 μL·L−1, thus revealing the response mechanism of B. glabra ‘Elizabeth Angus’ under medium to high concentrations of NO2 stress. The results of this study are conducive to expanding the field of plant environmental ecotoxicology and providing a theoretical basis for the targeted improvement of garden plant resistance and the application of plant NO2 reduction.To investigate the damage mechanism of NO


MUC6), growth (ADAMTSL3), and adaptability (EBF2). Our analysis has provided numerous genomic characteristics of some Chinese cattle breeds, which are valuable as customized biological molecular markers in cattle breeding and production.Qaidam cattle (CDM) are indigenous breed inhabiting Northwest China. In the present study, we newly sequenced 20 Qaidam cattle to investigate the copy number variants (CNVs) based on the ARS-UMD1.2 reference genome. We generated the CNV region (CNVR) datasets to explore the genomic CNV diversity and population stratification. The other four cattle breeds  from the regions of North China embracing 43 genomic sequences were collected and are distinguished from each of the other diverse populations by deletions and duplications. We also observed that the number of duplications was significantly more than deletions in the genome, which may be less harmful to gene formation and function. At the same time, only 1.15% of CNVRs overlapped with the exon region. Population differential CNVRs and functional annotations between the Qaidam cattle population and other cattle breeds revealed the functional genes related to immunity ( Bos Taurus) and humped indicine (Bos Indicus)  , 2. MoreIndicus) .Bostaurus) into the present-day Qinghai and Gansu Provinces of China during a southward invasion, which might have influenced the breeding herds of the present Qaidam cattle. Paternal and maternal diversity studies indicated that Qaidam cattle included two lineages  are defined as the deletion or duplication of a genome copy number, ranging from 50 bp to several Mb in length . As compIn the present study, we performed a genome-wide CNV analysis using genomic resequencing data in six Chinese cattle breeds. The purpose was to generate a comprehensive CNV landscape in Qaidam cattle to investigate and compare the diversity and population–genetic properties of the CNV regions (CNVRs) among them and to explore the diverse selection patterns involved with the CNV genes for local adaptation in Chinese native cattle.Figure 2A).Qaidam Basin is the highest basin in China with an altitude of 2,600–3,000 m and is located in the northwest region of the Qinghai Province and the northeast region of the Qinghai–Tibet Plateau. The climate of the basin is characterized as extremely dry and cold, with an annual average precipitation of <200 mm and an annual average temperature of ~3.0–6.5°C. To reflect the sample representativeness of the Qaidam cattle, 20 samples were collected from five different counties/cities  in the Qaidam Basin . Moreover, 42 publicly available data of four Chinese cattle breeds were downloaded in this study  . It is wB. taurus reference assembly (ARS-UCD1.2) using the Burrows–Wheeler Aligner (BWA) program with default parameters  was used to stratify and cluster the close breeds/populations, which plays a positive role in understanding the genetic differences among cattle subpopulations. According to the smartPCA module of EIGENSOFT (Program 2006), the PCA calculation was performed based on the four different CNVR datasets.VST /VT, where VT represents the variance among all the unrelated individuals and VS is the average variance within each population, weighted for population size  to discover autosomal CNVs among individuals relative to the ARS-UCD1.2 reference genome. We generated the CNVR datasets from each cattle breed. The CNVR set contained 10,178 CNVRs, which were detected from 63 cattle genome datasets. There were 5,743 duplication CNVRs; 4,187 deletion CNVRs; and 248 both duplication and deletion CNVRs . Here, 1Bos taurus. A principal component analysis (PCA) was carried out with an obvious distinction from deletions  and other cattle breeds from the regions of North China   –7. Firstp = 4.49 × 10−7), “Pi3k-akt signaling pathway” (p = 1.82 × 10−8), “mTOR signaling pathway” (p = 3.22 × 10−6), “HIF-1 signaling pathway” (p = 4.95 × 10−5), and “aldosterone-regulated sodium reabsorption” (p = 5.91 × 10−4)  in the study (p =2.73 × 10−4), “calcium signaling pathway” (p =2.69 × 10−3), “GnRH signaling pathway” (p = 0.01122), and “insulin signaling pathway” (p = 0.04588)  deserved more attention in copy number between CDM and MG (p = 5.48 × 10−6) and “ErbB signaling pathway” (p = 7.49 × 10−5)  were noteworthy in copy number between CDM and XZ (p = 1.10 × 10−3), “Salmonella infection” (p = 0.02195), and “human immunodeficiency virus 1 infection” (p = 0.02446)  were notable in copy number between CDM and HSK  . There whe study . The sel0.04588) . Among tM and MG . The sel × 10−5) . Among tM and XZ . There w0.02446) . Among t and HSK .Bos Taurus, Bos Indicus, and their crossing populations.During domestication and diversification, the frequency of copy number variation in the species' genome responds to selective pressure. Considerable effort has been applied to identify the causal mutations and genes. However, screening the selected genomic copy number genetic markers is complex. Over the past decades, high-throughput sequencing techniques and bioinformatics tools have been increasingly used to construct genome-wide CNV maps , 17, 18.In our study, we investigated the CNV of 20 newly resequenced Qaidam cattle genomes based on the ARS_UCD 1.2 cattle reference genome. It improved the reliability of screening CNVs more than through UMD 3.1 assembly , 20. A tEBF1 and ZNF521 related to fat development ” ” ” , and was014482)” . A previigestion . Specifie genome . A previronments . Structu-glycans . In rumisistance , 30. ThePRKCA, CAMK2D, PHKB, and GRID2 genes  were related to muscle growth and development by searching previous research studies  was associated with body weight for pre-weaning growth in Esme sheep  were significantly associated with body size traits  can be found in the article/The animal study was reviewed and approved by the Institutional Animal Care and Use Committee of Qinghai Academy of Animal Science and Veterinary Medicine, Qinghai University. Written informed consent was obtained from the owners for the participation of their animals in this study.YL drafted the manuscript and took part in the analysis of genome data. ZM, CL, and XW contributed to the sample collection. WW and YM performed the primary analysis of genome data. ZA and ZM revised the writing. ZM and CL designed the experiment and provided the funding for this research. All authors read and approved the final manuscript.