The oxidationof organic films at the surface of atmospheric aqueous aerosols caninfluence the optical properties of the aerosol and consequently canimpact Earth’s radiative balance and contribute to modern climatechange. The amount of material at the air–solution interfacewas found to decrease on exposure to aqueous-phase radicals whichwas consistent with a multistep degradation mechanism, i.e., the productsof reaction of the DSPC film with aqueous radicals were also surfaceactive. The multistep degradation mechanism suggests that lipid moleculesin the thin film degrade to form progressively shorter chain surfaceactive products and several reactive steps are required to removethe film from the air–solution interface. Bimolecular rateconstants for oxidation via the aqueous phase OH radical cluster around1010 dm3 mol–1 s–1. Calculations to determine the film lifetime indicate that it willtake ∼4–5 days for the film to degrade to 50% of itsinitial amount in the atmosphere, and therefore attack by aqueousradicals on organic films could be atmospherically important relativeto typical atmospheric aerosol lifetimes.Neutron reflectometryhas been used to study the radical initiatedoxidation of a monolayer of the lipid 1,2-distearoyl- A coated aerosol could be oxidized from the gaseous phaseabove the film, i.e., from the “top-down”,35 or from the aqueous phase below the film, i.e., from the “bottom-up”.Oxidation from the “bottom-up” has been shown for solidfilms and radicals generated from the solid phase.43 Karagulian et al.43 studiedthe oxidation of a solid monolayer of the lipid 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC) coated on a mixture ofNaNO2 and NaCl. OH radicals were formed on illuminationof the system, and oxidation of the OPPC film was observed using diffusereflection infrared Fourier transform spectrometry (DRIFTS) and matrixassisted ionization mass spectrometry (MALDI). The study suggestedthat similar reactions could also occur for aqueous aerosols coatedwith an organic film. Jones et al.44 usedX-ray reflectivity to study the oxidation of atmospheric films usingmaterial extracted from atmospheric filter samples at the air–solutioninterface and conducted experiments from the “bottom-up”using the aqueous phase radicals OH and nitrate radical to demonstratethat the atmospheric film was susceptible to aqueous reaction.Atmospheric oxidants exist in both the gaseous and aqueous phase;common gas phase oxidants include ozone,sn-glycero-3-phosphocholine(DSPC) by the common cloudwater aqueous phase radicals, hydroxyl (•OH),48 sulfate (SO4•–)41 and nitrate (NO3•),49 was performed. The reactions were probedby a series of neutron reflectometry experiments using films spreadon the surface of solutions in a Teflon trough.It is known that aqueous cloud processes oxidize thin films, butlittle is known about the kinetics. Therefore, in order to assessthe importance of aqueous-phase oxidation of thin films and to determinethe film lifetime with respect to oxidation, the investigation ofthe aqueous phase oxidation of a well-defined organic film of thelipid 1,2-distearoyl-52 In the present work, neutron reflectometry was used to follow thesurface coverage and estimate the thickness of the films at the air–solutioninterface as they react. Previous neutron reflectometry studies havebeen successfully conducted on the gas-phase oxidation of atmosphericallyrelevant monolayers at the air–water interface.55 X-ray reflectivity has also been used to study thesusceptibility of real atmospheric films44 to oxidation from the gaseous and aqueous phase. The lipid DSPCwas chosen for the current study as it is a naturally occurring phosphocholinelipid that forms organic films57 with a well-known chemicalstructure and is therefore well suited to kinetic studies.Neutron reflectometryis a surface reflection technique that canprovide information about the physical properties of molecular monolayersand reaction kinetics at the air–solution interface.Thefollowing aqueous phase reactions were studied using neutronreflectometry to follow the decay of material (DSPC film and resultantproducts) at the air–solution interface:The oxidative loss of DSPCfrom the air–solution interfacewas subsequently kinetically modeled to reproduce the surface coverageas a function of reaction time. A bimolecular rate constant was determinedfor the loss of surface-active material at the air–solutioninterface, thus allowing the calculation of a film lifetime with respectto radical oxidation in the atmosphere. Comparison of the film lifetimewith typical atmospheric aerosol residence times allows the importanceof such aqueous phase radical reactions to be assessed and informson whether such reactions should be included in atmospheric and aerosol/cloudmodels.The section described here includesan introduction to neutronreflectometry and the associated experimental setup used in the neutronreflection experiments. An explanation of aqueous radical generationis provided as well as a description of the calculation of the radicalsteady-state concentration.50 Specular neutron reflection allows the determinationof the neutron refractive index profile normal to the air–solutioninterface.51 The reflectivity of the filmcan be modeled and compared to experimental data to obtain informationon the amount and thickness of material at the air–solutioninterface.Neutron reflectometrywas usedto study a monolayer film at the air–solution interface.58 and at the InstitutLaue-Langevin (ILL), Grenoble, France, using the FIGARO reflectometer.59 At ISIS, neutron reflection was recorded atan angle of 1.5° to the horizontal using a wavelength range of0.5–6 Å. At the ILL, neutron reflection was recorded atan incident angle of 0.62° to the horizontal with a wavelengthrange of 2–20 Å and at an incident angle of 3.8°to the horizontal with a wavelength range of 2–30 Å.Measurements were made at the ISIS neutron sourceat the Rutherford Appleton Laboratory, Oxfordshire, UK, using theSURF reflectometer50 and therefore will only be described brieflyhere. Neutron reflectivity, R, is measured as a functionof the momentum transfer, Q, of the neutron58 where Q is defined asThe application of the neutron reflection technique to speciesat the air–water interface has been described by Lu et al.50 for a monolayerof deuterated material at the air–water interface is approximatelygiven by51 definedasb is the neutron scatteringlength of a nucleus and n is the number density ofthat element.48 The value of b for fully deuterated DSPC (C44H5NO8PD83) used in this study is 888.34 fm based on valuesof b for individual elements.60 The reflectivity data were normalized using the intensityspectrum of the direct beam of neutrons, and the absolute reflectivitywas determined using a scale factor obtained from measuring the reflectivityof pure D2O in the trough.Neutron reflectivity60 where b dependson the interaction between the nucleus of an atom and a neutron.61 The difference in bound coherent scatteringlength between hydrogen and deuterium is distinct, b = −3.74 fm for hydrogen and b = 6.67 fmfor deuterium, whereas the chemical properties are the same. Specificchemical moieties of a molecule can be selectively deuterated in orderto highlight the deuterated parts by producing a strong contrast betweenthe film, subphase and air.50 The subphaseis the medium below the film, i.e., the monolayer film to be studiedis spread on top of the subphase, a radical precursor solution inthe experiments described here. In our study, the reflectivity ofthe film was increased relative to the air and subphase by using fullydeuterated DSPC (C44H5NO8PD83) in order to achieve a large scattering length density  in comparison to that of the subphase. The subphase had a scatteringlength density of zero (effectively the same as the air above thefilm) and was therefore null reflecting. A solution of so-called nullreflecting water (NRW) consists of D2O and H2O in the volume proportion 8.1% and 91.9%, respectively. In the currentexperiment, aqueous radicals were generated photolytically from thesubphase, and consequently, the volume ratio of D2O andH2O in the subphase was slightly adjusted to account forthe scattering length density of the radical precursor chemicals toachieve an overall value of zero scattering length density. A monolayerof fully deuterated DSPC was spread on top of the null reflectingradical precursor subphase contained in the trough, and the specularneutron reflection signal was dominated by reflection from the monolayerfilm. Neutron reflectometry measures the combined amount of reactantand any insoluble, involatile, surface-active reaction product thatremains at the air–solution interface, meaning it is a convolutionof the remaining reactants and any products that have not yet dissolvedor evaporated.Isotopes of the same elementtypically have different neutron scatteringlengthsQ was typically recorded continuouslyin intervals of 300or 900 s . Each kinetic run monitoring 63 which allows determination of the scattering length densityand thickness of the deuterated material at the air–solutioninterface.In the current study, neutron reflectivity asa function of b, of a moleculeof a film composed entirely of the same molecule, and its surfacecoverage, Γ, by35b, is not constant in a reactingsystem where the molecule does notleave the air–solution interface, and a mixture of differentproduct molecules may also be present at the air–solution interfacewith different neutron scattering lengths, contributing to the overallneutron reflectivity. Therefore, the scattering length per unit area,ρδ, of all of the material at the air–solutioninterface is kinetically followed as a function of time, ρtδt. Askinetics is the focus of the present study, the quantityt=0δt=0 is the product of the scattering length density and filmthickness at time zero.Scattering length density ρ, and film thicknessδ,can be related to the scattering length equationE to individual molecular components making up the film withtime, the weighted sum of the individual products of scattering length, b, and surface coverage, Γ, for each component needto be considered.As will be detailed in the 64 was usedto reproduce theexperimental reflectivity data.MOTOFIT2 and a liquid depth of approximately3.5 mm was used in the study. UV lamps were suspended above the troughalong its length to photolytically generate the radicals and providean even illumination of the air–solution interface. Two typesof UV lamps were used, black lamps centered at wavelength ∼360nm (UVP) to generate SO4•– and NO3• radicals and germicidallamps that provided a significant output at ∼254 nm (UVP) togenerate •OH radicals. In both cases, the bulbswere situated in a retroreflector within the lamp body at a fixedheight above the air–solution interface. The trough and lampswere loosely surrounded by a Tedlar plastic film to keep the interfacefree from dust.A custom PTFE trough with an areaof of 240 × 70 mm44H5NO8PD83), >99% atompurity,from Avanti Polar Lipids Inc. was spread on the surface of the radicalprecursor aqueous subphase as a 1 mg mL–1 solutionin chloroform using a glass microliter syringe. In each experiment, 40 μLwas typically added to the air–solution interface. Previouslyit had been determined that 40 μL provided a surface pressureof ∼20 mN m–1 on the trough used in theseexperiments. Surface pressure was not measured during the neutronstudies because UV radiation degrades the tensiometer and would haveblocked the neutron beam on the small trough used to achieve evenillumination from the photolysis lamp. Neutron reflectivity as a functionof momentum transfer, Q, was recorded before andduring photolysis of the subphase to monitor the change in the DSPCmonolayer.59A monolayer of fully deuterated DSPC  and placed at a height of ∼83mm above the trough. A clean well-established method of producinghydroxyl radicals as demonstrated by Karagulian et al.43Aqueous radicals were photolyticallyproduced from the subphase using aqueous phase photochemistry.–3 aqueous solutionof K2S2O866 using four black bulbs centered at ∼360 nm (UVP) at a heightof 128 mm above the trough.Sulfate radical anions were generatedby photolysis of a 0.03 mol dm–3 K2S2O8 and 0.1 mol dm–3 KNO3 by the method of Herrmann,26 using fourblack bulbs centered at ∼360 nm (UVP) and placed at a heightof 128 mm above the trough at ISIS and 115 mm above the trough atthe ILL. The height of the lamps was used to control the flux of photonsand associated rate of reaction. Photolysis of S2O82– yielded two SO4•– radicals as detailed in 4•– with an excess of NO3– resulted inthe production of the nitrate radical, NO3• as described by Herrmann.26Nitrate radicals were generated byphotolysis of an aqueoussolutionsubphase containing 0.03 mol dm69 The concentration of the aqueous radical precursorwas chosen to maintain a constant steady-state radical concentrationthroughout the entire kinetic run. The focus is on the radicals generated,not the radical precursors used, with the only requirement being thatthe precursors do not interfere with the reaction.The UV lamps used to initiate photolysiswere switched onand offremotely and produced a stable irradiance after 3 min.–3 KNO3, 0.03mol dm–3 K2S2O8 with 0.1 mol dm–3 KNO3, and 0.03 moldm–3 K2S2O8 and“light or photolysis controls” conducted with UV lighton a monolayer of DSPC on null reflecting water with no radical precursorspresent.Two setsof control experiments were performed, “dark controls”conducted without UV light on a monolayer of DSPC on the aqueous solutionsubphases of 0.03 mol dm•OH, NO3• or SO4•–) is strictly a determination ofthe “bulk” concentration of radical. The very largeexcess of the photolabile radical precursor (NO3– and S2O82–) should preventa reduction in the radical concentration near the air–solutioninterface owing to reaction.Two kinetic models were developedin the work presented here: a multistep degradation of material atthe air–solution interface and a steady-state analysis of theradical concentration. The secondary chemistry following photolysisrequired determination of the steady-state concentrations of hydroxylradicals and sulfate radical anions by kinetic modeling as describedbelow. It was not possible to attempt the same analysis and modelingwith the nitrate radical as the secondary chemistry is not accuratelyknown. Note that the steady-state analysis of the radical concentration was kept large to maintain an effectivelyconstant concentration of radical precursor and thus a constant concentrationof radical in steady-state concentration throughout the reaction.However, in order to calculate the photolysis rate constant for NO3– and S2O82– the precursor solutions were photolyzed at smaller concentrationsof 0.0003 mol dm–3 KNO3 aqueous solutionand 0.0003 mol dm–3 K2S2O8 aqueous solution to observe and model the loss of radicalprecursor. Loss of KNO3 or K2S2O8 was followed by UV–visible spectrometry for up to10 h for K2S2O8 and up to 16.5 hfor KNO3. The following photolysis reaction schemes werekinetically modeled using a Backward Differentiation Formula (BDF)method to handle stiff systems,72 and the value of the appropriatephotolysis rate constants, J, was varied until themodeled temporal variation of the concentrations of NO3–, NO2– and S2O82– fitted the experimentallydetermined temporal profile of the concentrations. Rate constantsfor the reactions in the photolysis schemes were obtained from theliterature where possible, and the following rate constants were determinedfrom kinetic modeling: J4, J5, J7, J11, and k12.The steady-state concentrationswere measured in a series of off-lineexperiments. The loss of radical precursor was measured as a functionof photolysis time to determine the photolysis rate constant, J4 = 3.5 ×10-6 s–1J5 = 3.5 ×10-6 s–1k9 = 1.3 ×108 M–1 s–173k10 = 6.0 ×109 M–1 s–174J11 = 5.0 ×10–5 s–1k12 = 1 s–1k13 = 6.0 ×109 M–1 s–174k14 = 0k15 = 4.2 ×107 M–1 s–175k16 = 0.5 M–1 s–175k17 = 6 ×109 M–1 s–175k18 = 980000 M–1 s–175k19 = 1.0 ×1010 M–1 s–175k20 = 1.5 × 1010 M–1 s–165k21 = 1.1 ×109 M–1 s–165k22 = 530 s–165k23 = 4.5 ×108 M–1 s–165k24 = 1000 s–165k25 = 1.3 ×109 M–1 s–165k26 = 1.4 s–165Hydroxyl radicalsare produced from the photolysis of nitrate from the following photochemistry:3– and NO2– anions were measured by UV–visiblespectrometry over the wavelength range ∼200–500 nm ina long path length liquid cell (17.5 cm) for a series of photolysistimes from 2 h up to 16.5 h. The steady-state concentration of •OH radicals was then determined from kinetically modelingthe above reactions  was used to calculate the sulfate radical steady-stateconcentration in the neutron experiments as 4.7 × 10–11 mol dm–3.Owing to the weak absorptionof the SOTable S2).It was noted that light attenuationby the water or aqueous radicalprecursor solution could occur at 254 or 360 nm; however, light attenuationwas found not to be an issue following an e-folding depth calculationas detailed in the Supporting Information  to decrease and be measured in order to determine the photolysisrate coefficients of the precursor species. In some aspects the offlinesteady-state determination experiments are similar to a traditionalactinometry experiment76 but using thecompound of photolysis as the actinometer.The steady-state concentrations of reactant radicals listed in ants eqs , and R11ants eqs , and R1177 was fitted to the experimentally determined decrease in surfacecoverage of material with time at the air–solution interface.The characteristic temporal profile and lack of exponential decayled to consideration of a multistep degradation mechanism. The followingmechanism is proposed:(surf) is amonolayerof DSPC at the air–solution interface; X•(aq) is an aqueous radical oxidant ; A(surf), B(surf) and C(surf) aresurface active deuterated products at the air–solution interface;and D(aq) is a deuterated product that is not surface-active,i.e., A, B, and C reside at the air–solution interface whereasproduct D partitions irreversibly to either the gas-phase or the aqueoussubphase. Experimentally determined surface coverage was defined asthe weighted sum of the surface coverage of all proposed deuteratedproduct species at the air–solution interface including theoriginal DSPC film and any other deuterated surface-active productsthat may have formed from reaction with the radical species, i.e.,products A–C. Each proposed surface-active product (A–C)has a scattering length density that is consistent with oxidationremoving parts of the original DSPC molecule . To estimate the possibilityof such a process would require repeating the experiments, stoppingthe oxidation (by switching off the photolysis lamps) at periodicparts of the reaction, and observing/measuring any further loss ofmaterial.The concentration of the radicals [X]in the vicinity of theair–solutioninterface are in steady-state during the reaction, i.e., d[X]/d3•, SO4•–, and •OH, respectively. The experimental data are reproduced by calculationof k36′–k39′ usingkinetic modeling. k′ foreach degradation step for each radical system (•OH and SO4•–).78 Individual amounts of the modeled surface-activedegradation products A, B, and C are also shown in A simpleexponential decay has been fitted to the photolysis control(red squares) in k′ that provideda reasonable fit by eye was ±5% for the hydroxyl system, ±10%for the sulfate system, and ±20% for the nitrate system. Forthe nitrate system, a further sensitivity analysis was performed;each pseudo-first-order rate constant was varied individually by 10%and the remaining rate constants were subsequently adjusted to maintaina good fit through the data points. From variation of individual pseudo-first-orderrate constants, it was deemed that no one rate constant was more orless significant in determining the reaction profile.The pseudo-first-order and bimolecular rateconstants reportedin 84 The characteristic time fortransport of OH radicals to the interface is d = 2.5nm (theapproximate size of the DSPC molecule at the air–water interface62) and an estimate of the diffusion coefficient D = 2.8 × 10–9 m2 s–185 gives ∼0.2 ns.The characteristic reaction time is k = 3.5 × 10–4 s–1 taken from 87 is thus not considered. The photolytic source of OH radicals froman enormous excess of nitrate anions was chosen to prevent a diffusiveconcentration profile from building up to the interface over the courseof the long reaction time.The diffusionof OH radicals to the interface was not consideredto be a slow process relative to the rate of loss of OH radicals owingto reaction with the film. Characteristic time scales for diffusionand reaction can be estimated from simple formulas in Finlayson-Pittsand Pitts.•OH radical attack arelarger than the bimolecular rate constants determined for oxidationinitiated by aqueous phase sulfate radical attack. Comparable valuesof bimolecular rate constants were determined in recent studies foraqueous phase •OH radical reactions with cis-pinonic acid (∼3–4 × 109 M–1 s–1) and substituted phenols(on order of 109 M–1 s–1 to 1010 M–1 s–1 dependingon the specific phenol and the pH).90 The subsequent bimolecularrate constants for each step of the degradation mechanism are similarto each other, which is what is expected given that A, B, and C willhave similar reactivity toward OH radical, i.e., the radical abstractsa deuterium from DPSC, A, B, and C.The bimolecularrate constantsdetermined for each step in the degradation mechanism eqs –R39 of a78 but the kinetic isotope effect is generally a factor of 6.1 forbreaking a C–H bond.78 The rateconstants have not been corrected for the kinetic isotope effect,and thus, the values in Note that owing to the deuterationof the DSPC film for the neutron reflection technique, there willbe a potential kinetic isotope effect on the values of the rate constants.Statistical mechanics has shown the kinetic isotope effect to be upto a factor of 7.2 for hydrogen abstraction,44 however, an increasing numberof recent studies focus on aqueous phase oxidation in the bulk101 and in particular by the aqueous phase OH radical.101 Other relevant studiesinclude that of Sarang et al.,97 who consideredaqueous phase oxidation of so-called “Green Leaf Volatiles”,unsaturated oxygenated hydrocarbons (volatile species emitted fromplants that can partition into water), by •OH, SO4•–, and NO3•, and that of Tran et al.,98 who studiedoxidation by the aqueous phase SO4•– of a number of organic aerosol compounds including isoprene relatedcompounds, lactic and pyruvic acid.There have beenseveral studies on the oxidation of thin films by gaseous phase oxidants,e.g. refs −55,91−94•OH are on the order of 1010 M–1 s–1 and are comparable to other studies of aqueousphase •OH bimolecular constants.90 Relevant tothis study is the study by Witkowski and Gierczak88 who determined rate constants on the order 109 M–1 s–1 for reaction of aqueousphase •OH and cis-pinonic acid. Similar values ofbimolecular rate constants to those presented in •OH oxidation of substituted phenols.90 Arciva et al.90 determined second-orderrate constants on the order of 109–1010 M–1 s–1 for the reaction ofhighly substituted phenols with the aqueous phase •OH, and He et al.89 determined rate constantson the order of 109 M–1 s–1 for reaction of aqueous phase •OH with methoxyphenoliccompounds. Additionally, such reactions have been suggested as animportant source of aqueous secondary organic aerosol, SOA.102The second-order rate constantsdetermined in the current study for oxidation by aqueous phase 43 studied oxidation from the “bottomup” using OH radicals to oxidize a lipid, 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC), coating on a solid mixtureof NaCl and NaNO2 particles. The chemistry observed inthe work presented here, i.e., oxidation of a lipid from below inthe aqueous phase, supports their hypothesis that such reactions couldalso occur on aqueous droplets coated in an organic film.As discussed in the 25 suggesting that DSPC reacting with OH from thegaseous phase and the aqueous phase have similar chemical mechanisms.Further comparison of the kinetic profile observed in the currentstudy with those of real film material abstracted from the atmosphereto the aqueous-phase OH and nitrate radical44 also indicates a similar temporal profile. Thus, aqueous phase oxidationmay preferentially proceed via a multistep degradation mechanism asdescribed in the current work, but more studies on real atmosphericsamples are required to confirm this. Additionally, the mechanismmay be used to describe the aqueous phase radical induced oxidationof other saturated lipids, including those with different head groups.Theaqueous phase oxidation temporal profiles of DSPC shown here2–4 match•OH radical attack was estimated tobe ∼20 h using the following equation.•OH radicals given as 3.80× 10–16 mol dm–3.103 Typical atmospheric concentrations for NO3• and SO4•– are not readily available; therefore, the lifetime of DSPC withrespect to NO3• and SO4•– was not calculated.The lifetime of a monomolecularfilm of DSPC at the air–solution interface with respect toaqueous phase 3) may not need to be considered inatmospheric oxidation models suggesting that it should be readilyfound in atmospheric filter samples. The short atmospheric lifetime(<4–10 days3) calculated abovewould suggest that the oxidation chemistry described here is importantfor atmospheric oxidation modeling. The amount of DSPC measured inatmospheric filters may be less than that released to the environment,as the lifetime is short enough for DSPC to have been partially removedin the atmosphere before being captured on a filter. The lifetimecalculated in The lifetime ofDSPC is interesting because it provides a measure of the importanceof a lipid coating on atmospheric aerosol. A long-lived lipid (>4–10daysSupporting Information) and the relative amount of the film at the air–solutioninterface with time was estimated using the bimolecular rate constantslisted in •OH concentrations of 3.80 × 10–17 mol dm–3, 3.80 × 10–16 moldm–3,103 and 3.80 ×10–15 mol dm–3 to provide an envelopeof film lifetimes. These •OH concentrations bracketthe range of atmospheric •OH (aq) concentrationsdetermined in the literature,107 and the estimated film lifetime is sensitiveto these values. The estimated film lifetimes are shown in e of its initial value).The differential equationsused to describe the degradation mechanismwere solved analytically  indicates thatit takes ∼4–5 days for the amount of film material todecay to half of its initial amount, which is of the same order ofmagnitude as a typical aqueous aerosol lifetime and therefore suggeststhat oxidation initiated by the •OH radical maybe important to film lifetime in the atmosphere. The vertical dashedline emphasizes the film half-lives and indicates that the oxidationof the film depends on the •OH radical concentration.An •OH concentration of 3.80 × 10–15 mol dm–3 gives a half-life of ∼1/2 dayswhereas an •OH concentration of 3.80 × 10–17 mol dm–3 gives a half-life greaterthan 50 days which is atmospherically unimportant. Thus the atmosphericimportance of aqueous •OH oxidation is very sensitiveto •OH concentrations in particles in the atmosphere.Few studies of ambient •OH in droplets have beenconducted.103The solid black linein •OH, SO4•–, and NO3•. The decay was consistent with a multistep degradationmechanism with some products remaining at the air–solutioninterface that were subsequently oxidized by the aqueous radicals.Thus, lipid films on atmospheric aerosol will require several radicalreaction steps to remove all organic material from the interface andatmospheric aqueous phase oxidation of lipid films at the air–solutioninterface can be described by multistep kinetics.Theamount of deuterated material at the air–solution interfacewas observed to decay when a monolayer film of the fully deuteratedlipid DSPC was exposed to the aqueous phase radicals –16 mol dm–3 for aqueous hydroxylradicals.103 Oxidation of thin films inthe atmosphere by aqueous radicals may therefore be important, andreactions of lipid films appear consistent with a multistep degradationmechanism.An atmosphericlifetime of ∼20 h was calculated for a DSPCmolecule with respect to attack by an aqueous phase hydroxyl radicalusing a typical atmospheric concentration of aqueous hydroxyl radicals.The overall film lifetime was determined to have a half-life of ∼4–5days, calculated using the literature concentration of 3.80 ×10


Contactless bubble manipulation with a high spatiotemporal resolution brings a qualitative leap forward in a variety of applications. Despite considerable advances, light-induced bubble maneuvering remains challenging in terms of robust transportation, splitting and detachment. Here, a photopyroelectric slippery surface (PESS) with a sandwich structure is constructed to achieve the versatile bubble manipulation. Due to the generated dielectric wetting and nonuniform electric field under the irradiation of near infrared (NIR) light, a bubble is subject to both the Laplace force and dielectrophoresis force, enabling a high-efficiency bubble steering. We demonstrate that the splitting, merging and detachment of underwater bubbles can be achieved with high flexibility and precision, high velocity and agile direction maneuverability. We further extend the capability of bubble control to microrobots for cargo transportation, micropart assembly and transmission of gear structures. We envision this robust bubble manipulation strategy on the PESS would provide a valuable platform for various bubble-involved processes, ranging from microfluidic devices to soft robotics. Light-induced bubble maneuvering remains challenging in terms of response and functional adaptability due to the single driving mechanism including the Marangoni effect or asymmetrical deformation. Using a photopyroelectric slippery surface (PESS), Liu et al. demonstrate the splitting, merging, and detachment of underwater bubbles with high flexibility and precision. Various techniques leveraging structural and wettability gradients have been put forward to achieve bubble transportation by breaking the symmetric contact line to form a Laplace pressure gradient12. For instance, inspired by cactus spines and pitcher plants, slippery copper cones with geometry gradients were developed to achieve gas bubble transportation15. The operating capability mainly originates from the synergistic cooperation of the asymmetric morphology and slippery property of the surface, which help to generate a Laplace force to directionally move the gas bubbles and meanwhile endow a high affinity but low friction force to the bubbles13. However, the above techniques are limited by their functional adaptability, such as short-range bubble transport, fixed bubble moving trajectory, and non-real-time control.Gas bubbles are ubiquitous in natural environments, living organisms, and industrial production, and realizing flexible bubble manipulation in a liquid environment is critical for not only the basic understanding of various processes, ranging from gaseous microreactions to boiling transmission but also a variety of viable applications such as hydrogen production19, magnetism23, and light30 are introduced for bubble maneuvering. Among them, the light-driven bubble manipulation technique has been widely explored for its contactless and high spatiotemporal control. Specifically, non-directional bubble transportation can be achieved by either altering the gas-liquid interface tension or provoking a thermal capillary flow through photothermal effect in a real-time manner33, and these approaches for bubble control mainly resort to bubble asymmetrical deformation27, or Marangoni convection33, which always generates a weak driving force for small and slow bubble transportation. This further limits the versatility of efficient bubble detachment and splitting, thereby hindering their application in various practical settings.To circumvent these constraints, various external stimuli, including electricityIn this research, a photopyroelectric slippery surface (PESS) based on the photo-pyroelectric effect is developed to achieve multifunctional bubble manipulation. Due to the generated dielectric wetting and nonuniform electric field under the irradiation of near-infrared (NIR) light, a bubble is subject to both the Laplace force and dielectrophoresis force, enabling its transportation at a high velocity. We demonstrate that bubbles can move precisely along arbitrarily designed paths in an efficient manner with a wide volume range. More importantly, the PESS enables the splitting, merging, and detachment of underwater bubbles, which provides a promising avenue for selective chemical reaction, self-assembly, and cargo transportation.3O4 nanoparticles and polydimethylsiloxane (PDMS) was streamed on a commercial lithium niobate wafer acting as the pyroelectric layer, and the photothermal layer was obtained by curing the PDMS. Then a coating of hydrophobic SiO2 nanoparticles with a diameter of ~25 nm max of 27.4 °C s−1 and 22.9 °C s−1, respectively. The superior photothermal performance is attributed to the uniform dispersion of Fe3O4 nanoparticles in the PDMS. Moreover, the intensive and quick temperature variation in the range of 30 °C < T < 90 °C was achieved in more than seven cycles  of the lithium niobate crystal35. This further lowers the bound surface charges and gives rise to extra surface-free charges  versus bubble volume under different laser power indicates that V decreases with the increase of bubble volume and the decrease of laser power  and right (θB) contact angles are equal to the apparent contact angle (θ) as θ = θA = θB  that drives the bubble away from the light source. In combination with Eq.  can be approximately described by US = [2dγOL/ε0εd]0.5, where γOL is the oil/water surface tension41. Here, US is estimated to be 144.3 V under a saturation temperature change ΔT = 7.7 °C  in FDX is estimated to be of the order of 10–6 N, which is comparable to that of FL, indicating that the two forces contribute coherently to the bubble transport. In addition, as the bubble moves forward, a backward hydrodynamic resistance force FH comprising lubricant and liquid media’s viscous forces is generated, which could be expressed as44α is a numerical factor, μo and μl are the viscosity of oil and liquid, respectively. Therefore, the resultant force driving the bubble under NIR irradiation on the PESS is F = FL + FDX − FH /[R(μo + μl)]. Moreover, the bubble velocity increases with the laser power but decreases with the bubble volume . PDMS silicone elastomer was purchased from Dow Corning , which is used as the host matrix. Silicone oil (20 and 100 mPa s) and ethanol were purchased from Meryer Chemical Technology Co. Ltd. . Z-cut optical-grade lithium niobate wafers with a thickness of 0.5 mm were provided by Rayon Optical Materials . A commercial solution of superhydrophobic SiO2 nanoparticles was purchased from Rust-Oleum (USA). Quartz glass sheets were purchased from Beijing Zhong Cheng Quartz Glass Co. Ltd . Deionized water  was derived from a Mili-Q water purification system . The PESS is constructed with a sandwich structure, including a slippery layer, a pyroelectric layer, and a photothermal layer from top to bottom.Fe3O4 nanoparticles, PDMS prepolymer, and PDMS curing agent at a mass ratio of 0.6:1:0.1 were mechanically mixed for 10 min at 1000 rpm. Then the prepared mixture was placed in a vacuum chamber for 20 min to remove air bubbles, followed by spin-coated on the lithium niobate crystal wafers . The contact angle and sliding angle of the bubble on the surface were measured using an OCA25 Standard Contact Angle Goniometer . At least three measurements were performed on each surface. The temperature of the surface was monitored by a thermal infrared camera  and thermoelectric coupling thermometer .Supplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Movie 1Supplementary Movie 2Supplementary Movie 3Supplementary Movie 4Supplementary Movie 5Supplementary Movie 6Supplementary Movie 7Supplementary Movie 8Supplementary Movie 9Source Data


Further, glycerol-injected mice exhibited spinal deformity: significantly (p < 0.01) greater kyphotic angle than saline-injected mice. Glycerol-injected mice also demonstrated a significantly (p < 0.01) greater IVD degenerative score  at the upper-most lumbar level compared to saline-injected mice. These findings provide direct evidence that combined morphological (fibrosis) and functional (actively weaker and passively stiffer) alterations to the paraspinal muscles can lead to negative changes and deformity within the thoracolumbar spine.Degenerative spinal disorders, including kyphotic deformity, are associated with a range of degenerative characteristics of the paraspinal musculature. It has therefore been hypothesized that paraspinal muscular dysfunction is a causative factor for degenerative spinal deformity; however, experimental studies demonstrating causative relationships are lacking. Male and female mice received either glycerol or saline injections bilaterally along the length of the paraspinal muscles at four timepoints, each separated by 2 weeks. Immediately after sacrifice, micro-CT was performed to measure spinal deformity; paraspinal muscle biopsies were taken to measure active, passive and structural properties; and lumbar spines were fixed for analysis of intervertebral disc (IVD) degeneration. Glycerol-injected mice demonstrated clear signs of paraspinal muscle degeneration and dysfunction: significantly ( Degenerative spinal disorders are a multifactorial condition that are associated with a spectrum of indications related to skeletal muscle, including greater paraspinal fat5 and collagen content7, lower paraspinal muscle strength8, and altered paraspinal passive mechanical properties9. This isn’t surprising, as many chronic diseases are associated with skeletal muscle alterations13; degenerative spinal disorders are no exception. A broad literature has already linked myosteatosis (muscle fatty infiltration), fibrosis, and atrophy to numerous spine pathologies, including hyper-kyphotic deformity16, intervertebral disc (IVD) degeneration18, IVD herniation18, and nonspecific low back pain5. Further, patients with kyphotic deformity of the lumbar spine present with greater paraspinal muscle degeneration compared to patients without deformity6. These spinal deformity-related muscle alterations are important, as the sagittal imbalance associated with kyphotic deformity has been shown to be the most reliable radiographic predictor and indicator of the health status of adults with spinal disorders19. While paraspinal and spinopelvic muscular dysfunction are hypothesized to be causative factors in degenerative spinal deformity23, experimental studies demonstrating true cause and effect relationships are lacking.With a growing aged population, the number of patients being treated for degenerative spinal disorders is expected to increase24. Nonetheless, whether muscle alterations are consequences of spine degeneration and deformity or whether they precede, drive, or accompany the disorder progression is unknown; causative data are needed to address such hypotheses. However, because of the long progressive time‐course of degenerative spine disorders in humans, and the lack of muscle data at asymptomatic early disease stages, it is unrealistic to obtain such data in humans. Few animal studies have attempted to untangle the relationship between paraspinal muscle pathophysiology and degenerative spinal deformities26. Cho et al.25 found that severe paraspinal muscle injury (2-week ischemia) in rats led to a thoracolumbar kyphotic deformity; however, the authors did not quantify the degenerative changes in the muscles and the mechanism of muscle injury was likely non-physiologic. Similarly, Hey et al.26 used a whole body TSC1 knockout myopathy model in mice, and demonstrated that whole body muscle myopathy leads to thoracolumbar kyphotic deformity in 12-month old mice when compared to age-matched controls. However, this study was limited in that the myopathy was not specific to the paraspinal muscles, but rather affected the entire skeletal muscle system, and the quantity of muscle fibrosis and fatty infiltration were not measured, nor were any functional measures performed.Recent work demonstrated large variability in the active (specific force) and passive (elastic modulus) functional properties of paraspinal muscle biopsies from degenerative adult spinal deformity patients, reporting values that appear to be impaired compared to age-matched literature skeletal muscle norms29. Further study of the interrelationships that drive the initiation and progression of spinal degeneration, including paraspinal muscle and IVD degeneration and kyphotic deformity, is needed.Also of interest, is whether the active process of paraspinal muscle degeneration can initiate other spinal degenerative changes such as IVD degeneration. The opposite relationship, where the initiation of IVD degeneration leads to degenerative changes to the paraspinal muscles, has been demonstrated in multiple animal modelsTo better unravel the cause-and-effect association between paraspinal muscle degeneration and spine degeneration and deformity, we developed and characterized a novel model of paraspinal muscle degeneration using repeated experimental intramuscular glycerol injections in C57BL/6 wild type mice. It was hypothesized that the induced paraspinal muscle degeneration would lead directly to kyphotic spinal deformity and mild degeneration of the IVDs.p < 0.01; ES: glycerol = 15.1% vs saline = 4.5%; main effect of group = p < 0.0001) , where the difference between glycerol and saline groups was greater in females than males. There was no main effect of sex (p = 0.056). In the ES muscle there was no interaction (p = 0.58) or sex effect (p = 0.22). Unexpectedly, glycerol injected mice did not demonstrate a significant difference in fat deposition compared to saline injected mice in either muscle   or interaction effects . Qualitatively, a greater number of central nuclei, more inhomogeneous fibre size distribution, and an infiltration of mononucleated inflammatory cells were found in the glycerol compared to saline groups  compared to saline injected mice for both muscles  Figs. a. There ct p = 0.2. Unexpe2 vs Saline = 61.3 mm2, p = 0.41)  but no interaction (p = 0.98). For dorsal muscle density, a main effect of group was present  but no effect of sex  and no interaction (p = 0.41)  at the L3 level between glycerol and saline treated mice  and no interaction,  but a main effect of sex for the MULT   and the MULT in female but not male mice . In the ES there was no sex (p = 0.14) or interaction effect (pp = 0.63), and in the MULT there was a main effect of sex (p < 0.01)  nor was there an effect of sex  or an interaction (MULT: p = 0.83 ES: p = 0.10)  nor was there an effect of sex (p = 0.74) or an interaction (p = 0.52) in the MULT; however, in the ES there was a significant effect of group (p = 0.01), where the glycerol group had a lower active modulus  compared to the saline group, but no effect of sex (p = 0.587) and no interaction (p = 0.11)  and no interaction effect (MULT: p = 0.11 ES: p = 0.66) in either muscle. However, there was a main effect of sex in the MULT (p = 0.02) with males having a 34% faster rate of force development than females. There were no sex differences in the ES (p = 0.36)  Fig. .Figure 5p < 0.01), with an 80% greater passive elastic modulus in the ES from the glycerol compared to saline injected groups. There was no effect of sex (p = 0.52) and no interaction effect (p = 0.44)  Fig. .Figure 6p < 0.01). There was no effect of sex (p = 0.052) and no interaction effect (p = 0.65)  with no effect of sex (p = 0.5915) and no interaction effect (p = 0.5758)  compared to saline injected mice  Fig. a, b. Lumt p = 0.558 . There was no significant effect of sex and no interaction effect for any level .There was no significant group difference in the degenerative score between glycerol and saline injected mice with the exception of the L1/2 vertebral level Fig. : , followed by the annulus fibrosus  and finally the nucleus/annulus boundary .23. However, direct evidence in support of this hypothesis is incomplete. Here, employing a mouse model of repeated intramuscular glycerol injections over an 8-week period, it is shown that the paraspinal muscles of glycerol injected mice have significantly more fibrotic tissue, greater number of central nuclei (inferring that the muscle is undergoing cycles of degeneration and regeneration), produce less absolute active force, and are passively stiffer. Further, a direct link is established between these unfavourable muscle properties and the development of thoracolumbar hyper-kyphotic deformity. The main findings of this study are that (1) paraspinal degeneration can lead directly to hyper-kyphotic deformity; the kyphotic Cobb’s angle was significantly (68%) greater in the glycerol compared to the saline injected mice at the final timepoint (day 56); (2) paraspinal muscle weakness  and passive stiffness  appear to be the dominant muscle functional parameters leading to the hyper-kyphotic deformity in this model; (3) the hyper-kyphotic deformity is not accompanied by significant IVD degeneration, but there are signs of mild IVD degeneration developing at the upper-most lumbar level. These findings provide direct evidence that both morphological (fibrosis) and functional (actively weaker and passively stiffer) alterations to the paraspinal muscle compartment can drive negative changes to the thoracolumbar spine—evidence that has been lacking in the literature to date.The pathophysiology driving degenerative spinal disorders and spinal deformity is complex and has been suggested to involve the paraspinal muscles25). Previous studies have proposed that kyphotic deformity develops because of postural changes—as a method of conserving energy26, while others have suggested that intervertebral disc degeneration, which can lead to a loss of disc height and bone remodelling, could contribute to the onset of deformity31. Finally, many have hypothesized that paraspinal and spinopelvic muscular dysfunction are causative factors in the development of spinal deformity23. While presenting compelling hypotheses, these studies are unable to unravel the sequence of events that lead to kyphotic deformity. This gap in the literature is significant as the sagittal imbalance that arises alongside kyphotic deformity has been shown to be the most reliable radiographic predictor and indicator of the health status of adults with spinal disorders19.Limited studies have attempted to demonstrate that paraspinal muscle pathophysiology can precede, and directly lead to, negative changes to the spine , and fibrosis (tissue remodeling whereby muscle tissue is replaced by collagen-based connective tissue). For example, fatty and/or fibrotic changes have been regularly observed using non-invasive imaging in IVD herniation37, kyphotic deformity6, combined kyphotic and scoliotic deformity24, and IVD herniation7 patients. However, the current glycerol model did not induce a significant amount of fatty infiltration as quantified by ORO staining, which is largely in contrast to previous studies using single glycerol injections into mouse limb muscles38 and reporting on human LBPD patients where fatty infiltration is generally prominent within the paraspinal muscles using non-invasive imaging .The intramuscular glycerol injection model employed here induced a significant amount of fibrosis, and a subsequent increase in passive muscle stiffness in the paraspinal muscles, which mimics the findings of histological studies demonstrating greater amounts of fibrotic tissue in chronic lumbar spine pathology25 found that severe paraspinal muscle injury (2-week ischemia) in rats led to a thoracolumbar kyphotic deformity that persisted for the remainder of the study (12 weeks); however, the authors did not quantify the degenerative changes in the muscles. A recent study knocked-out the TSC1 gene in female mice to create a myopathy within the entire skeletal muscle system and revealed that whole body muscle myopathy leads to thoracolumbar kyphotic deformity in 12-month, but not 9-month-old mice when compared to age-matched controls26. This study26 was limited in that the myopathy was not specific to the paraspinal muscles, but rather affected the entire skeletal muscle system, and the quantity of fibrosis and fatty infiltration were not measured, nor were any functional measures performed. Other mouse models with known whole body skeletal muscle weakness (e.g. Mdx mice39 and tetranectin-deficient mice40) have also been shown to develop spinal hyper-kyphosis.While there is a growing body of human literature demonstrating links between altered paraspinal muscle morphology and LBPDs, much is still unknown regarding their direct mechanistic interaction. Specific to deformity, Cho et al.41 reported that a smaller cross-sectional area and lower quality of thoracic paraspinal muscles were associated with a larger kyphotic Cobb angle in a population aged 50 years and above. In the current study, micro-CT analysis provided broader measures of dorsal muscle CSA  and density  at the L3 vertebral level. While glycerol injections did not alter the overall dorsal muscle CSA, dorsal muscle density was significantly lower in glycerol injected compared to saline injected mice. This lower density is reflective of a lower percentage of the muscle occupied by contractile tissue which again demonstrates a direct link to the development of spinal deformity.Recent work by Lorbergs et al.42; however, this is the first study to show the inverse relationship, whereby changes to passive muscle properties likely precede pathological changes to the spine. Future studies should investigate multiple timepoints using in-vivo imaging and/or the addition of more animals to improve precision over the exact timing of events driving changes to the paraspinal muscles and the development of spinal deformity.To our knowledge this is the first study to investigate whether impaired paraspinal muscle function can precede and thus lead to spinal deformity. Here, lower absolute force production was apparent in the ES (both sexes) and MULT  in the glycerol injected compared to saline injected group. As neither fibre CSA nor specific force were statistically different between glycerol and saline groups, it is likely the combination of small differences in both (i.e. slightly lower CSA and specific force in the glycerol group) that leads to the larger and statistically significant differences in absolute force. This is partially supported in the ES by the significant difference in active modulus (25% lower in the glycerol group), suggesting that even when accounting for the size of the fibre, there were fewer attached cross bridges during active steady-state isometric force production. This implies that ES specific force may have been trending towards being significantly lower in the glycerol group. Most notably, a clear and significant difference was observed in the passive elastic modulus between groups for the ES , likely a result of the significantly greater amount of collagen in the muscle. The sensitivity to passive muscle remodelling is not surprising, as previous studies have also revealed changes to the passive mechanical properties of the spine muscles in response to spine pathologyThe results of the IVD analyses demonstrate, at most, the presence of mild degeneration . Statistically significant differences between glycerol and saline groups were present only at the L1/2 level . While this L1/2 score of 1.1 (out of 10) in the glycerol group represents very mild degeneration, L1/2 was the most cranial level analyzed, thus representing the level closest to the onset of the deformity. As such, the small difference between the glycerol and saline groups at this (L1/2) vertebral level may be indicative of accelerated degeneration in the glycerol group that would have progressed further over a longer time period and/or the presence of progressing degeneration in IVDs located more cranially in the region of deformity. Despite this possibility, it is clear that the development of deformity has preceded any meaningful IVD degeneration in the lumbar region.Two muscle measures demonstrated a stronger effect in female compared to male mice. The first, collagen content as quantified by histology, was greater in the glycerol injected muscles of both males and females, but the effect was significantly larger in the MULT of females compared to males. The second, absolute force, was significantly lower in both sexes of the ES in glycerol compared to saline muscles, but in MULT was only lower in the glycerol compared to saline muscles of females and not males. Despite these stronger degenerative phenotypes in the female compared to male muscles, there was no sex-based difference in the magnitude of kyphotic deformity induced by glycerol injections.It should be noted that while the current results demonstrate a clear link between paraspinal muscle myopathy and spinal deformity, this should not be directly extrapolated to humans, who have clear functional differences when compared to rodents (e.g. biped vs quadruped), and whose lumbar spine is lordotic (humans) while rodents have a much flatter lumbar region.In summary, this study has successfully demonstrated that: (1) experimental intramuscular glycerol injections in C57BL/6 wild type mice lead to muscle degeneration including severe muscle fibrosis, passive muscle stiffening and impaired absolute force production. Interestingly, multiple glycerol injections in mice did not lead to a significant increase in fatty infiltration within the paraspinal muscles. (2) Paraspinal muscle myopathy leads directly to kyphotic spinal deformity; thus, providing the first direct evidence that paraspinal degeneration can initiate the development of spine deformity.38 and has been shown to induce early fibrosis in the rat.43 Here injections were performed every 14 days for 42 days (4 injection timepoints) with the aim of creating a degenerative environment within the paraspinal muscle compartment.Experiments were performed on 10–12-week-old female (n = 12) and male (n = 12) C57BL/6 mice (Charles River Laboratories) approved by the University of Guelph Animal Utilization Protocol (#4533) in accordance with all relevant guidelines and regulations; reporting of methods here follow ARRIVE guidelines. All mice were 22–26 g at the start of the experiment and allowed free cage activity and ad libitum access to food and water. Mice were housed in standard 22 °C conditions. Twelve mice  received bilateral glycerol injections to the mid-belly of the multifidus and erector spinae muscles along the ~ L1–L6 vertebral levels to induce muscle myopathy. Twelve control mice  were injected identically, but with saline instead of glycerol. Glycerol provokes muscle regeneration by inducing myofibre necrosis and intramuscular fat deposition in mice2 asphyxiation.Mice were continuously anaesthetized with 2% inhaled isoflurane at 2 L/min and injected subcutaneously over the incision site with a 50/50 lidocaine-marcaine mixture. The depth of anaesthesia was assessed by toe pinch. The dorsal side of the mouse was shaved and sterilized with betadine. A 2–3 cm incision was made through the skin over the lumbar spine exposing the multifidus and erector spinae muscles. 15 μl of either glycerol (50% v/v) or sterile saline was then injected bilaterally in each of the lumbar multifidus and erector spinae, from L1 to L6, with a 29.5-gauge insulin syringe. Skin incisions were closed with EZ Clips. Mice were allowed free cage activity and were monitored daily for signs of pain, distress, and infection. Intramuscular injections were performed every 14 days for 42 days ; mice were sacrificed 14 days following the final injection under anaesthesia followed by CO2) and density [in Hounsfield units (HU)], the multifidus, erector spinae, and quadratus lumborum were combined and will be referred to as ‘dorsal muscle’; muscles were combined because they couldn’t be separated reliably, similar to previous publications in the field.44 First, a grey value threshold (33–90) was applied to exclude non‐lean tissue (i.e. mostly bone), then a region of interest was manually drawn on the dorsal muscle area at L3  was normalized to body mass, and dorsal muscle density was normalized to spleen density . The muscle‐to‐spleen ratio is referred to here as muscle density44.Micro‐CT imaging was performed immediately following sacrifice to measure paraspinal muscle cross-sectional area (CSA), muscle density, and spinal deformity. Scanning was performed with a Skyscan 1278  at 50 μm voxel resolution using a source voltage of 48 kV and a current of 1030 μA. Aluminium filter was set at 0.5 mm to optimize contrast while minimizing dose. Rotation step for the X‐ray source was set to 0.7°. Average scanning time per animal was 2.5 min. Raw images were then reconstructed with NRecon to 3D cross‐sectional image data sets using the following parameters: beam hardening to 20%, smoothing to 2%, minimum and maximum for CS to Image Conversion to 0% and 0.03%, respectively. Analyses of muscle CSA and density from reconstructed images were performed using SkyScan software (CTan). To measure CSA  and lordosis (superior endplate of S1 to the superior endplate of L1) angles with Surgimap software (version 2.3.2.1) Fig. d.Biopsies of multifidus and erector spinae from saline and glycerol injected mice were harvested immediately after the Micro-CT and split into two pieces each. The first were immediately placed into a cold dissection solution for contractile and mechanical testing (described later). The second pieces were embedded in OCT compound (Tissue-Tek), frozen in liquid nitrogen-cooled isopentane, stored at − 80 °C, and cut into 10-μm-thick cryosections with a cryostat (Leica CM1850) maintained at − 20 °C. Histological staining included hematoxylin and eosin (H&E), picrosirius red + fast green (PR + FG), and oil red O (ORO); PR + FG and ORO were used to detect collagen and fat, respectively. One to two images per muscle per stain were acquired with a brightfield Leica DM 5000B microscope connected to a Hamamatsu Orca-Flash 4.0 digital camera and Velocity imaging software. PR + FG and ORO images were thresholded in ImageJ and the red-positive area  was divided by the total area to provide a measure of collagen and fat area fractions.45 On the day of a contractile or passive mechanical experiment, fibre bundles were removed from storage solution and placed in relaxing solution on ice.The muscle pieces from the cold dissection solution were further dissected into fibre bundles 3–5 mm in length and ~ 0.5 mm in diameter. Following dissection, bundles were immersed for 30 min in skinning solution with 0.5% non-ionic detergent Brij 58 and then placed in storage solution and maintained for 24 h at 4 °C, followed by storage at − 80 °C.2·6H2O, and 2 ATP, and dissolved in glycerol so that the final volume of glycerol was 50% v/v. The skinning solution was identical to the storage solution except glycerol was replaced by deionized water and 0.5% w/v Brij 58 was added. Relaxing solution consisted of (in mM) 59.4 imidazole, 86 KMSA, 0.13 Ca(MSA)2, 10.8 Mg(MSA)2, 5.5 K3 EGTA, 1 KH2PO4, 0.05 leupeptin, and 5.1 Na2ATP. The pre-activating solution consisted of KPr (185), MOPS (20), Mg(CH3COOH)2 (2.5), ATP (2.5) while the activating solution contained Ca2+ (15.11), Mg (6.93), EGTA (15), MOPS (80), ATP (5), CP (15), K (43.27), Na (13.09), H2O. All solutions were adjusted to a pH of 7.0 with the appropriate acid (HCl) or base (Tris).The storage solution was composed of (in mM) 250 K-propionate, 40 Imidazole, 10 EGTA, 4 MgClo) was measured by aligning the innermost portion of the nylon tie at each end of the fibre with the crosshairs of a microscope eyepiece graticule. Measurements of fibre diameter were taken at 3 locations along the fibre length using a micromanipulator; from these measurements fibre CSA was calculated .Briefly, single fibres were carefully removed from bundles and transferred to an experimental chamber containing relaxing solution maintained at 15 °C. There, fibres were tied with one end secured via monofilament nylon sutures to a pin in series with a force transducer  and the other end secured in a similar manner, to the lever arm of a servomotor . The length of the fibre was adjusted to obtain the target sarcomere length using a high-speed camera . Fibre length (L2+ activating solution (pCa 4.2) to elicit maximal force. Force and length data were sampled at a rate of 10,000 Hz. Maximal force was calculated as the peak amplitude (peak force achieved in activating solution minus the resting force in relaxing solution), which was then divided by the CSA of the muscle fibre to give a measure of specific force (Sfo). Once maximal force was developed, active modulus  was assessed by inducing a rapid (500 Lo/s) stretch of 0.3% of Lo and dividing the change in force  during the stretch by the length change .Relaxed single fibres were set slightly beyond their expected optimal length  and activated by first immersing them in a chamber containing a pre-activating solution for 30 s and then moving them to a chamber containing a high-Carate of force redevelopment (ktr). This was done by rapidly shortening the fibre by 15% of Lo at a rate of 10 Lo/s followed by a rapid (500 Lo/s) re-stretch back to Lo. The rapid shortening causes all cross-bridges to break, and then the re-stretch allows further dissociation of any remaining cross-bridges and redevelopment of force independent of Ca2+-dependent regulatory proteins at Lo. A mono- exponential equation, y = a (1 − e−kt) + b, was fit to the redevelopment curve to determine ktr47. After completion of the contractile testing, fibres were placed in 15 μl of solubilization buffer and stored at − 80 °C for a minimum of 48 h. The myosin heavy chain (MHC) composition of each fibre (i.e. fibre type) was determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE)48.Again, at maximal force, an additional length step was induced to measure 49. Force and sarcomere length were recorded as bundles were rapidly stretched (at a rate of two bundle lengths per second) by cumulative increments of ~ 0.25 µm/sarcomere. For example, if slack sarcomere length was 2.1 µm, the first stretch would reach a mean sarcomere length of approximately 2.35 µm, the second stretch would occur from a mean sarcomere length of approximately 2.35–2.60 µm, and so on; for each test, 5–7 stretches were required for the test to be successful. After each stretch, sarcomere length was measured and the bundle was allowed to relax for 2 min before force was recorded and the next stretch was performed. This force was normalized to the CSA calculated from the average of the diameter measures  to give a value of stress. For each bundle a, passive stress-sarcomere length curve was generated, and the slope of the linear portion of this curve (beyond approximately 3.4 µm) was calculated to determine the passive elastic modulus.For passive measurements, testing was performed in relaxing solution. Two to three muscle fibre bundles (8–20 single fibres ensheathed in their extracellular matrix) were dissected and tested from each erector spinae muscle sample. Bundles were then tied at either end to two separate pins: one attached to a force transducer , the other to a lever arm of a servomotor . Bundles were set to their slack length (length at which passive resistance to stretch was first detected) and measurements of diameter were taken at three locations along the bundle length using a digital micromanipulator (precision 1 µm) while viewed under a stereo microscope. Bundles were transilluminated at their approximate mid-length by a 5-mW diode laser  and the resultant diffraction pattern was used to calculate sarcomere length50, where the nucleus pulposus, annulus fibrosus, and the nucleus/annulus boundary were graded from 0 to 4, 0 to 4, and 0 to 2, respectively, and the total scores summed (for minimum and maximum scores of 0 and 10). Data are presented as the scores averaged from both evaluators.Lumbar spines  were harvested from both saline and glycerol injected C57BL/6 mice. Spines were fixed and decalcified for 3 days in Cal-Ex™ II (Fisher Scientific™). After decalcification, the spines were transferred to a cassette and placed into a 70% ethanol solution before being dehydrated in isopropanol, cleared in xylene, and infiltrated with paraffin. Sagittal plane sections (5 µm) were made through the approximate spine midline and stained using Safranin-O Fast Green. Sections were cover slipped and imaged at 20X on a brightfield Leica DM 5000B microscope connected to a Hamamatsu Orca-Flash 4.0 digital camera and Velocity imaging software, followed by scoring by two blinded evaluators using a modified scoring criteriaAll data were analysed by two-way analysis of variance (ANOVA), with factors of group  and sex . If a significant interaction was discovered, Sidak multiple comparisons were used to compare individual group differences between males and females within the two-way ANOVA. Significance was set to α = 0.05. All data are reported as means ± 95% CI.


In the published article, there was no Funding statement. The correct Funding statement appears below.FUNDINGThe study was funded by the Italian Ministry of Health through Institutional “Ricerca Corrente” (LB and MT) L2/3 project to LB “Tumor antigen discovery for innovative cancer immunotherapies in HCC: from benchside to bedside (HepAnt)”. L2/13 project to MT “Peptide optimization to improve antigen presentation and anti-tumor response for sarcomas”.The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.


This study provides a novel method of synthesizing high-lignin-content carbon cryogels with promising potential for application in the field of energy storage devices.A cost-effective and sustainable method is successfully developed to produce lignin-based cryogels with a mechanically robust 3D interconnected structure. A choline chloride–lactic acid (ChCl–LA)-based deep eutectic solvent (DES) is used as a cosolvent to promote the synthesis of lignin–resorcinol–formaldehyde (LRF) gels that can self-assemble a robust string-bead-like framework. The molar ratio of LA to ChCl in DES has a significant influence on the gelation time and properties of the ensuing gels. Moreover, it is discovered that doping the metal–organic framework (MOF) during the sol–gel process can greatly accelerate the gelation of lignin. It takes a mere 4 h to complete the LRF gelation process at a DES ratio of 1:5 combined with 5% MOF. This study yields LRF carbon cryogels doped with copper that exhibit 3D interconnected bead-like carbon spheres with a prominent micropore of 1.2 nm. A specific capacitance as high as 185 F g Carbon aerogels (CAs), as a novel and unique porous carbon material with an interconnected structure, have abundant micropores and mesopores, a high specific surface area, controllable porosity and permeability, and higher electrical conductivity . They seIn fact, lignin enriched with highly reactive phenolic hydroxyl groups can replace resorcinol with formaldehyde to form lignin–resorcinol–formaldehyde (LRF) gels via the sol–gel method ; however2+ oxidation of resorcinol in the solution during the cure cycle , C18H6Cu3O12, Mw 606) was synthesized by the solvothermal method [The LNP sample  with formaldehyde (37 wt.% in water) in DES (4 mL) as well as HKUST–1 added as a catalyst, according to the recipes in 2 flow (200 mL min−1), heated from room temperature to 800 °C at a heating rate of 5 °C min−1, and kept for 2 h, to produce the resultant LRF carbon cryogels. The flow chart of the LRF carbon cryogels’ preparation is shown in The dried LRF cryogels were pyrolyzed on a tube furnace under NMorphology and composition of the samples were characterized using SEM  coupled with energy dispersive spectroscopy (EDS). All the specimens were gold-sputtered and tested at an accelerating voltage of 15 kV.Microstructure of the LRF carbon cryogel was characterized using TEM .−1 with a resolution of 4 cm−1. Each specimen was tested twice.FTIR tests were performed on a Vertex 70 spectrophotometer  equipped with an attenuated total reflectance (ATR) cell. The wavenumber region ranged from 4000 to 400 cmα radiation at a 2θ angle range of 2–40°, with a scanning step of 0.01° and a scanning rate of 2° min−1.XRD patterns were recorded on a D8 Advance diffractometer  using Cu K−1 under N2 atmosphere.TGA was tested on a TGA–55 instrument . Each sample ran from 30 to 800 °C at a heating rate of 10 °C min2 adsorption–desorption isotherms were determined using an ASAP 2460 automated gas sorption analyzer . The specific surface area (SSA) was calculated by the Brunauer–Emmett–Teller (BET) method, the pore size distribution (PSD) by the Barret–Joyner–Halenda (BJH) model, and the micropore distribution by the t-plot method.N−1, the galvanostatic charge–discharge (GCD) curves were obtained at current density of 0.5 to 5 A g−1, and the electrochemical impedance spectroscopy (EIS) worked at an open-circuit voltage in a frequency range of 10−2–105 Hz. The specific capacitance was calculated by Equation (1) [C is the gravimetric specific capacitance (F g−1), dI is the discharge current (A), ∆t the discharge time (s), ∆U the potential interval (V), and m the mass of active material on the electrode (g).Electrochemical measurements were carried out on a CHI660E electrochemical workstation  at room temperature with 6 M KOH electrolyte in a typical three-electrode cell with Ag/AgCl as reference electrode and platinum wire as counter electrode. The working electrode was produced with nickel foam pasted with the homogeneous mixture of the LRF carbon cryogel with acetylene black and the binder , with a mass ratio of 8:1:1. The cyclic voltammetry (CV) tests were performed within a potential window of −1 to 0 V at a scan rate range from 5 to 50 mV stion (1) .(1)C=Id+ ions, providing a proper proton acid catalyst and structure-directing agent (SDA) for fast gelation of the LRF [Given the previous success, the optimized 75% lignin-to-resorcinol replacement was used for the preparation of the LRF cryogels [ the LRF ,25.SEM images of the LRF cryogels showed that LNP with formaldehyde could self-assemble into a highly robust 3D interconnected framework in the DES cosolvent. As the molar ratio of LA in the DES increased from 1:2 to 1:10, the individual nanosphere size in the LRF framework became smaller. Obviously, at a DES ratio of 1:5, the small nanoparticles of the LRF gel would be liable to agglomerate and form larger clusters with a self-assembled 3D interconnected framework by intermolecular van der Waals forces and hydrogen bonds in the DES system . By furtAs mentioned earlier, HKUST–1 has been shown to improve the porosity of gel-derived carbon, which could also introduce new electro-functionality to the gels . Thus, w2+) and BTC anions to form a neutral net structure where the paddle-wheel secondary building unit has four carboxylate groups in four BTC ligands that link together with two copper ions [2+ and to a chelating reaction with chloride ions in the DES system. Benefitting from the introduction of Cu2+ from HKUST–1 hydration, the presence of methoxy, phenolic hydroxyl, and carboxyl groups in LNP structure allowed Cu2+ to be coordinated, thus Cu2+ acted as metal cation catalyst in the sol–gel process to facilitate the condensation and polymerization of lignin with formaldehyde [In the previous study, it was observed that 2,4–dihydroxy–benzoic acid (DHBA) combined with copper nitrate used in an alkali solvent during the sol–gel process effectively incorporated metal species into organic aerogels, whereas when only copper nitrate was added into a sol–gel solution it was unable to form phenolic gels . More imper ions . It is paldehyde . TherefoUnder the desired DES ratio of 1:5, the control tests with MOF doped as a catalyst demonstrated that the nanosphere size of primary particles in the LRF gels’ framework gradually decreased with an increase in MOF load. Moreover, the nanoparticle size and branch chains of the LRF gels’ interconnected framework depended on the copper content in the matrix. With an amount of MOF of 10%, the produced branch chains were longer and nanoparticle clusters became larger . This su5 substitution of lignin aromatic nucleus from guaiacyl (G) and p–hydroxylphenyl (H) subunits or with the lignin propenyl side chains [−1 can provide the pivotal structural information on the C–O stretch bond on the side chain and for C=C on aromatic rings. The peak around 1735 cm−1 in LNP, attributed to C=O stretching of unconjugated ketones and carbonyl groups, was more visible in the spectra of the LRF gels. This observation suggests that aldehydes, which initially presented in lignin, might have contributed to its crosslinking and/or reacted with resorcinol in the gelation reaction to a large extent [−1 disappeared . The SSA was 33.78 m2 g−1 for the BET model, much higher than that of other LRF cryogels .The thermal stability of the synthesized LRF cryogels was determined. As illustrated in sis loop , suggest2 adsorption–desorption isotherms of the LRF carbon cryogels at 196 °C. They belonged to type I of the IUPAC classification [0 < 0.1). The N2 uptake obviously increased at a higher relative pressure (P/P0 > 0.9) after micropore filling. In the condensation process, the curved surface changes with the increase in P/P0 in capillary pores was reversible; there was a change in the curved surface formed by the evaporation process when P/P0 decreased, resulting in the adsorption/desorption isotherms overlapping without a hysteresis circle [The resultant LRF carbon cryogels were obtained at 800 °C through slow pyrolysis. The highest solid yield of 38.8% was obtained from the LRF cryogel of DES1:5+5%MOF, which represented the highest stability framework structure among these LRF cryogels. In contrast to the initial LRF cryogel, the SSA and porosity of the ensuing LRF carbon cryogels were significantly improved. fication , typicals circle . Figure 2 g−1 by BET theory, along with the MOF load increasing in the LRF cryogel precursors (3 g−1) as well as a micropore area of 408 m2 g−1 and a micropore volume of 0.21 cm3 g−1 calculated by the t–Plot method, which suggests that HKUST–1, as a superb catalyst, had a significant influence on the microstructure of the LRF carbon cryogels, consistent with the results of doping metal salts  into phenolic mixtures, which can improve the porous structure of carbon aerogels [It has been reported that the carbonous material with a hierarchical porous structure was an ideal electrode for improving the supercapacitor performance, suggesting the that the micropores (<2 nm) can accommodate charge and strengthen capacitance, the mesopores (2–50 nm) favored ion transport, and the macropores (>50 nm) help to allow ion buffering . Furtherecursors . For exaaerogels ,33. It cθ position of 26.5 ° and 43.2 °  as well as fast electron transport for pseudocapacitance behaviors, which can be attributed to the doped copper and oxygen in carbon cryogels. In addition, the GCD curves of all samples at 0.5 A g−1 showed a quasi-symmetric isosceles triangle , charge transfer resistance (Rct), Warburg impedance (W), and double-layer capacitance (Cd) [s = 0.5 Ω for the LRF carbon cryogel of DES1:5+5%MOF suggested that this electrode had the highest charge transfer efficiency and highest conductivity on the electrode–electrolyte interface. Moreover, all Rct of the high-frequency curves with a faint semicircle revealed that the ion transfer in the electrolyte offered a small resistance and fast ion transport in the electrode, owing to the crosslinked hierarchical porous structure as well as a proper graphitization [The Nyquist plot of the frequency range displayed a semicircle in the high-frequency range and a straight line in the low-frequency range as shown in nce (Cd) . In the tization . Electrotization .−1 both LRF carbon cryogels of DES1:5+5%MOF and DES1:5+10%MOF achieved 185 F g−1 and 180 F g−1, respectively, while the DES1:5 sample without MOF gained the lowest specific capacitance of 135 F g−1. As the current density increased to 5 A g−1, the DES1:5+5%MOF sample could still maintain 142 F g−1, revealing that it had the highest capacitance retention rate and stability. Compared to other supercapacitor electrodes of carbon materials prepared by electrospinning, chemical activation, etc., the LRF carbon cryogels exhibited the highest specific capacitance  and commercial multi-wall carbon nanotubes  [−1), BC–LRF carbon aerogels, lignin/TOCNF–derived carbon aerogels (LTCA), and alkali lignin carbon (ALC) [The specific capacitances of three LRF carbon cryogels were calculated based on the GCD curves . The intacitance e. Lignin9 F g−1) . Compares MWCNT,  F g−1 [−on (ALC) ,41.−1  can catalyze the gelation kinetics of LRF formation and further improve the hierarchical pores’ microstructure. Therefore, by combining a 5% MOF load with a DES ratio of 1:5 can significantly prompt the formation of LRF gels as well as greatly shorten the gelation time to as fast as 4 h. The subsequent LRF carbon cryogels have shown a promising potential for application in high-performance electrochemical capacitive energy storage, exhibiting excellent performance with the specific capacitance of 185 F g


In malignant cerebral infarction decompressive hemicraniectomy has demonstrated beneficial effects, but the optimum size of hemicraniectomy is still a matter of debate. Some surgeons prefer a large-sized hemicraniectomy with a diameter of more than 14 cm (HC > 14). We investigated whether this approach is associated with reduced mortality and an improved long-term functional outcome compared to a standard hemicraniectomy with a diameter of less than 14 cm (HC ≤ 14).Patients from the DESTINY  registry who received hemicraniectomy were dichotomized according to the hemicraniectomy diameter (HC ≤ 14 cm vs. HC > 14 cm). The primary outcome was modified Rankin scale (mRS) score ≤ 4 after 12 months. Secondary outcomes were in-hospital mortality, mRS ≤ 3 and mortality after 12 months, and the rate of hemicraniectomy-related complications. The diameter of the hemicraniectomy was examined as an independent predictor of functional outcome in multivariable analyses.Among 130 patients  age 55 (11) years), the mean hemicraniectomy diameter was 13.6 cm. 42 patients (32.3%) had HC > 14. There were no significant differences in the primary outcome and mortality by size of hemicraniectomy. Rate of complications did not differ . Age and infarct volume but not hemicraniectomy diameter were associated with outcome in multivariable analyses.In this post-hoc analysis, large hemicraniectomy was not associated with an improved outcome or lower mortality in unselected patients with malignant middle cerebral artery infarction. Randomized trials should further examine whether individual patients could benefit from a large-sized hemicraniectomy.https://www.drks.de; Unique Identifier: DRKS00000624).German Clinical Trials Register (URL: The online version contains supplementary material available at 10.1007/s00415-023-11766-3. In malignant cerebral infarction space-occupying brain edema is associated with a mortality of up to 80% despite intensive care treatment . Early hThe volume gained by hemicraniectomy directly correlates with the diameter of the bone flap. Current recommendations are based on in vitro models which calculated a minimum diameter of 12 cm to create an additional volume of at least 80 ml . While hBetween January 2010 and July 2016 patients with large ischemic infarction were prospectively included into the DEcompressive Surgery for the Treatment of malignant INfarction of the middle cerebral arterY—Registry (DESTINY-R) study in 30 neurological and neurosurgical departments in Germany and Austria.A detailed description of the study design has been published previously . The triFor this analysis patients who fulfilled the following inclusion criteria were selected from the complete study cohort: (1) ischemic infarction of at least 50% of the middle cerebral artery territory confirmed by computed tomography (CT) or magnetic resonance imaging (MRI) with corresponding clinical signs of a severe hemispheric syndrome, with or without additional infarction of the ipsilateral anterior or posterior cerebral artery territory, (2) hemicraniectomy performed according to the decision of the treating physician independent of study participation, (3) available postoperative imaging data measuring hemicraniectomy diameter, and (4) completed follow-up assessment of functional outcome conducted after 12 months. Patients with concomitant acute contralateral and/or infratentorial infarction or additional acute traumatic brain injury were excluded. The timing of hemicraniectomy and choice of the surgical technique  were left to the discretion of the treating neurosurgeon with a reference to the current guidelines .After study inclusion, sociodemographic factors, clinical parameters , pre-morbid functional status, vascular risk factors as well as surgical and medical treatment data were documented in a case report form . AdditioThe primary outcome was defined as the functional status according to the modified Rankin Scale score (mRS) after 12 months. Clinical outcome was dichotomized as mRS 0–4 versus 5 and 6 according to the definition of the pooled analysis of the three European hemicraniectomy RCTs . SecondaTIFT (Tension Imaging and Fiber Tracking) software [Neuroradiological parameters were processed centrally and blinded to functional outcome on the basis of CT or MRI scans on admission and after neurosurgery using software , 17, 19.software . In contTo simplify the measurement of the hemicraniectomy diameter on postoperative imaging data, the bone flap was considered as an ellipse oriented in sagittal axis see Fig. : First, All patients were dichotomized in two groups based on the diameter of the bone flap according to the larger major axis defining diameter ≤ 14 cm as “standard hemicraniectomy” (HC ≤ 14) and > 14 cm as “large hemicraniectomy” (HC > 14) , 14, 21.2 test were used as appropriate to identify differences between the two treatment-groups (HC ≤ 14 vs. HC > 14). To prevent confounding by indication, i.e., performing larger diameter of hemicraniectomy for larger infarctions, linear regression analysis between infarct volume at study inclusion and diameter of hemicraniectomy was performed. Using receiver-operating characteristic (ROC) analysis, threshold levels of hemicraniectomy diameter were calculated to evaluate the cut-off suggested by current guidelines of 14 cm. Diameter of bone flap and parameters of neurosurgery and conservative therapy were entered in a binary logistic regression model to evaluate their impact on functional outcome adjusted for age and infarct volume on admission. Results were expressed as odds ratios with 95%-Confidence Interval . The level of significance was defined as p < 0.05.Statistics were performed using the SPSS 26 software package . Descriptive analyses were calculated for all variables. Student´s t test, Mann–Whitney U test, or χ2 vs. HC > 14: 119.4cm2, p < 0.001) were larger than in the HC ≤ 14 group  were female, mean age (SD) was 54.5 (11.0) years, and 94 (72.3%) patients were younger than 60 years at study inclusion. One year after hemicraniectomy 27 (20.8%) patients had a mRS of 0–3 and 79 (60.8%) patients had a mRS of 0–4. 29 (22.3%) patients had died before the 12 months follow-up. Causes of death during hospital stay  were transtentorial herniation (N = 9), cardiac arrest (N = 2), pneumonia (N = 1), pulmonary embolism (N = 1), and unknown (N = 2). Causes of death during the follow-up period after discharge were not assessed. Depending on the decision of the operating neurosurgeon 88 (67.7%) patients underwent standard hemicraniectomy (≤ 14 cm) and 42 (32.3%) patients were treated by large hemicraniectomy (> 14 cm). Large hemicraniectomy was performed at 10 out of 30 study centers and 30 out of 42 (72%) cases were performed at 3 study centers. No significant differences in baseline demographic or clinical characteristics were found between the two hemicraniectomy groups  = 0.216, p = 0.643), suggesting an absence of confounding by indication and the unselected use of large over standard hemicraniectomy. In addition, ROC analyses did not determine a certain hemicraniectomy diameter other than 14 cm that could predict outcome , in-hospital mortality , or mortality after 12 months  with a sensitivity or specificity higher than chance.Neurosurgery-related parameters and complications regarding hemicraniectomy or intensive care are shown in Table In multivariable binary regression analyses with outcome as dependent variable, adjusted for age, volume of infarction, number of complications, frequency of wound healing disorders, frequency of subdural hematomas, differences in conservative therapy, and type of duraplasty performed, the diameter of hemicraniectomy was no significant predictor of outcome Table . The addDespite early prophylactic hemicraniectomy almost 20% of patients who suffer a malignant middle cerebral artery infarction still die. Most deaths occur early and are due to herniation which raises the question if some patients might benefit from a larger hemicraniectomy or if a larger hemicraniectomy in general could be beneficial . None ofMortality in this study population was similar compared to patients treated with hemicraniectomy in the pooled analysis of RCTs in younger patients with malignant infarction . FunctioSince infarct volume can predict outcome after decompressive hemicraniectomy , the assIn RCTs, the rates of hemicraniectomy-related complications were comparatively lower  , than inIn our cohort osmotherapy and muscle relaxation were applied more frequently in the standard hemicraniectomy group. Although both treatments had no impact on functional outcome in multivariable analyses, the increased use of osmotherapy and muscle relaxation in patients with smaller hemicraniectomies may be indicative of a poorer control of intracranial pressure compared to patients with larger bone flaps.Despite the strengths of a prospective multicenter registry, our study is not without limitations: it is a non-randomized study and the decision of timing, diameter, and technique of the hemicraniectomy was left at the discretion of the treating neurosurgeon. Hemicraniectomy with duraplasty as a procedure was not standardized , neitherIn conclusion, our results do not provide evidence that large hemicraniectomy is beneficial regarding functional outcome or mortality as compared to standard hemicraniectomy in unselected patients with malignant middle cerebral artery infarction treated by hemicraniectomy. Although our results indicate that standard hemicraniectomy may be associated with less complications and is sufficient in most cases, selected patients may still benefit from a larger diameter hemicraniectomy to achieve the best possible outcome. This relevant question should be addressed in a randomized controlled trial.Supplementary file1 (DOCX 32 KB)Below is the link to the electronic supplementary material.