New dual temperature and strain sensor has been designed using eccentric second-order fiber Bragg gratings produced in standard single-mode optical fiber by point-by-point direct writing technique with tight focusing of 800 nm femtosecond laser pulses. With thin gold coating at the grating location, we experimentally show that such gratings exhibit a transmitted amplitude spectrum composed by the Bragg and cladding modes resonances that extend in a wide spectral range exceeding one octave. An overlapping of the first order and second order spectrum is then observed. High-order cladding modes belonging to the first order Bragg resonance coupling are close to the second order Bragg resonance, they show a negative axial strain sensitivity (−0.55 pm/με) compared to the Bragg resonance (1.20 pm/με) and the same temperature sensitivity (10.6 pm/°C). With this well conditioned system, temperature and strain can be determined independently with high sensitivity, in a wavelength range limited to a few nanometers. The use of femtosecond laser pulses has emerged as a competitive technology for Fiber Bragg Gratings (FBGs) inscription. The main advantage of this kind of lasers is the capability to engrave directly a variety of structures in almost all types of optical materials. Indeed, it has been demonstrated that femtosecond laser beam can be focused below the diffraction limit such that structures as small as 240 nm can be obtained145648411Beyond their use for lasers and telecommunication applications, the integration of FBGs as sensors has become almost a routine nowadays. Nevertheless, gratings that can be used in harsh environment with reliable self-compensation sensing solutions are still relevant to produce, especially for structural health monitoring, nuclear and oil & gas industries1313In this work, we demonstrate the production of first- and second-order eccentric FBGs with the 800 nm infrared (IR) femtosecond point-by-point (PbP) inscription technique. Our purpose is to study the sensing properties of the Bragg and cladding modes resonances in a wide spectral range (300 nm). These cladding modes are highly influenced by the surrounding medium. Hence, below the cut-off wavelength (corresponding to the resonance for which the effective refractive index matches the one of the surrounding medium), cladding modes are radiatedAs a result of these couplings, it is possible to monitor  both second order Bragg peak and high order cladding modes. While both kinds of peaks exhibit a similar temperature sensitivity , their axial strain sensitivity is completely different . These features yield one of the best-conditioned systems reported so far. Other important practical benefits result from the flexibility of production and the inherent grating resistance to high-temperature environments.The production of eccentric FBGs is carried out with the direct PbP inscription technique and 800 nm femtosecond pulses delivered by Spitfire pro Spectra-Physics amplifier of 120 fs duration and 1 kHz repetition rate. The experimental setup and inscription process were described in previous works4C) in the spectral range [1300 nm–1600 nm] covered by the broadband optical source (Amonics Superluminescent Diode ASLD-CWDM-5-B-FA) and spectrum analyser (Yokogawa AQ6370) used in this work. In the following, we report the behaviour of 3 gratings inscribed in standard single mode optical fibre (Corning SMF28) with different periods 550 nm, 633 nm and 1096 nm and the same eccentricity (2 μm). The spacing between these points corresponds to the grating period, which can be controlled by correlating the speed of the translation stage to the repetition rate of the laser. To produce eccentric gratings, the fiber was first shifted 2 μm off-center in the horizontal direction (x direction as shown in B) occurring at 1591 nm, and at its left side, in a very huge spectral range, cladding modes resonances, which are drastically attenuated around λC = 1345 nm (cut-off wavelength) indicted by a dashed line. In FBG2, we can only see cladding modes resonances down to λC = 1548 nm, because the Bragg resonance is out of the spectral range (1831 nm). FBG3 shows a similar transmitted amplitude spectrum as FBG1, with 1585 nm second order Bragg resonance and 1341 nm cut-off wavelength.It is worth mentioning that the spectra are composed by four types of cladding modes TE0m, TM0m, HElm, and EHlm, where “l” is the azimuthal order and “m” is the order of a mode. The radial (Er) and azimuthal (Eϕ) electric fields are null for TE0m and TM0m modes so that they are polarization-independent. However, both HElm and EHlm modes are polarization-dependent since they combine axial and transverse components. As a result, a x-polarized core mode couples to the even HElm and TE0m modes while a y-polarized one couples to the odd EHlm and TM0m modes. Highest order modes EHlm and HElm are dominantly radially and azimuthally polarized, respectivelyjth cladding mode resonance resulting from core mode coupling to cladding appears at a wavelength Each neff,core and jth cladding mode and Where m is the grating order, neff,core = 1.4467, the cut-off wavelength in air occurs around 1345 nm for FBG1, at 1545 nm for FBG2 and at 1340.7 nm for the second order grating FBG3. These values are in good agreement with the reported experimental results  deposited on the fiber surface. A sputter coater was used for this purpose. The coated gratings were then cured at 200 °C during 6 hours for improved gold adhesionThe cut-off wavelength can be easily calculated from  results . We mustAccording to other studiesIt has been previously demonstrated that in tilted2124neff,clad. We can see clearly an interval of neff,clad between 0.95 and 1.28 where the dispersion in the measurements increases for FBG1 and FBG3. In fact this region partly shown in the inset of neff,clad.4The linear regression of the experimental data for FBG2 yields:Kε is the strain sensitivity expressed in pm/με.where neff,clad = 0.1 in According to neff,clad) coexisting with the Bragg resonance. In the following, we will study axial train and temperature sensitivities of this eccentric second-order grating.Therefore, gold-coated FBG3 is a perfect illustration of the presence of very high cladding modes (with very low 1) and the nearest high order cladding mode resonance (Peak2 at λ2) in the gold-coated eccentric second order FBG3. To decouple between temperature and strain effects, we propose to use here the second order Bragg resonance  satisfy the good conditioning of the matrix inversion:B and cladding mode peak at λ2 undergo opposite shifts when the axial strain increases. The linear regression of the experimental data depicted in Kε1 = 1.20 pm/με for the Bragg peak whereas the one for high order cladding mode is Kε2 = −0.56 pm/με. This negative value is highly different from the Bragg peak sensitivity, which completely fulfill the condition of The calibration curves for temperature and strain measurements of FBG3 allow extracting the sensitivities coefficients. In KT1 and KT2, respectively).For temperature calibration, the slope of the linear regression for the experimental wavelength shift versus temperature data  gives alFor sensing application, a performance factor to compare the efficiency of decoupling methods is proposed in ref. Eccentric FBGs were produced by point-by-point direct writing technique with femtosecond pulses. The flexibility and tunability of this inscription technique provide gratings with different pitches, which gives the possibility to study a very wide spectral range transmission amplitude spectrum providing access to different cladding mode orders. We experimentally demonstrate that the axial strain sensitivity of the cladding modes decreases linearly with the effective refractive index of the mode. For very high cladding mode orders that are kept in the amplitude spectrum thanks to a gold overlay, negative values can even be reached. This high differential strain sensitivity was exploited to implement a sensor for independent temperature and strain measurements from a single eccentric second-order grating. This sensor considers the sensing properties of the Bragg grating core mode and one very high-order cladding mode. We show that this cladding mode exhibits a similar temperature sensitivity (10.6 pm/°C) but a strongly different strain (−0.55 pm/με) sensitivity compared to the Bragg peak (10 pm/°C and 1.20 pm/με respectively). These properties are considered ideal for dual sensing purposes.How to cite this article: Chah, K. et al. Negative axial strain sensitivity in gold-coated eccentric fiber Bragg gratings. Sci. Rep.6, 38042; doi: 10.1038/srep38042 (2016).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


The process by which sheared suspensions go through a dramatic change in viscosity is known as discontinuous shear thickening. Although well-characterized on the macroscale, the microscopic mechanisms at play in this transition are still poorly understood. Here, by developing new experimental procedures based on quartz-tuning fork atomic force microscopy, we measure the pairwise frictional profile between approaching pairs of polyvinyl chloride and cornstarch particles in solvent. We report a clear transition from a low-friction regime, where pairs of particles support a finite normal load, while interacting purely hydrodynamically, to a high-friction regime characterized by hard repulsive contact between the particles and sliding friction. Critically, we show that the normal stress needed to enter the frictional regime at nanoscale matches the critical stress at which shear thickening occurs for macroscopic suspensions. Our experiments bridge nano and macroscales and provide long needed demonstration of the role of frictional forces in discontinuous shear thickening. et al. show that shear thickening occurs at the transition from lubricated contacts to frictional contacts at a single-particle level, which can be linked to the change in macroscopic rheology.Shear thickening characterizes liquid suspensions of particles that reversibly solidify subject to stress. Here, Comtet  Dense suspensions of solid particles immersed in a Newtonian solvent display complex flow properties. Shear thickening, where the resistance to flow increases when the dispersion is stirred is one of the most intriguing behaviour1346Despite an extensive characterization of discontinuous shear-thickening transitions at the macroscale, there is still no clear understanding of the microscopic mechanisms at play in this transition, principally owing to the challenges associated with quantitative frictional measurements at the nanoscaleA long-standing view is that thickening is driven by hydrodynamic and Brownian forcesTo get around this issue, recent works14At this stage, this picture and the role played by frictional forces have been validated through numerical simulations but only indirectly through experiments at the level of the suspension26In the present work, we bridge this gap between nano and macro-scales. Taking advantage of quartz-tuning fork based atomic force microscope with subnanonewton resolution, we build upon state of the art procedures171921We present in During a typical experiment, the attached particle is immersed in solvent and brought into contact to another bead fixed on the substrate, while monitoring the force profile . FurtherfN≈31 kHz and fT≈17 kHz, corresponding to the excitation of both normal (blue arrows) and shear modes of the tuning fork (red arrows), as shown in To measure simultaneously normal and tangential force profiles between the two approaching particles, we simultaneously excite the tuning fork via the piezo-dither at two distinct resonance frequencies N) and tangential (T) modes  will lead to shifts in the resonance frequency of the oscillator (comparing black and red resonance curves in F (N m−1) is proportional to the shift in the resonance frequency δfi (Hz) according toWe now detail how to obtain force profile for each normal (T) modes . When ex−1) are the spring constants, respectively, associated with normal (N) and tangential (T) oscillation modes, ei corresponds to the unit vector along direction i.where i=T):We can then express the frictional forces applied on the bead as the sum of viscous-like friction force  and solid friction force  is the oscillating speed, γ (kg s−1) is a viscous-like friction coefficient and the second term Fs [N] characterizes the solid friction force, only dependent of the sliding direction vi/||vi||. The friction forces Fs are assumed to be velocity independent as experimentally confirmed a posteriori. Over one oscillation period, all friction forces in where ai at resonance requires the external excitation force Fext (due to the piezo dither) to be equal to the to the sum of all dissipative forces FD. As the external force Fext is directly proportional to the excitation voltage Eext, the sum of all dissipative forces FD is directly measured by tracking the excitation voltage necessary to keep a constant oscillation amplitude  is the typical speed of the oscillating particle, z (m) is the distance between the two no-shear planes and R (m) is an equivalent bead radius. The intersection of the red line with the horizontal axis defines the hydrodynamic zero (z=0), which defines the absolute position of the no-shear planes between the two objects  and (ii) z<0 hard contact (light red). It is noteworthy that for confinement below ≈ 3 nm, we observe a deviation from Stokes hydrodynamics with a regularization of the hydrodynamic divergence, possibly stemming from elastohydrodynamic interactions1325z<0 may be due to viscoelasticity of the PVC particles.where sity see , v=aω (m∂FN/∂z (N m−1) shown in ∂FN/∂z>0) before contact between the two particles . These repulsive forces vary steadily and smoothly with distance, whereas normal dissipation is dominated by hydrodynamics during the approach (19F≈exp(−z/λ) with λ≈4 nm , due to the presence of asperities on one of the bead surface . The independence of sliding friction with speed validates a posteriori our choice for the form of On a critical normal load μ=0.45±0.2, in very good agreement with the macroscopic friction coefficient of PVC on PVCFinally, we show in We now come back to the macroscale behavior of non-Brownian suspensions.σ and the measured shear rate σC . Those τC are measured for approximatively the same range of relative velocities between the two particles. In the macroscopic experiments, the relative velocity between two particles can be approximated as −1. In the AFM experiments, the normal root mean square (RMS) speed is ∼30–200 μm s−1 and the tangential RMS speed 150–800 μm s−1.Let us underline that z<2 nm), they do not contribute to the observed shear-thickening transition. Indeed, we find that the critical shear stress σC at the shear-thickening transition varies as a function the contact forces , Dinch can dissolve the PVC particlesAs a plasticizer for PVC particles, we use 1,2-cyclohexane dicarboxylic acid di-isononyl ester (Dinch) supplied by BASF. This organic liquid Dinch slightly disolves the outer part of the particles and creates a polymer brush around them. This brush enables stabilization of the suspension due to steric repulsion−1 at 25 °C) was achieved by mixing two different viscosity standards (55.7 and 29.0 mPa s−1). Resulting viscosity was checked in a shear rate range from 1 to 100 s−1 for different temperatures. Same viscosity at 25 °C and same temperature dependence of viscosity (range 20–25 °C) were found between plasticizer and obtained mineral oil.Degree of plasticization can be changed by using a mix of mineral oil and plasticizerConcerning PVC, we report results  for three different plasticizing liquids: (1) 100 vol.% plasticizer, (2) 90 vol.% plasticizer+10 vol.% mineral oil, and (3) 67 vol.% plasticizer and 33 vol.% mineral oil.Tg=80 °C), the original shape and surface topography of the particles is preserved in-situ SEM (FEI Nova NanoSEM 450) (see PVC and cornstarch particles are glued to the etched tungsten tip of the tuning fork using SEMGLU from Kleindiek and a nanomanipulation station 450) see . Measureγi the viscous friction coefficient and We consider below the equation of motion for the tuning fork close to its resonance frequency, in the presence of both viscous and sliding friction. We recall that the friction force on force . In its ω is the excitation frequency, m the equivalent mass and ki the equivalent stiffness of the mode i∈{N, T}. γ, F will vary with position. The factor 2/π stems from the first Fourier coefficient of the square-like shape of the solid friction force. From a0, the quality factor Q=mω0/γ characterizing viscous dissipation and the solid friction force where a0 can then write as the sum: CVext, where C is a factor calibrated at the beginning of each experiment. When the two particles are distant, we get a0 gives us a direct measure of the sum of all forces acting on the tuning fork as CVext to obtain an amplitude a0 typically equal to 1–50 nm. Both shear and normal modes of the tuning fork can be excited at the same time by summing the two excitation voltage at each frequencies  keeps the oscillation amplitude aT of the tangential mode constant, allowing a direct measure of the frictional forces by monitoring the amplitude of the excitation voltage ET. A fixed amplitude of the excitation voltage EN is applied to the normal mode and dissipation is measured by monitoring the oscillation amplitude aN. The electronic lock-in and phase-locked loops s are implemented using a Nanonis from (SPECS Zurich) and a HF2LI Lock-in Amplifier (Zurich Instrument).The external excitation force necessary to keep a constant oscillation amplitude quencies . Owing tρPVC=1.38 g cm−3, the density of Dinch ρDinch=0.95 g cm−3 and the density of mineral oil ρoil=0.84 g cm−3. Suspensions are stirred 5 min at 1,000 r.p.m. using a Dispermat LC55 (VMA Getzmann), to ensure good dispersion state. Samples were freshly mixed for each experiment. This protocol was found to produce reproducible samples. The solid volume fraction of the suspension is defined as the volume of particles divided by the total volume: We prepare our dispersions by weighting a given amount of PVC particles, a given amount of Dinch and a given amount of mineral oil. The solid fractions are then calculated knowing the density of PVC D=40 mm, angle=2°, truncation gap=54 μm). A logarithmic stress sweep (50 s per point) between 1 and 1,000 Pa (10 points per decade) was performed to measure the flow curve. Flow curve obtained matches the viscosity found using ‘peak holds’ of shear rate (flow steady state is reached within 10 s). No wall slip was measured in these experiments. This was checked indirectly by measuring velocity profiles using ultrasounds in Couette cells.Rheology was measured using a stress-controlled DHR-3 rheometer (TA Instruments) equipped with a smooth cone  equipped with a hatched plate (diameter D=40 mm) similar to that in previous worksη)/d(log σ) reaches 1 .Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figures and Supplementary Note 1


This may subsequently impact insect herbivory. In sclerophyllous forests insects have developed strategies, such as preferentially feeding on new leaf growth, to overcome physical or foliar nitrogen constraints, and this may shift under climate change. Few studies of insect herbivory at elevated [CO2] have occurred under field conditions and none on mature evergreen trees in a naturally established forest, yet estimates for leaf area loss due to herbivory are required in order to allow accurate predictions of plant productivity in future climates. Here, we assessed herbivory in the upper canopy of mature Eucalyptus tereticornis trees at the nutrient-limited Eucalyptus free-air CO2 enrichment (EucFACE) experiment during the first 19 months of CO2 enrichment. The assessment of herbivory extended over two consecutive spring—summer periods, with a first survey during four months of the [CO2] ramp-up phase after which full [CO2] operation was maintained, followed by a second survey period from months 13 to 19.Climate change factors such as elevated atmospheric carbon dioxide concentrations  compared to old or fully expanded leaves (less than 2 % leaf area loss). This preference of insect herbivores for young expanding leaves combined with discontinuous production of new foliage, which occurred in response to rainfall, resulted in monthly variations in leaf herbivory. In contrast to the significant effects of rainfall-driven leaf phenology, elevated . e[CO2] responses of herbivores on mature trees may only become apparent after extensive CO2 fumigation periods.In the studied nutrient-limited natural The online version of this article (doi:10.1186/s12898-016-0102-z) contains supplementary material, which is available to authorized users. Furthermore, some studies suggest modulation of plant hormone signalling and induced plant defence at e[CO2] [2] can increase plant net primary production (NPP)  , 10. Clit e[CO2] –13. It hon (NPP) , 15 and on (NPP) , 17 or won (NPP) , or alsoEucalyptus (Myrtaceae) is both an ecologically and economically important tree genus in many parts of the world —this is to compensate for the dilution of leaf nitrogen [2] may result in an additional 17–40 % of leaf damage compared to current levels [2], the survival of herbivorous insects may be reduced while developmental time is often increased [2] may increase leaf damage caused by individual insects to forest trees, however, the abundances of insects in these forests may be reduced due to the negative effects of e[CO2] on insect survival and development. Overall this may result in no net change of leaf damage to trees at e[CO2].Increased consumption of leaves, or compensatory feeding, is often observed in herbivorous insects as a response to plants grown under e effects on frass deposition or LAI changes within the first 2 years of EucFACE were found, suggesting that insect herbivory and canopy processes may not be impacted by early stages of [CO2] fumigation at EucFACE.It has previously been demonstrated that the production of insect herbivore excrements (or frass), a crude proxy for insect abundance and herbivory, increased after large rainfall events during the spring and summer at the periment . This inperiment , suggest2] may change leaf phenology and thereby resource availability for herbivores. It may also alter the preference of insect herbivores for different leaf stages if the relative palatability of young expanding versus fully expanded (mature) or old leaves changes under e[CO2]. Any change in the consumption of young expanding leaves may therefore affect the recruitment of new leaves in the forest canopy, and place stress on plants. For new leaves, LAI measurement methods may struggle to discriminate between insect removal of leaf area and reductions in NPP. This can result in an incorrect estimate and under-evaluation of NPP of forests, particularly if climate change factors alter the herbivory of new leaf production.The measurement of frass deposition onto the woodland floor does not reveal which leaf age class experiences most damage from herbivory. Furthermore, e and rainfall patterns on these processes in a mature, evergreen canopy of this tree species forming a naturally established woodland at the EucFACE experimental site. We hypothesised that rates of insect herbivory would respond to new leaf production which again would vary across time based on rainfall. It has previously been demonstrated that rainfall is the key driver of Eucalyptus leaf phenology, including at the study site [2] conditions within a mature Eucalyptus canopy forming a woodland for two spring and summer periods at which herbivore activity was observed to be highest in the first and second year of EucFACE [E. tereticornis [2] during the first 2 years of EucFACE.This study investigated the relationship between insect herbivory and leaf phenology of udy site , 39, 40. EucFACE ; (2) proticornis , and (3)Eucalyptus free-air CO2 enrichment (EucFACE) experiment located within a native Cumberland Plain woodland remnant  in treatment rings was increased by 30 µmol mol−1 every month until February 2013; thereafter diurnal [CO2] targets within the treatment rings were 150 µmol mol−1 above ambient levels of ~400 µmol mol−1. Rainfall was recorded using automated tipping bucket gauges  located 23.5 m above the ground on the central tower in three rings. Data from these sensors were logged every 15 min using CR3000 data loggers .Six large 25 m diameter rings with a height of 28 m above ground, extending above the tree canopy, were constructed amongst the vegetation of the site. Adjacent to each ring stands a high canopy crane with a person basket that allows access to the canopy from above. Each ring also contains a central scaffold tower. Three rings were fumigated diurnally with COlgorithm , while tEucalyptus trees display a homogeneous pattern of herbivory throughout the crown , month and their interaction. The random model included ring with tree as a nested factor to account for repeated measures. An autocorrelation function was used in order to test for temporal autocorrelation within years, and an autoregressive moving average (ARMA) correlation structure was employed to model dependence among observations of leaf consumption and leaf production across months using a first-order autoregressive structure (AR1)  did not alter the timing of flush production between year 1 and 2 . Strong positive correlations were observed between the number of expanding leaves present and leaf consumption .The number of new young leaves produced by trees and lost to herbivory did not differ as a result of CO2] was gradually increased from ambient conditions to +150 µmol mol−1, while in the second year, e[CO2] was maintained at 550 µmol mol−1. The two monitoring periods included two major leaf production events, one in each year during spring and summer. Independent of [CO2], consumption of young expanding leaves was very high and decreased to very low levels once leaves were fully expanded. The drastically higher levels of herbivory on young leaves drove monthly variations in overall leaf damage by insect herbivores due to the variation in leaf production. Furthermore, e[CO2] did not affect damage due to herbivory and total leaf consumption. This was in line with our expectation that we would not detect compensatory feeding because of a previous study in which we detected that concentrations of foliar nitrogen and total phenolics at the EucFACE site were not affected by CO2 fumigation over the first 2 years of EucFACE [2] exposure by retrieving nutrient reserves   . Herbivoaves [2]  displayeaves [2] . This hiaves [2] .E. tereticornis in a native woodland observed in this study is within the range observed in other Australian systems. For example, in an Australian rainforest insect herbivore damage on young expanding leaves ranged between 10 and 30 % depending on tree species, and this fell to less than 5 % once leaves matured [2]  . A preving guild .2 of two key leaf chewing insect herbivores found at the EucFACE site had previously been tested on young E. tereticornis trees in greenhouse experiments. The cup moth Doratifera quadriguttata (Lepidoptera: Limacodidae) and the leaf beetle Paropsis atomaria (Coleoptera: Chrysomelidae), both experienced negative effects of e[CO2] such as increased mortality, extended developmental times and reduced pupal weights, while both species also displayed signs of compensatory feeding [E. tereticornis trees at EucFACE under CO2 enrichment. In other forests undergoing CO2 fumigation e[CO2] has been observed to either decrease [2] across a variety of forest types may be due to the complexity in interactions between biotic and abiotic factors which impact insect herbivores and therefore herbivory.The responses to eCO feeding –38. Howedecrease , 64, caudecrease , or incrdecrease , 67 the Glycaspis sp. and Cardiaspina fiscella was detected on E. tereticornis after March 2014 , and signs for compensatory feeding were detected in one of these three species, Glycaspis sp.  as a result of a carbon fertilisation effect [2 fumigation at the EucFACE site we did not observe an increase in leaf production. This may indicate that mature E. tereticornis trees within the site are limited by water and nutrient availability [2] may also result in increased respiration in the ecosystem  are difficult to make under field conditions owing to the complex interactions between plants, insect herbivores and their antagonists. This uncertainty in insect herbivore responses hinders the ability to accurately determine model-specifications of their response to climate change  responses in concentrations of foliar nitrogen and total phenolics in insect frass [2] in altering insect herbivory and herbivore abundances is important in predicting the impacts of climate change variables on insect herbivore population dynamics in forests and plantations.Predictions about damage inflicted by insect herbivores at e[COe change . Contrarct frass . Howeverct frass , and thict frass , can hav


Drosophila. Despite knowledge gathered in the past on the peripheral perception of taste, little is known about the identity of taste interneurons in the brain. Here we show that hugin neuropeptide-containing neurons in the Drosophila larval brain are necessary for avoidance behaviour to caffeine, and when activated, result in cessation of feeding and mediates a bitter taste signal within the brain. Hugin neuropeptide-containing neurons project to the neurosecretory region of the protocerebrum and functional imaging demonstrates that these neurons are activated by bitter stimuli and by activation of bitter sensory receptor neurons. We propose that hugin neurons projecting to the protocerebrum act as gustatory interneurons relaying bitter taste information to higher brain centres in Drosophila larvae.Bitter is a taste modality associated with toxic substances evoking aversive behaviour in most animals, and the valence of different taste modalities is conserved between mammals and  Bitter taste evokes aversive behaviour in animals, but little is known about the central nervous system mechanisms that convey this taste modality. Hückesfeld et al. identify a set of second order neurons in Drosophila that contain hugin neuropeptide and are responsible for conveying bitter taste to the protocerebrum. Drosophila1234Drosophila 60 gustatory receptor genes encode 68 gustatory receptors67Drosophila share no homology to mammalian taste receptors, the strategy used in both to detect a taste molecule, process its information and the valence of aversive bitter and appetitive sweet stimuli share similarities10Drosophila were characterizedDetailed knowledge exists on the anatomical distribution and function of gustatory receptors in mammals and Drosophila larvae overlap with that of bitter gustatory receptor neurons (GRNs) expressing the caffeine receptor GR66a1516Drosophila, GR66a was shown to represent a bitter receptor for detection of caffeine916Drosophila larvae, artificial activation of GR66a positive neurons leads to aversive behaviourA candidate for conveying bitter taste from the SEZ to higher brain centres are neurons that express the hugin neuropeptide13Drosophila larval brain.Using classical two-choice behavioural experiments, electrophysiological measurements as well as calcium imaging analysis, we now show that hugin neurons relay caffeine as well as other bitter taste signals from sensory neurons to the protocerebrum, acting as bitter taste interneurons in the We first asked whether the hugin neurons make contacts with caffeine responsive GR66a neurons. Using the GFP reconstitution across synaptic partners (GRASP) approachshibireTS) in the hugin neurons, which leads to a block of synaptic release in a temperature dependent manner. The loss of proper bitter aversion still persisted (Activating the hugin neurons causes the larvae to stop feeding and move out of a strongly appetitive food source (yeast)ersisted .We next asked if hugin neurons were involved in other taste modalities. We first tested high salt (2 M NaCl), which is very aversive for larvaeAs the hugin neuronal cluster is composed of different classes with different projection targets13Calcium Modulated Photoactivatable Ratiometric Integrator), that allows monitoring of calcium activity in intact animals. Calcium activity and simultaneous presence of ultraviolet-light (405 nm) lead to an irreversible conversion from green to red fluorescence of the neurons of interestDrosophila, reflecting an interaction between pathways involving different taste modalities. This cross-regulation might be a general strategy to efficiently detect distinct taste modalities, since in case of the huginPC neurons, a sweet taste stimulus would inhibit the activity of bitter interneurons.To further investigate the connection between bitter taste and hugin neurons, we asked if the huginPC neurons could be activated by caffeine using CaMPARI , and induction of a wandering-like behaviourDrosophila. Inhibition of huginPC neurons when larvae are tasting salt might be due to a different processing circuit for different concentrations of salt and the decision to either take up low doses or reject high doses.Bitter compounds may be able to inhibit the sweet-sensing response to ensure that bitter taste cannot be masked by sweet tasting food. This provides an efficient strategy for the detection of potentially harmful or toxic substances in food262129Drosophila, but may also help in assigning a potentially novel role of its mammalian homologue, Neuromedin U, in taste processing.Taken together, we propose that hugin neuropeptide neurons projecting to the protocerebrum represent a hub between bitter gustatory receptor neurons and higher brain centres that integrate bitter sensory information in the brain, and through its activity, influences the decision of the animal to avoid a bitter food source. The identification of second order gustatory neurons for bitter taste will not only provide valuable insights into bitter taste pathways in TSWild type (OrgR) crossed to UAS-dTrpA1 (Bloomington #26263) served as control in Adult flies and larvae were kept on 25 °C under 12 h light/dark conditions. For electrophysiological and food intake experiments 4 h egg collections were made on apple juice agar plates containing a spot of yeast–water paste. After 48 h, larvae were transferred into food vials containing lab standard fly food. For other experiments  larvae were raised in vials containing standard fly food with a spot of yeast for 4 days. All larvae used for the experiments were 98±2 h old. Only feeding third instar larvae were used for the experiments.[1118]).For HugPC-Gal4 line, a 544 bp Hugin fragment 155 bp upstream of the ATG was amplified with primer1 (AAG GGT TTG GTT TAA TTT ATT TAT GTC ATA) and primer2 (GAG CCT GAT TAG GTC CCT GAT GTT TAA ACT T) and cloned into pCaSpeR-AUG-Gal4-X vector /#larvaetotal.To measure the preference index of larvae towards given appetitive or aversive substrates, 9 mm diameter petri dishes were filled with 20 ml warm water agar . After 20 min of air drying half of the agar was cut away and discarded. Compounds  were diluted in warm agar in the given concentration until the agar fluid was clear, and filled in the other half of the petri dish (10 ml). After air drying again for 20 min, petri dishes were prewarmed in the 32 °C incubator 1.5 h prior to the experiment. All two-choice experiments were performed at 32 °C for comparability between all genotypes. For each experiment 30 larvae were taken out of standard fly food and washed with tap water. Larvae were then placed on the water side of the two-choice dishes and videotaped for 20 min. Videos were processed with FIJI (ImageJ) and analysed using a custom written script for FIJI. Analysis of PI values started 60 s after the start of the experiment to ensure proper tracking of larvae due larval accumulation at the beginning by placing them on the pure agar side. PIFor testing response to an attractive odour (apple vinegar), a one-choice assay was performed. Agar plates were used (as described earlier for two-choice petri dishes) and placed into the incubator at 32 °C for 1.5 h. Larvae were videotaped at 32 °C for 5 min, and then an Eppendorf cup (1.5 ml) with filter paper soaked with apple vinegar was placed on one side of the water agar plate above the larvae such that they were not able to reach the odorant source. Movement of larvae was analysed using the custom made FIJI macro.Apple juice agar plates were prepared with a spot of red yeast paste in the middle of the plate. Plates were then placed in incubators precooled to 18 °C or prewarmed to 32 °C for 2 h. After 30 min starvation, five larvae were transferred on top of the yeast paste of a plate and videotaped for 20 min. After 20 min of videotaping, larvae were transferred into a small cell strainer and washed with 60 °C hot water. Larvae were then transferred to glass slides for photo documentation and analysed with the open source software FIJI (ImageJ) and a custom written analysis macro, which calculated the percentage of the red stained surface of the body compared with the whole body of the larva. To calculate the fold change of food intake from 18 to 32 °C, the value of all 32 °C values was divided by the mean value of all 18 °C values.Third instar larvae were dissected in 35 mm petri dishes coated with 5 ml two-component silicone (Elastosil RT). Larvae were pinned down dorsal side up at the anterior and posterior end using 77 μm thick sharp etched tungsten needles. The larva was cut open longitudinally along the dorsal midline and the cuticle was pinned aside with 40 μm tungsten needles. Interior organs like fat body, intestine or salivary glands were removed except for the cephalopharyngeal skeleton and CNS with attached nerves of interest. Eye and leg imaginal discs were also removed. A transversal cut of the cuticle was performed beneath the CNS to reveal the AN. Nerves not needed for the respective recording were cut. A piece of thinned Parafilm was placed beneath the nerve of interest. This nerve was isolated from the surrounding solution with two adjacent jelly pools. Motor output of the AN was measured using custom made silver wire electrodes connected to a preamplifier . The preamplifier was connected to a four-channel amplifier/signal conditioner . All recorded signals were amplified  and filtered (bandpass: 0.1–3 kHz). Recordings were sampled at 20 kHz. Data were acquired with Micro3 1,401 A/D board (Cambridge Electronic Design) and Spike2 software (Cambridge Electronic Design).High-power LED of 405 nm  Mounted LED, 1,000 mA, 410 mW) was driven with a LED controller  and positioned 18 cm above the solution with the larva. PCR plate of 96-well was filled with 50 μl containing the given taste stimuli in tap water. Larvae were placed into the solution for 2 min and then ultraviolet light was applied for 30 s.L-lysine  coated cover slide with a drop of PBS. All z-stacks of the HugPC neurons were aquired using a ZEISS LSM 780 Laser scanning microscope with LCI Plan-Neofluar 25 × /0.8 Imm Korr DIC M27. For quantification of green to red photoconversion maximum intensity projections of the acquired z-stacks were used and a portion of the cytoplasmatic region of each cell was analysed to obtain data for green and red fluorescence intensity. Red fluorescence intensity was divided by green fluorescence intensity to get Fred/Fgreen ratio. A ‘no ultraviolet light' control was included to show that scanning of the CNS without being exposed to ultraviolet light does not convert green to red fluorescence.Afterwards brains were dissected in PBS and mounted onto a Poly-Genotypes used for GFP reconstitution across synaptic partners (GRASP) methodL-lysine coated coverslide in a drop of saline. Coverslide was attached to a custom built heating device consisting of a 1.5 cm2 Peltier element for shifting the temperature from 20 to 30 °C by applying specific voltage values. Images were acquired with a Zeiss LSM 780 laser scanning microscope as time series with a speed of 781.96 ms (∼1.28 Hz) using a Zeiss LCI ‘Plan-Neofluar' 25 × per 0.8 Imm Korr DIC M27 objective dipped in the saline solution. Region of interest covered the complete HugPC neuronal ‘sprinkler-like' arborization pattern in the protocerebrum.Freshly dissected CNS of feeding third instar larvae of the genotypes UAS-dTrpA1/Hug1.2lexA; GR66a-Gal4/lexAop-GCamP6s-p10 (experiment) and Hug1.2lexA/CyO; lexAop-GCamP6s/TM3, Sb (control) were placed with the SEZ region up on a Poly-PI values of the last 5 min of the 20 min experiment and displayed as boxplots. For food intake analysis 32 °C values (% of red yeast in gut relative to whole body) were divided by the mean of all 18 °C values to gather the fold change of food intake. Fold changes were then compared with the Mann-Whitney-Rank-sum-Test. For electrophysiological data cycle frequencies were analysed at 18 °C for 60 s and 32 °C for 60 s. The fold change was calculated between 18 and 32 °C. Per larva a maximum of four temperature steps could be applied to the CNS during recordings. All fold changes of one genotype were then compared with the Mann-Whitney-Rank-Sum-Test with the other genotypes. The relative fold change is displayed as subtraction of the mean of OrgR × dTrpA1 control values from the fold change values of all genotypes (OrgR × dTrpA1 set to 0). CaMPARI data were analysed by calculating the mean Fred/Fgreen value of all eight HuginPC neurons of one larva to determine one mean Fred/Fgreen value per larva. Values were then compared with the Mann-Whitney-Rank-Sum-Test to water control.For comparison of two groups in the two choice assays Mann-Whitney-Rank-Sum-Test was used. Statistical data were acquired as cumulative The authors declare that the data supporting the findings of this study are available within the article and its  files, oHow to cite this article: Hückesfeld, S. et al. Central relay of bitter taste to the protocerebrum by peptidergic interneurons in the Drosophila brain. Nat. Commun. 7:12796 doi: 10.1038/ncomms12796 (2016).Supplementary Figures 1-3 and Supplementary Tables 1-7


For patients suffering from primary brain injury, monitoring intracranial pressure alone is not enough to reflect the dynamic intracranial condition. In our previous study, a segment of the pressure-volume curve can be expressed by the parabolic regression model with single indicator “a”. The aim of this study is to evaluate if the indicator “a” can reflect intracranial conditions.Patients with traumatic brain injury, spontaneous intracranial hemorrhage, and/or hydrocephalus who had external ventricular drainage from January 2009 to February 2010 were included. The successive volume pressure response values were obtained by successive drainage of cerebral spinal fluid from intracranial pressure 20–25 mm Hg to 10 mm Hg. The relationship between withdrawn cerebral spinal fluid volume and intracranial pressure was analyzed by the parabolic regression model with single parameter “a”.The overall mean for indicator “a” was 0.422 ± 0.046. The mean of “a” in hydrocephalus was 0.173 ± 0.024 and in severe intracranial mass with slender ventricle, it was 0.663 ± 0.062. The two extreme intracranial conditions had a statistical significant difference (p<0.001).The indicator “a” of a pressure-volume curve can reflect the dynamic intracranial condition and is comparable in different situations. A significantly larger indicator “a” with increased intracranial pressure is always observed in severe intracranial mass lesions with cerebral edema. A significantly smaller indicator “a” with increased intracranial pressure is observed in hydrocephalus. Brain computed tomography should be performed early if a rapid elevation of indicator “a” is detected, as it can reveal some ongoing intracranial pathology prior to clinical deterioration. Increased intracranial pressure was frequently observed in patients with intracranial pathology. The progression can be differentiated using the pattern of the volume pressure indicator. Continuous monitoring of intracranial pressure (ICP) is a standard procedure in patients with severe traumatic brain injury. The use of external ventricular drainage (EVD) as an ICP monitor has another important advantage: increased control over ICP through drainage of cerebrospinal fluid (CSF). Increased ICP (IICP) may indicate the worsening of intracranial pathology because of mass lesions or whole brain swelling. However, ICP monitoring alone cannot always predict any structural and functional deterioration caused by progressive growth of contusions, hematomas, brain edema or hydrocephalus. Understanding the intracranial volume-pressure (V-P) relationship can help us determine a reasonable treatment and predict the prognosis of patients with brain damage. The intracranial V-P relationship can be studied using volume-pressure response (VPR) which was defined by Miller  as the ia” to reflect the status of the P-V curve.[a” can be compared in different conditions. This study is conducted to evaluate whether the indicator “a” can accurately reflect intracranial conditions and be used as a predictive value.For patients suffering from a primary brain injury, many secondary injuries compound the initial damage during the following hours and days. Monitoring the intracranial condition and preventing secondary injury is important and indispensable. In our previous study, a segment of the P-V curve delineating abnormal ICP status can be expressed with linear, parabolic and exponential regression models in increased ICP patients. The parabolic regression model is closest to the original ICP curve and is the preferred mathematic model to represent the P-V curve. The regression model is designed with a single indicator “-V curve. The indiEthical approval for this study was provided by the Hospital Medical Research Ethics Committee for human research (97-1601B). Written informed consent was obtained from all participants.®” CSF shunting system) was connected to an ICP monitor and used for drainage of CSF. The ICP was measured by direct ventricular cannulation, and the ICP strain-gauge pressures were connected to the ICP monitor . The ICP values were obtained from the bedside ICU monitor. Once the ICP values reached 20–25 mm Hg, 1 ml of CSF was withdrawn from EVD and the corresponding change in ICP value was recorded. The withdrawn drainage of CSF continued until the final ICP value declined to 10 mm Hg and the whole drainage procedure was completed within one minute. The patients’ Glasgow Coma Scale (GCS) scores, ICP values, and the CSF drainage volume were collected. The postoperative conditions of each patient based on the Glasgow Outcome Scale (GOS) scores were evaluated at discharge and at 6 months thereafter. The Glasgow Outcome Scale is a 5-level score: 1. Dead; 2. Vegetative State; 3. Severe Disability (Able to follow commands/ unable to live independently); 4. Moderate disability ; 5. Good Recovery (able to return to work or school).The study included patients in the neurosurgical intensive care unit (ICU) with a diagnosis of traumatic brain injury, spontaneous intracerebral hemorrhage (ICH), spontaneous subarachnoid hemorrhage (SAH), and/or hydrocephalus who had external ventricular drainage (EVD) performed whose primary doctor was one of three designated neurosurgeons from January 2009 to January 2010. The initial diagnosis was confirmed by a brain computed tomography (CT) scan. Once informed consent was obtained, the patients were included in the study. Patients were excluded from this study if the EVD function was poor and early tube obstruction occurred within three post-operative days (POD). Patients who stayed in the neurosurgical ICU for less than three days were also excluded. The EVD , and X is the CSF volume (mL). The leading coefficient “a” in the parabolic regression equation acts as the indicator of the P-V curve. The end point of the CSF drainage process is around an ICP of 10 mmHg. Therefore, the constant in the parabolic regression function is defined as “10”. The different P-V curves are computed by applying parabolic regression equations to each successive VPR value. The sample coefficient of determination (r2) is calculated as a measure of the closeness-of-fit of the sample regression line to the sample observation. The F statistic is used to test the significance of each regression equation.The relationship between withdrawn CSF volume and ICP was analyzed with a parabolic regression model to determine the P-V curve as previously documented. The para” was detected in IICP patients, a brain CT scan was arranged again to evaluate if any changes in intracranial condition had occurred. The indicator “a” was compared at different levels of initial ICP and in different intracranial conditions. The overall brain CT scans in 20 patients were reviewed and analyzed. In the group with hydrocephalus, patients presented with prolonged intracranial hypertension and the last brain CT scans revealed a dilated ventricle with minimal residual primary mass lesion or brain edema. The P-V curves obtained from the condition of hydrocephalus with minimal intracranial mass effect were gathered in Group A. On the other hand, the brain CT sometimes showed severe primary intracranial mass lesion with perifocal edema, brain swelling, and a slender ventricle. The P-V curves obtained from this situation were gathered into Group B. There were still several other intracranial conditions without significant intracranial mass lesion or severe hydrocephalus. There were scattered intracerebral hemorrhage, subarachnoid hemorrhage, mild brain swelling or thin subdural hemorrhage. The P-V curves from other intracranial conditions not including hydrocephalus in Group A or severe intracranial mass lesion in Group B were gathered into Group C. The mean of indictor “a” in each group was calculated and Levene’s test was used to assess the equality of variances in different samples. The Kruskal-Wallis one-way analysis of variance  was used to test whether the mean of indicator “a” has significant differences for the diverse intracranial conditions in Group A, B, and C. For multiple comparison, the Mann-Whitney U test with Bonferroni correction and Dunn test were used. Differences of p < 0.05 were considered statistically significant. For statistical analysis, we used the software statistical package for the social sciences version 17.0 for windows  and Microsoft Excel 2007.Another brain CT would be performed if a persistent IICP condition was observed even after CSF drainage, or if neurological deficits or a significant deterioration in GCS were found. Additionally, if a rapid change of indicator “p < 0.005) with the F statistic . The plot of the 139 values of indicator “a” in the parabolic regression equations against the initial ICP is shown in y = 0.024x-0.145 (R2 = 0.156). Linear regression analysis of indicator “a” versus the initial ICP in all P-V curves yielded low coefficients of correlation.There were 20 patients: 14 males and 6 females, with an age range of 50 ± 16 (mean ± SD) years old included in this study. There were seven patients with an initial diagnosis of spontaneous ICH. Nine patients had traumatic brain injury. Four patients had spontaneous SAH with or without hydrocephalus . A serietatistic . The ovea” in this group was 0.173± 0.024 (95% CI) [a” was 0.663± 0.062 (95% CI). The other 51 episodes of CSF drainage were gathered from Group C and the mean for indicator “a” was 0.392 ± 0.071 (95% CI) [a” in Group A, B and C compared using the Kruskal- Wallis test showed significant differences between the three groups (p < 0.001)  [a” were always obtained in patients with prolonged intracranial hypertension and hydrocephalus without significant intracranial mass effect in the brain CT scan. On the other hand, the mean for indicator “a” in Group B was significantly higher than the other groups (p < 0.001) [a” was always observed. The mean for indicator “a” from other conditions, not including severe intracranial mass effect or hydrocephalus only, in Group C was similar to the mean of overall samples.There were 40 episodes of CSF drainage in Group A and the mean for indicator “(95% CI) . Another(95% CI) . The equ< 0.001) . The sma< 0.001) . In the a” within one day or two successive days after EVD surgery  presented with enlarged primary ICH with perifocal edema, brain swelling and slender ventricles during follow-up brain CT scans. They all received medical treatment and CSF drainage because there was no accessible lesion for surgical decompression and they survived brain injury. A delayed contusion hemorrhage that needed surgical decompression was detected in one patient (patient 3) due to a rapid elevation of indicator “a” from 0.32 to 0.755 without change in GCS scores. Afterwards, he underwent right side craniotomy for delayed hemorrhage. Two of the 7 patients (patient 5 and 7) died due to the progression of primary brain lesion or new onset intracranial pathology. Patient 5 suffered from a left putaminal hemorrhage and underwent right frontal EVD only. Rapid elevation of the indicator “a” was observed on post-operative day (POD) 6 and the follow-up image revealed left ICH progression with brainstem compression. The patient only received conservative treatment and died on POD 15. Patient 7 suffered a left internal carotid artery (ICA) traumatic pseudoaneurysm and diffuse SAH in a traffic accident. Left ICA and right anterior cerebral artery (ACA) territory infarction, severe brain swelling and diffuse vasospasm occurred on POD 4 with the rapid elevation of indicator “a” to 0.501 and expired on POD 9. Compared with the GOS after 6 months, the outcome in the 7 patients with rapid elevation was relatively poor amongst the 20 patients. There were 2 patients who died, a GOS of 2 in 3 patients, a GOS of 4 in 1 patient and a GOS of 5 in 1 patient. On the other hand, no patients died among the other 13 patients. The GOS outcomes after 6 months were a GOS of 2 in 3 patients, a GOS of 3 in 2 patients, a GOS of 4 in 3 patients and a GOS of 5 in 5 patients.When the outcome was reviewed after 6 months, there were 6 patients with a GCS of 3–8, 4 patients with a GCS of 9–12 and 8 patients with a GCS of 13–15. From our results, 7 of 20 patients (35%) were observed with a rapid elevation of indicator “ surgery . Brain Ca” is shown in a” with parabolic regression in P-V curve declined from 0.688 on POD 1 to 0.272 on POD 4 [a” began to increase after POD 4 and reached the highest point (0.76) on POD 6. The patient’s GCS scores remained E1VeM4 during these periods. A brain CT was performed on POD 6 and revealed that the left thalamic hemorrhage was stationary and the ventricle size decreased. The brain parenchyma was tight, especially on the left side, and severe perifocal edema was shown [a” began to decline again after POD 6 and it was 0.283 on POD 9 [A 48-year-old male patient who had hypertension and hypertrophic cardiomyopathy presented with an acute onset of consciousness change. His GCS was E1V1M4 on arrival in our emergency room (ER). The emergent brain CT revealed left thalamic hemorrhage, intraventricular hemorrhage (IVH) and hydrocephalus . Bilateron POD 4 . Howeveras shown . The indon POD 9 . The folon POD 9 . A VP sha” declined gradually from 0.417 on POD 1 to 0.141 on POD 5 [a”. The progression of the P-V curves from POD1 to POD5 in case 2 is shown in A 31-year-old male patient had history of thalamic and brainstem arteriovenous malformation and he underwent stereotactic radiosurgery and right VP shunt 4 years ago. He presented with a progressive headache for 4 days. He was drowsy and experienced general malaise with left side limb weakness noted when he arrived in our emergency room. The brain CT revealed IVH and bilateral dilated ventricles . The rigon POD 5  and he won POD 5 , therefoa”, from 0.32 to 0.755, was noted on POD 1 without changes in GCS scores [a” declined to 0.375 and it fluctuated between 0.234 and 0.42 during the first week [A 65-year-old male patient suffered from a head injury during a traffic accident. He was found with a change in consciousness immediately after the injury and his GCS was E1V1M5 on arrival in our ER. The initial brain CT revealed left fronto-temporal (F-T) epidural hematoma (EDH) and bilateral fontal and temporal small contusion hemorrhage, and SAH . He undeS scores . The folS scores . He underst week . He had ICP monitoring is a common neurosurgical practice for patients with intracranial pathology. ICP values are used as a measure of pathology, as an indicator for treatment response, and to monitor cerebral perfusion. The upper limit of normal ICP in adults is usually considered to be 15 mm Hg, although the usual range is 5 to 10 mm Hg. ICP can be measured using intraventricular, intraparenchymal, subdural, or epidural devices. Ventriculostomy remains the gold standard for monitoring ICP because of its accuracy and ease of calibration. Access to CSF for dynamic testing and drainage to control ICP are additional benefits. There is no uniform agreement about the critical level of ICP beyond which treatment is mandatory. Saul andComprehending the intracranial V-P relationship in patients with increased ICP can help us decide on a treatment plan and predict the prognosis. Miller and Garibi documented the concept of volume pressure response (VPR). A volumetric change in patients of 1 ml CSF in one second was used and the resultant immediate change in ICP was termed the VPR. It is expressed in mm Hg/ml and is used as an index of intracranial elastance. The VPR et al. concluded that the VPR does not provide reliable information about the V-P relationship because the correlation coefficient calculated from regression analysis of VPR and PVI was as low as -0.33.[Marmarou documented that the plotting of ICP logarithmically against volume produces a straight line. Its slope is the pressure-volume index (PVI), or the calculated volume in milliliters needed to raise ICP by a factor of 10. PVI is considered a parameter that expresses intracranial compliance., 3, 7 Itas -0.33. The PVI as -0.33. There iset al., documented the clinical practice of continuous monitoring of intracranial compliance for patients with closed severe traumatic brain injury.[A single intracranial compliance (ICC) of a patient at one time cannot reflect the dynamic intracranial conditions. Kiening, n injury. Pathologn injury.a” as an indicator, and it can display the dynamic changes in intracranial V-P relationship and is comparable in different conditions. Most importantly, Miller has documented that the P-V curves change in patients based on different conditions. In his report, mannitol and steroids reduce the VPR much more than they reduce ICP itself. It was suggested that these agents alter the shape of the P-V curve, flattening it and creating a situation in which the brain is much more tolerant to the addition of volume.[a” representing diverse intracranial conditions. The change of indicator “a” indicates a change in the P-V curve and may represent the deterioration or regression of an intracranial lesion. A series of P-V curves can provide an easier way to realize the intracranial V-P relationship and the course of brain injury. In one patient with a status of increased ICP, as the indicator “a” in the parabolic P-V curve decreased, the P-V curve became more flat [a” in the P-V curve represents better compliance of the brain with better spatial compensation ability.Although VPR, PVI, and ICC were documented to increase understanding of the intracranial V-P relationship, no reports can explain how to correlate them with the dynamic intracranial conditions immediately. VPR, PVI, and ICC are not as widely applied in current clinical practice as ICP monitors are nowadays. The V-P relationships can be depicted by graphing the successive response of ICP to volume added or withdrawn from the ventricle., 14, 15 f volume. Differenore flat . In clina” because the linear regression analysis of indicator “a” versus the initial ICP yielded low coefficients of correlation (R2 = 0.156) [a” were obtained from patients with less elevated ICP status with an ICP < 20 mm Hg. Even patients with greater IICP status (ICP > 25 mmHg) could yield a smaller indicator “a” that was below the linear regression line [a” may be a clue or sign of poor intracranial spatial compensation ability. From our results, the patients in Group B significantly had the highest value of indicator “a” when compared to the other conditions (p < 0.001). In patients with IICP that have a similar clinical conditions and the same GCS scores, a larger indicator “a” is usually detected in patients with severe intracranial parenchymal pathology and mass effect such as case illustration 1 [Figs a” is usually observed in patients with relatively benign intracranial conditions. The mean of indicator “a” in Group A was smallest with statistical significance (p < 0.001). If patients showed prolonged IICP status with a need for persistent CSF drainage and a smaller indicator “a”, the brain CT usually revealed hydrocephalus alone such as case illustration 2 [Figs a” [a” reveals significant difference between the two extreme intracranial conditions in Group A and B [a” was noted in patients with IICP, hydrocephalus should be considered and a VP shunt is usually indicated. In this study, 12 patients (60%) had prolonged intracranial hypertension and hydrocephalus and they all underwent VP shunt within one month after primary brain injury. If a higher indicator “a” was observed, intracranial mass lesion with brain swelling was usually the main cause of intracranial hypertension. Surgical decompression should be considered according to the brain CT findings.No direct relationship can be defined between the level of ICP and the neurological status of patients at that time or the subsequent clinical course. Increased ICP level does not provide reliable correlation to the indicator “= 0.156) . From ouion line . In dailn 1 Figs  and 3. An 2 Figs  and 5. Tn 2 Figs  with a s[Figs a” . Through A and B . If a pea” in one patient can reflect the dynamic changes of intracranial V-P relationship and corresponding intracranial pathology, allowing ongoing intracranial deterioration to be detected earlier in IICP patients with the same GCS scores. In case illustration 1, the highest indicator “a” was detected on POD 6 with the same GCS scores as POD 1. However, the brain CT at that time revealed progression of ICH and cerebral edema with significant mass effect [Figs a” during one or two successive days after EVD surgery [a” presented no obvious enlargement in primary ICH, the progression of peri-hematoma edema and whole brain swelling with slender ventricles was observed. Patient 8 developed a new intracranial pathology with left ICA and right ACA territory infarction along with a rapidly elevated indicator “a”. The indicator “a” in two mortality cases  can also be assessed and adjusted to protect against secondary brain injury.Take a glance at our results; the data for indicator “ard Figs . The absa” can reflect the status of the P-V curve and the dynamic change of the intracranial V-P relationship and is comparable at different times. A series of P-V curves can offer information about the changes in intracranial conditions and the course of brain injury. The increased ICP level does not provide reliable correlation with the indicator “a”. In clinical practice, a smaller indicator “a” of the P-V curve represents better compliance of the brain with better spatial compensation ability. A significantly higher indicator “a” is always observed in patients with severe intracranial mass lesion with cerebral edema and slender ventricles. On the other hand, a significantly smaller indicator “a” is always observed in patients with relatively benign intracranial lesions such as hydrocephalus alone. Even in patients presenting similar intracranial hypertension and same GCS scores, a rapid elevation of the indicator “a” is usually observed along with intracranial condition deterioration. Brain CT scans should be performed early if a rapid elevation of indicator “a” is detected in IICP patients even with the same GCS scores as it can reveal some ongoing intracranial pathology before the visible deterioration of clinical conditions. Some surgical decompression procedures can also be performed early if the indicator “a” indicates the need. An absolute value of indicator “a” that represents a good or bad intracranial compliance needs to be further investigated. The volume pressure indicator “a” could offer a more effective, meaningful, and safe method in clinical observation for neurosurgical critical care. A larger study with more patients and different intracranial conditions needs to be performed in the future to strengthen the value of the volume pressure indicator “a” for clinical application.The parabolic regression model is a reliable mathematic model to acquire a segment of the P-V curve in patients with increased ICP. The single indicator “


It was demonstrated that thermal sensing could be based on three temperature dependent luminescence parameters: the luminescence intensity ratio, the spectral line position and the line bandwidth. Advantages and limitations of each sensing parameter as well as thermal sensitivity and thermal uncertainty were calculated and discussed. The influence of Nd3+ doping concentration on the sensitivity of luminescent thermometers was also studied.We report on the potential application of NIR–to–NIR Nd Last decade the biomedical field becomes the research area in which the nanothermometers have found high impact and applicability since the sizes of the nanoparticles are similar to those of the majority of biological objects . Successful application in this area imposes additional requirements on nanothermometers: they have to combine an operation within physiological temperature range (295−320 K)1 with biocompatibility and noninvasiveness, and working in moving biological fluids5. Along with biomedicine, nanothermometers can be used in various industrial applications: for example, in photonic, electronic and optoelectronic devices and circuits, that are being continuously miniaturized, and whose temperature strongly affects their performance. It should be noted, that industry application usually requires wider temperature intervals than aforementioned physiological range8.Measuring temperature at micro- and nanoscale is an important task in science, technology and medicine9. Fluorescence sensors should be materials that upon optical excitation emit light and their temperature dependence can be calibrated using the changes of one or more measurable parameters, such as the emission intensity, bandwidth, spectral position, polarization or lifetime of the emitting level10. Various luminescent materials such as organic dyes12, polymer nanoprobes14, layered double hydroxides16, quantum dots18, and rare earth doped inorganic nanoparticles22 have been proposed as nanothermometers. Unique spectral features  together with good chemical and physical stability make rare earth doped inorganic nanoparticles one of the most promising candidates for thermal sensing in wide temperature range through fluorescence thermometry.Among the diverse approaches to thermal sensing at micro- and nanoscale, fluorescence nanothermometry has attracted significant attention due to noninvasive, contactless, and easy to use, unlike conventional tools, such as thermocouple and fiber optic probes or volumetric methods 3+, Gd3+, Dy3+, Ho3+, Er3+, Tm3+ or Eu3+ are based on luminescence intensity ratio, whereas only a few scientific papers are devoted to the thermometers based on other temperature dependent luminescence parameter. Therefore, it is very important to carry out a systematic study of advantages and limitations of various thermal sensing luminescence parameters.Up to now, the great number of rare earth doped phosphors has been successfully demonstrated as efficient thermometers especially in the biological temperature range. Majority of down- and up-converting fluorescence thermometers doped with Nd4:Nd3+ phosphors: the luminescence intensity ratio, the spectral line position and the line bandwidth. It was found that aforementioned luminescence temperature dependent parameters can provide thermal sensing in wide range (123–873 K), which is sufficient for majority of industry application. The influence of doping concentration and sensing parameter on thermal sensitivity was studied and discussed in detail. The temperature uncertainties of YVO4:Nd3+ 2.4 at.% nanothermometer based on different sensing parameter were calculated and compared.Here, thermal sensing was based on monitoring three different temperature dependent parameters of NIR-to-NIR YVO4:Nd3+ nanoparticles (NPs) have been studied in our previous paper23. It was found that all samples of concentration series have single tetragonal phase without impurities. Mean size of nanoparticles (68 nm) obtained using static light scattering technique matches well with average size (60–70 nm) observed using scanning electron microscopy.Phase composition and size of synthesized YVO4:Nd3+ NPs. It was found that Nd3+ ions in YVO4 host have quite broad excitation bandwidths (14 nm), therefore they are practically unaffected by small changes in the excitation wavelength 20. Cost effective 808 nm diodes also have an advantage compared with 790 nm ones often used for other Nd3+ doped NPs from the biological point of view25.Commercial 808 nm laser diode can effectively excite emission of YVO2. One of the most widespread methods is ratiometric approach in which thermal reading is achieved by comparing the relative intensity between different spectral lines. Luminescence intensity ratio (LIR) prevents errors in measurements arising from power fluctuations of the excitation source, variations on the concentration of luminescent nanoparticles, and inhomogeneities of the material26. LIR technique constitutes a self-referencing method to compute the absolute temperature, since one spectrum contains all of the information needed, avoiding the use of an internal reference1.All luminescence nanothermometers can be divided into different groups based on the particular parameter of luminescence which is analyzed, and from which parameter the thermal reading is ultimately extracted. Emission intensity, spectral line position, bandwidth, lifetime, and polarization could be used to determine local temperature3+-doped materials for thermal sensing in the biological temperature range29. LIR was obtained using emission lines lying in the first, second and third biological windows33. Recently, we demonstrated that thermal sensitivity of nanothermometers could be significantly enhanced by calculation of LIR between emission line (1063.9 nm) and valley (1065.3 nm)34. However, quite small energy separation between wavelengths used for LIR calculation limits possible temperature range for sensing. Here, we have defined LIR technique temperature limits for YVO4:Nd3+ NPs emitting in the second biological window. Figure 4:Nd3+ 2.4 at.% NPs obtained at different temperatures . It should be noted that considered temperature region is much broader than usually studied physiological range. As can be seen from Fig. 4F3/2(1) − 4I11/2(1)) and 1071.1 nm (4F3/2(2) − 4I11/2(3)) due to the significant broadening of spectral lines at high temperatures.Nowadays, there are a lot of papers demonstrated successful application of LIR technique in Nd4:Nd3+ NPs emitting in the second biological window based on LIR technique is 123–398 K.Temperature induced change of LIR is explained by modification of energy levels population according to the Boltzmann formula:equation . However36. Thermal shifts to the blue can be caused by thermal expansion of the crystal lattice due to the changes of crystalline-field strength and impurity-level energies. Such shifts were observed for some transitions of Nd3+ in the soft hydrated crystal Pr(NO3)3·6H2O. However, it was found that thermal expansion is negligible in hard ionic crystals36.In order to broaden the temperature range, other spectroscopic parameters were suggested for thermal sensing. It was found that increase of temperature leads to the red shift of some emission line positions. When the crystal temperature is increased, energy levels and, therefore, spectral lines broaden, invariably as the higher phonon modes are occupied. Since there are many high-lying energy levels which couples, an energy level is normally lowered. Further, it is usually the case that the temperature dependence of higher levels is larger than for lower levels because of smaller energy denominators. As a result, the spectral lines are observed to shift normally to the longer wavelengths when the temperature is increased37. According to the phonon theory39, the line position is affected by the crystal strain inhomogeneity, direct one-phonon processes, multiphonon processes, and Raman phonon scattering processes. As was found in earlier studies40, thermal shift is mainly governed by electron–host interaction effect associated with Raman scattering, and therefore the simplified theoretical expressions for the line shift can be written in the following form41:0, α, ΘD represent the initial line position , the electron–host coupling parameter, and the effective Debye temperature, respectively. We monitored position of the most intensive emission band of YVO4:Nd3+ 2.4 at % NPs, which is attributed to the transition between the Stark levels of the 4F3/2 and 4I11/2 states  − 4I11/2 (Y1) transition is shown in Fig. So, shifting of the emission line is usually associated with the electron–phonon coupling effect, which results from the fact that at higher temperatures host vibration modes introduce random perturbation of the ion’s local environmenttes Fig. . Spectra2: 0.99882 and 0.99872 for equation  − 4I11/2 (Y1) transition  perfectly fits this requirement  − 4I9/2 (Z5) and 4F3/2 (R1) − 4I9/2 (Z5) transitions which can be resolved only at very low temperatures (T ~ 10 K)42. It was found that the observed emission line can be well approximated by a Voigt profile in the considered temperature range (123–873 K). The temperature dependence of the full width at half maximum (FWHM) of the emission band is shown in Fig. In our case the monitored band is attributed to the most intensive ion Fig. . The linion Fig.  with preent Fig. . Actuall26:37.One of the most important parameter for characterizing luminescent thermometers is the relative thermal sensitivity, which is defined as followsThe relative thermal sensitivity of all temperature dependent parameters was obtained at T = 303 K (or at T = 298 K in case of FWHM). Example of the relative thermal sensitivity calculation based on LIR is presented below:−1] at T = 303 K and at T = 0 K, unlike the spectral line position at considered temperature as was shown by Ł. Marciniak et al.37.Calculation of the relative thermal sensitivity based on other parameters is presented in Supporting Information. It should be emphasized that in case when temperature dependent parameter is the spectral line position, Λ value should be a spectral shift between emission line [in cm3+ concentration. Here, YVO4:Nd3+ concentration series consisting of 0.6, 2.4 and 4.8 at.% doped samples were studied. All of the calculated thermal sensitivities for YVO4:Nd3+ NPs based on the different types of luminescent parameters are listed in Table Since all three parameters were found to be temperature dependent, each of them was examined as a function of the Nd−1 for YVO4:Nd3+ 2.4 at.%, while the lowest was found for FWHM based luminescent thermometers. It should be noted that the thermal sensitivity did not demonstrate monotonical dependence on Nd3+ doping concentration: the best performance was achieved for 2.4 at.% doped sample for all sensing techniques. The perspective candidate for a non-contact temperature sensor should possess not only the high thermal sensitivity but also the simplicity of the readout. It is important to note that accurate determination of line position or FWHM are quite difficult in real experiments due to the necessity of providing high resolution detection systems. Our LIR based YVO4:Nd3+ thermometers had higher sensitivities (0.47–0.54% K−1) than other single Nd-doped materials. Despite the high thermal sensitivity and readout simplicity, it is worthy to note that LIR technique can be used only in the limited temperature range: 123–398 K. Thus, non-contact luminescence thermal sensor for higher temperature region should be based on line position or FWHM.The highest thermal sensitivity was found for line position method reaching up to 0.75% K46. This parameter defines the accuracy of temperature evaluation using nanothermometers and should be as small as possible. The minimum temperature uncertainty can be found with several methods performed and compared in our previous paper34. Here, 50 consecutive emission spectra of YVO4:Nd3+ 2.4 at.% NPs with fixed heating stage temperature (313 K) were measured. Then, the temperature corresponding to each spectrum was calculated using calibration curves based on various thermal sensing parameters: LIR, line position and FWHM. The obtained temperature distribution was fitted by Gauss function for each sensing parameter, and standard deviation was used as an estimation of the thermal resolution that can be achieved in a measurement with chosen method 4:Nd3+ NPs synthesized with modified Pechini method were successfully used as nanothermometers operating in the first and second biological windows. Luminescence thermal sensing was based on monitoring three different temperature dependent parameters: LIR, line position and FWHM. The highest thermal sensitivity was found for line position method reaching up to 0.75% K−1, whereas FWHM method demonstrated the lowest values. Despite high thermal sensitivity and readout simplicity, LIR technique can be used only in the limited temperature range (123–398 K) due to temperature-induced line broadening and shifting. Theoretical expressions and simplified functions were used to fit temperature behavior of both line position and FWHM. It was demonstrated that aforementioned luminescence temperature dependent parameters can provide thermal sensing in wide range (123–873 K), which is sufficient for majority of industry application. Doping concentration affects thermal sensitivity of LIR, line position and FWHM techniques similarly: the best values were obtained for sample with the highest luminescence intensity − YVO4:Nd3+ 2.4 at.%. The minimum temperature uncertainty (ΔT = 0.1 K) was obtained for LIR technique.YVO4:Nd3+ nanoparticles used in this work were synthesized using a previously reported modified Pechini method47. Fluorescence characterization was performed by using T64000 Raman Spectrometer. The Nd3+-doped YVO4 NPs were optically excited with a 808 nm single mode laser Coherent MBR-110 operating in CW mode. The laser beam was focused into the sample by using a 4x long working distance microscope objective (NA 0.1). The fluorescence was collected by using the same microscope objective and was spectrally analyzed by single spectrometer and liquid nitrogen cooled Symphony II and Peltier cooled Synapse CCD detectors. The temperature was controlled with a heating stage Linkam (Linkam THMS 600 of 0.1 °C temperature stability and 0.1 °C set point resolution).YVOSUPPLEMENTARY INFO


Recordings of magnetic fields, thought to be crucial to our solar system’s rapid accretion, are potentially retained in unaltered nanometric low-Ni kamacite  grains encased within dusty olivine crystals, found in the chondrules of unequilibrated chondrites. However, most of these kamacite grains are magnetically non-uniform, so their ability to retain four-billion-year-old magnetic recordings cannot be estimated by previous theories, which assume only uniform magnetization. Here, we demonstrate that non-uniformly magnetized nanometric kamacite grains are stable over solar system timescales and likely the primary carrier of remanence in dusty olivine. By performing in-situ temperature-dependent nanometric magnetic measurements using off-axis electron holography, we demonstrate the thermal stability of multi-vortex kamacite grains from the chondritic Bishunpur meteorite. Combined with numerical micromagnetic modeling, we determine the stability of the magnetization of these grains. Our study shows that dusty olivine kamacite grains are capable of retaining magnetic recordings from the accreting solar system. Magnetic fields are thought to have been influential in the formation of our solar system. Here, the authors observe thermomagnetically stable, non-uniformly magnetized kamacite grains within chondritic meteorites, and calculate the grains to retain recordings of these magnetic fields. A recent estimate of the ancient magnetic field intensity  from dusty olivine in Semarkona3 has provided an upper bound of 54 ± 21 μT for the magnetic field present in the chondrule-forming region ) of the protoplanetary disk during its first two to three million years5. This estimate is widely used in models for chondrule formation7 and for the accretionary dynamics of the protoplanetary disk9.Unaltered meteorites originating from our own protoplanetary disk acquired a thermoremanent magnetization (TRM) during formation and present an excellent opportunity to understand the extent of the early solar system magnetic field. The most likely material to have retained this field information is dusty olivine: assemblages of nanometric low-Ni kamacite grains protected from alteration by their host olivine crystal, found in the chondrules of unequilibrated primitive chondrites11. Retention of magnetic remanence over geological timescales, which is the underpinning hypothesis that enables paleomagnetism, is only predicted for uniformly magnetized grains by Néel’s single domain (SD) theory12. Non-uniformly magnetized grains such as magnetic vortex states are not described by Néel’s SD theory. Despite efforts to understand magnetic vortex states14, it is unknown whether non-uniformly magnetized kamacite grains can retain their TRM for solar system timescales, i.e., 4.6 Ga. It is therefore of great importance to establish which magnetization states occur in the natural remanence carriers, and whether these non-uniform magnetization states can retain a magnetic remanence imparted by magnetic fields that were present in the protoplanetary disk billions of years ago15.The magnetization carriers in dusty olivine are dominantly kamacite grains that have sizes greater than 25 nm and support non-uniform vortex magnetization states16 (nanometric magnetic imaging) and numerical micromagnetic modeling17 to determine whether dusty olivine can retain a record of the magnetic field from the early solar system.Here we study chondrules from the unequilibrated ordinary chondrite Bishunpur (LL3.1) using the advanced transmission electron microscope (TEM) technique of in-situ temperature-dependent off-axis electron holography11.We recorded room-temperature magnetic induction maps from 19 kamacite grains Fig. . The aveWe recorded in-situ temperature-dependent holographic magnetic induction maps (see Methods) of four kamacite grains and present the heating sequence for one of them in Fig. 17  to model the three-dimensional magnetization states compatible with the grain’s shape and mineralogy. We found that the grain was in a multi-vortex state with its magnetization aligned with the long axis   micromagnetic algorithmis) Fig. . Using a22 to calculate the thermal relaxation times as a function of size and AR for Fe cubes and cuboids. Initially, we found local-energy minimum (LEM) magnetization states for the Fe cubes and cuboids by performing 100 energy minimizations for randomized magnetization directions for each morphology  have ARs of ~ 1.5. At such elongations for all grain sizes modeled (10–50 nm) the magnetizations are stable for timescales greater than the age of the solar system, independent of their uniform or non-uniform states 00 °C21. 27. Our observations and calculations show that SV or multi-vortex magnetization state Fe grains in dusty olivine will carry magnetic remanence originating from the early solar system. Most current paleointensity protocols implicitly assume that the magnetization carriers behave like uniform SD magnetization states, as the protocols are based on Néel’s theory of SD grains12. Non-uniform magnetization states are the most abundant state of magnetization present in rocks and meteorites, however their thermal and temporal stabilities are poorly understood and they have previously been considered to be poor magnetic recorders. This study presents a step change in our understanding of non-uniform magnetic states. It is now clear that a more comprehensive understanding of the thermomagnetic characteristics of magnetic vortex states will facilitate more sophisticated and sample-specific paleointensity estimates, which will further our understanding of how the protoplanetary disk evolved into our present-day planetary system.Paleomagnetic data are some of the only sources of evidence of early solar system conditions that constrain mechanisms of heating and momentum transport in the protoplanetary diskSamples for the advanced TEM technique of off-axis electron holography (hereafter holography) were prepared using FIB milling from a polished section of the Bishunpur meteorite and either attached to a Cu Omniprobe grid for room temperature analysis or placed on the windows of a silicon nitride EMheaterchip for in-situ heating in a DENSSolutions double tilt TEM specimen holder. FIB milling, (S)TEM imaging, chemical analysis, and holography experiments were conducted at the Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Germany.28.Electron holograms were acquired using an FEI Titan 80–300 TEM operated in Lorentz mode at 300 kV using a charge-coupled device camera and an electron biprism typically at 50 V. Magnetic induction maps were recorded after tilting the sample to ± 70° and applying a vertical magnetic field of > 1.5 T using the conventional microscope objective lens, in order to acquire images before and after reversing the direction of magnetization in the sample. Evaluation of half of the difference between phase images recorded with opposite magnetization directions in the sample was used to remove the mean inner potential contribution to the phase. The mean inner potential was subtracted from the unwrapped total phase shift in order to construct magnetic induction maps that were representative of the magnetic remanence−1 and each temperature interval was maintained for 10 min, to allow sufficient time for imaging. The mean inner potential was subtracted from the unwrapped total phase shift acquired at each temperature interval, to allow the construction of magnetic induction maps representative of the magnetic remanence, as shown previously29.In order to determine the change in magnetic induction during heating, the sample was magnetized and images were recorded at room temperature, at 100 °C, and then at temperatures up to 800 °C in 100 °C intervals. The same procedure was followed during cooling. The ramp during heating was 50 °C min25. We determined the magnetization states associated with different grain sizes of Fe using FEM micromagnetic simulations17. Tetrahedral meshes were generated for this using MRshRRILL and FEM models were performed using MERRILL17. The magnetic free energy was determined for each of the tetrahedra and summed over all tetrahedra to determine Etot, which the FEM discretized for the minimization of an initial state, m, where the magnetization at each node of each element was given a random direction for the grain in question, Ω, according to the expressionA, the exchange constant; K1, the magnetocrystalline anisotropy; and Ms, the saturation magnetization. Hz and Hd are external and self-demagnetizing fields, respectively. The material parameter constants used for room temperature Fe25: A = 2 × 10−11 Jm−1, K1 = 4.8 × 104 Jm−3, and Ms = 1.72 × 106 Am−1. The material parameter constants used for Fe at 300 °C: A = 1.52 × 10−11 Jm−1, K1 = 2.2 × 104 Jm−3, and Ms = 1.61 × 106 Am−1.Magnetic domain stability is highly grain-size-dependent. At very small grain sizes, uniform magnetization is typically unstable due to thermal fluctuations. As the grain size increases, a non-uniform magnetization state becomes the most energetically favorable stateEtot using a modified conjugate gradient method18. For each grain geometry and size for which the relaxation time was evaluated, 100 minimizations were performed to calculate the most favorable LEM states. Two different magnetization states, L1 and L2, with lowest energy were then selected as the start and end configurations of an initial path of 100 magnetization states transforming L1 into L2. MERRILL’s combined NEB and action minimization method was used to determine the nearest minimum-action path connecting L1 and L2, which also defines the corresponding thermal energy barrier18. For non-uniform vortex states, L1 and L2 were required to have the same helical sense of vortex core rotation (helicity), as unwinding of the core requires much more energy than retaining the same helicity. Helicity was determined by calculating m · (∇ × m), where m is the magnetization vector. The relaxation time (τ) is related to the energy barrier (ΔE) by the Néel–Arrhenius equation12C is the atomic switching frequency (10−9 s), kB is Boltzmann’s constant, T is the temperature in Kelvin, and ΔE = ES − E(L1) is the energy difference between the highest saddle point and the LEM L1 determined by the NEB method. The relaxation time directly determines whether dusty olivine can theoretically retain its magnetization over solar system timescales.LEM magnetization states are found by minimizing The data that support the findings of this study are available from the corresponding author upon request.Supplementary Information(PDF 11138 kb)Peer Review File(PDF 292 kb)Description of Additional Supplementary Files(PDF 171 kb)Supplementary Movie 1