Although strain and crystal damage induce strong PL quenching, the initial balance between radiative and nonradiative processes in the microcrystals is restored within a few minutes. The stepwise quenching–recovery cycles induced by the mechanical action is interpreted as a modulation of the PL blinking behavior. This study proposes that the dynamic equilibrium between active and inactive states of the metastable nonradiative recombination centers causing blinking is perturbed by strain. Reversible stochastic transformation of several nonradiative centers per microcrystal under application/release of the local stress can lead to the observed PL quenching and recovery. Fitting the experimental PL trajectories by a phenomenological model based on viscoelasticity provides a characteristic time of strain relaxation in MAPbI3 on the order of 10–100 s. The key role of metastable defect states in nonradiative losses and in the self‐healing properties of perovskites is suggested.The photoluminescence (PL) of metal halide perovskites can recover after light or current‐induced degradation. This self‐healing ability is tested by acting mechanically on MAPbI Defects created in perovskite crystals by a local mechanical force are temporary. After several minutes they disappear leading to recovery of the initially quenched photoluminescence. The process is explained by treating the perovskite as a viscoelastic solid and relating nonradiative charge recombination to strain. The authors argue that the strain affects photoluminescence via stabilizing metastable super traps also thought to be responsible for photoluminescence blinking. One of the main features making perovskites so successful is the tolerance of their optoelectronic properties to chemical and structural defects inevitably formed during fast crystallization in solution and by kinetic competition between several intermediates. In addition to defect tolerance, MHPs were found to possess some features which can be loosely formulated as self‐healing properties. It means that a partly degraded device  can restore its performance after several hours at “rest.” The most common demonstrations of self‐healing processes are recovery of photoluminescence (PL) from bleaching, light‐induced PL enhancement, and improvement of electronic properties of thin films after prolonged storage. The combination of defect tolerance and the ability to heal spontaneously or under an external influence  are the crucial features opening the door for perovskites to develop into long lasting or “eternal” devices.Metal halide perovskites (MHPs) are semiconductors prepared by room‐temperature crystallization from precursor solutions.2, 3 Self‐healing not only concerns defects and structures at the nanoscale, but also the repair of macroscopic cracks and even reconstruction of broken single crystals. The repair of broken mm‐sized single crystals requires the crystal fragments to be kept together for 24 h under pressures of around 1 MPa, while only a minute is needed to heal microcracks when the parts of a cracked film are pressed against each other. All these properties make MHPs, on the one hand, not very stable, on the other hand, they allow the materials and devices to recover their performance after degradation.The feature of MHPs making self‐healing possible is the soft and dynamic ionic crystal lattice. It allows for ion migration and dynamic formation and annihilation of defect states. It is also very important that the formation energy for many defect states is higher than the energy needed to simply rebuilt the perovskite unit cell and avoid defect formation.18 Sel Recently, photoassisted PL recovery after bleaching was also observed in monolayer transition metal dichalcogenide (1L‐WS2) materials.Although these effects are very prominent in MHPs, these materials are not unique in this context. For example, transient phenomena as reversible PL bleaching/enhancement under light soaking have been observed quite some time ago, for example for films of CdSe and CIGS materials and also have been related to defect metastability.22 Rec When comparing classical semiconductor quantum dots with MHPs we note that PL blinking and flickering is not only observed in MHP nanocrystals, but also in sub‐micrometer crystals, grains in thin films and even in micrometer‐sized objects. The current understanding is that the PL intensity fluctuations occur due to the presence of very efficient, yet metastable nonradiative (NR) recombination centers, also called supertraps  appears as a valuable tool to influence electronic properties of soft MHP materials by mechanical nanomanipulation. Indeed, the tip of an AFM cantilever can be used not only to probe the sample topography, but also to apply mechanical stress, to pull, stretch, and break organic molecules,56 and3NH3PbI3  polycrystalline perovskite microcrystals. The AFM tip was used not only to apply a localized anisotropic force, but also to scratch and even cut MAPbI3 crystals at the nanoscale. Despite such vigorous mechanical disturbances, we did not observe permanent quenching of the PL from the crystals. Initial complete PL quenching caused by the mechanical manipulation, was found to always disappear after several minutes leading to full recovery of the initial PL intensity. We show a clear connection between the tip‐induced quenching and PL blinking behavior, discuss possible physical mechanisms of self‐healing based on metastable NR‐ recombination centers and propose a phenomenological model of the effect based on viscoelasticity.In this work, we combined AFM and confocal PL microscopy to study CH2m MAPbI3 precursor solution was prepared by mixing 461 mg PbI2 (99% from Sigma‐Aldrich) and 159 mg MAI (99% from Sigma‐Aldrich) in 1.25 mL γ‐butyrolactone . The solution was stirred for 2 h at 60 °C. To prepare MAPbI3 microcrystals, the MAPbI3‐GBL precursor solution was diluted 1:2000 (concentration of 4 × 10−4 m). 20 µL of this solution were drop‐cast on a glass substrate. Finally, the sample was annealed at 80 °C for 20 min by placing the glass substrate on a temperature‐controlled heating plate. All preparations were carried out in ambient air. This method usually leads to polycrystalline perovskite particles of various size from tens of nanometers to tens of micrometers dispersed on the glass surface.A 0.8 Figure mfp‐3d, Asylum Research) positioned above the microscope objective. Silicon tips with radii of about 7 nm  were used for probing topology and for applying a local force on the sample. The sample was excited by a CW diode laser (640 nm), resulting in 0.45 W cm−2 excitation power density at the sample plane after focusing the light by an oil immersion objective . The objective could be moved by a three‐axis piezoelectric translation stage. The sample holder was placed on top of a two‐axis piezoelectric translation stage belonging to the AFM. The sample holder and the AFM head were designed to create an almost closed volume around the sample. A small hole in the sample holder allowed to generate a small constant flow of argon gas to displace the ambient air. Light emitted by the sample was collected by the same objective and sent through a short‐pass filter to block the NIR laser light used in the AFM and a long‐pass filter to remove the excitation light. Then the emission was guided to a photon‐counting detector  and a spectrograph equipped with a CCD camera. Except the lasers and the spectrograph with the CCD, the whole setup was placed on a vibration isolation table and temperature stabilized to 28 °C by a closed isolation box. The relative humidity of the air inside the box was around 30%; see more detailed description of the setup elsewhere. It is noted that the AFM tip was probing/manipulating the top surface of the microcrystals, while the PL was excited and collected from the opposite side, through the glass cover slip on which the crystals were deposited : The tip was positioned above a desired location and a force–distance curve was measured. This curve : To scratch the sample, the AFM was used in the imaging‐contact mode, however only one line was scanned. The setpoint of the cantilever deflection (respectively the force) was chosen to be high enough, to achieve irreversible sample deformation. First the tip was brought into contact with the sample, then the preset force was built up and kept constant during the 1D scanning. Forces from 40 to 500 nN were applied.3Figure 3 microcrystal up to 100 nm thickness and about 1000 nm in diameter placed on a substrate and studied under an argon atmosphere. After acquiring these initial images, the crystal was scratched by the tip . After each vertical scratch, AFM images  and PL images  were recoded. The scratches are clearly visible from the AFM images. The first groove was so deep that the tip simply cut off a part of the crystal. The correlation between the AFM and PL images confirms that the same crystal was detected by both microscopes. Surprisingly, none of these drastic manipulations resulted in any PL intensity quenching of this crystal (PL images in (b) have the same intensity color code). An additional example is presented in Figure Panels a0 and b0 in Figure Considering that PL could potentially already recover during the delay between the mechanical action and the PL detection, we recorded PL transients simultaneously while scratching Figure 3. Befor Accordingly, the PL intensity distribution over the object may change over time. Another possibility is that some of these cut‐off nanocrystallites accidentally have a smaller number of deep defects than other nanocrystallites due to statistical fluctuations.We note that there is one location on the crystal shown in Figure 68 Acc these forces can be translated into pressures in the order of 0.1–3 GPa  than in an argon atmosphere (around 100 s), see Figure Because the recovery lasts from tens to hundreds of seconds, which is much longer than the characteristic time of PL fluctuations,70 we We also analyzed the initial response of PL to the force Figure . In 89% Figure We also found that PL recovery does not require light illumination and occurs also in the dark. t = 159 s) where after the initial strong quenching the PL recovered before the force was released. To observe this effect more often, we held the force for hundreds of seconds, which is much longer than in the experiments described above where the force was held for 10 s only. Figure t = 300 s it suddenly dropped again. The whole process looks as “attempts” of the crystal to recover its PL which, however, were only partially successful. Several more of such “attempts” can be seen in the curve until the pressure was finally released at t = 850 s allowing complete PL recovery. Cases of full PL recovery under pressure were also observed as illustrated in Figure It is interesting that even under constantly applied local force in some experiments PL recovery was observed. One example of this effect can be seen in Figure 44.13), which is often larger than the measured thickness of the studied crystals. The lateral dimension of the region where the PL was quenched was at least of the size of the PSF (400 nm in diameter) which again is much larger than the diameter of the tip/sample contact area  of the sample was affected. This fact alone can be explained by considering that 640 nm excitation light has a quite large penetration depth  under the force, and it takes even longer time for the PL to rise again (for the deformation to disappear) after the force is removed. The Voigt model of a viscoelastic solid allows to calculate the time evolution of strain ε under a time‐dependent stress σ (force)η and k are the viscosity and elasticity coefficients, respectively. In this model application of a constant force leads to an exponential increase of strain. When the force is removed, the strain decreases exponentially. Both processes are described by one characteristic time τ = η/k.If we do not consider PL blinking for a moment, the overall dependence of the PL on force looks like the dependence of strain (deformation) of a viscoelastic solid on an applied force. In a viscoelastic solid it takes time to build up strain under constant stress and it also takes time for the strain to disappear after the stress is removed. Literature data show that MHPs possess viscoelastic properties.73 Accε. This dependence PL(ε) must be the same when the crystal is under pressure and when the crystal relaxes after the force was removed, because it passes through the same range of ε: from zero to εmax during the PL decline and from εmax to zero during the PL recovery. Thus, by matching the PL decline and PL recovery trajectories in the coordinates of ε, we can find the characteristic time τ of the Voigt model. If the two trajectories match each other, it means that the theory can describe the experimental data. Indeed, the experimentally measured trajectories (PL decline and recovery) satisfy this condition quite well. By analyzing the shape of the obtained experimentally PL(ε) dependencies for different crystals, we found that it can be approximated by the following formula0 is the PL coming from the part of the crystal, which is not affected by the quenching; and kr and knr(ε) are effective radiative and nonradiative rates, respectively, in the part of the crystal affected by the force. β gives the strength of the force‐induced NR recombination in comparison with the radiative recombination. ε0 is the strain, the application of which increases NR recombination by e times, see the details in Note Figure β and ε0, however, vary from crystal to crystal much more broadly. This is not surprising considering the stochastic nature of the PL intensity of such small objects in general  model. When the PL goes up or down under constant light illumination, some parameters of the SRH+ model change during the macroscopic observation time t of the experiment.Next, let us discuss possible microscopic mechanisms behind the phenomenological dependence of the PL on strain [Equation ]. The PL+) model.60 Whet. The currently accepted picture of PL blinking in MHP microcrystals assumes that each crystal contains a small number of metastable NR centers possessing very large charge capturing and recombination cross sections  also indicates that some parameters of the SHR+ model (or any other recombination model) are stochastic and change abruptly during the macroscopic observation time   with rather low charge recombination cross section and very few supertraps in the active state (their number Ns < 10) with very high capturing and recombination cross sections. Ns is small and it fluctuates over time causing PL blinking. So, all parameters except Ns are continuously changing parameters, while Ns is a small integer number and thus changes only in relatively large steps .Without loss of generality, we can assume that there are two types of defects: common defects  states is random and rather rare, it does not need to happen exactly at the time when the force is applied. Let us consider a simple model for illustration  should be affected in the first place, because they possess active and inactive states to switch between, while it is more difficult to change nominally stable defects.3 is of the order of 1 s, which is far too short to account for 100 s recovery time often observed experimentally.After discussing several scenarios to interpret our observations, for the sake of completeness we finally want to exclude another seemingly obvious possibility. In principle, slow recovery after removal of force could be solely explained by the slowness of the supertrap switching. In this case, we would not need to involve strain as a slow‐changing parameter at all. We simply could assume that the equilibrium between the active and inactive states of the supertraps depends on force (stress) instead of strain. Contrary to strain, force can be applied and removed instantaneously. When the force is removed, the system becomes instantaneously nonequilibrated. To reach the equilibrium takes time, because the switching time from the active to inactive state is slow. However, such a scenario is unlikely, because as we discussed above, the maximum characteristic time of blinking in MAPbI4.43. We speculate that at the location where the force is applied, the material locally rebuilds in such a way that the region around the tip simply does not participate in electron‐hole dynamics any longer. For example, the crystal structure could change locally to a different phase with a higher bandgap compared to tetragonal MAPbI3 at room temperature. Indeed, it has been shown that under a relatively low pressure of 0.3 GPa there is a phase transition toward the higher bandgap orthorhombic phase. In this case the strain induced NR centers activated close to the tip may become isolated in this new high bandgap phase and their contribution to the NR processes in the whole crystal will decrease. Presumably, the charge carries will quickly escape this high bandgap region to the surrounding  where the bandgap is lower. The same mechanism has already been proposed to explain the highly inhomogeneous spatial distribution of PL intensity and PL enhancement in MAPbI3 microrods during the tetragonal–orthorhombic phase transition region at around 160 K without pressure. Note that the force of 40 nN applied in the experiments shown in Figure The discussion presented above cannot easily account for the recovery attempts and full recovery under stress (and strain) observed in a few cases Figures  and 8. Oic phase.41 In 4.5 Theoretically, averaging of all these responses over tens of thousands of objects and force application attempts  should lead to a response as one would measure in an ensemble. However, it is difficult to imagine an experiment which would directly give the ensemble‐averaged result of local force applications to small crystals. By studying small crystals individually, we deliberately avoid ensemble averaging to directly detect activation/deactivation of a single NR center. This gives us a much deeper insight on the processes and allows discussing mechanistic explanations of the otherwise ensemble‐averaged phenomena like PL intensity increase/decrease and self‐healing. So, we stress that the differences between the behaviors of different crystals do not contradict to the proposed explanation of the effect, on the contrary, they support it.Our experiments demonstrate that different microcrystals show very individual responses of their PL on the applied force Figures  –8. At a78 The4.63 depend on the surrounding atmosphere. The effect of a particular atmosphere can be either PL enhancement or PL decline depending on the stoichiometry of the sample. Different atmospheres also lead to very different PL blinking behaviors of MAPbI3 crystals. Accordingly, it is not surprising that we found statistically different PL recovery times of MAPbI3 crystals in air and in argon atmospheres. The role of oxygen and water in perovskite degradation and defect evolution has been discussed in numerous publications. Several plausible chemical reactions, involving the ions composing the perovskite and water and oxygen from the environment, have been proposed However, despite of these efforts it is still not possible to pinpoint with confidence the nonradiative recombination centers which are induced/inhibited by these reactions. Our experiments indicate that the presence of air accelerates the return of the system to the initial equilibrium, which might be related to an enhanced ion diffusion in the presence of oxygen and water (or H+) in the crystal. Note that since we observed PL recovery without light illumination, the diffusion of ions that leads to rebuilding of the crystal structure is not necessarily light driven.It is well documented that light‐induced transient effects in MAPbImosphere.79 The4.7 Numerous theoretical calculations suggest that iodide interstitials and atomic lead (Pb0) are deep defect states, which are expected to provide high charge trapping and recombination rates. In addition, defect complexes  whose association and dissociation could provide switching have been suggested. The simplest complex is a Frenkel defect pair—an iodide interstitial and an iodide vacancy. However, there is a problem in direct assigning the strong NR recombination centers to iodide interstitials or Frenkel pairs. Many XPS experiments have shown that in the few nm thick region near the surface of MAPbI3 the I/Pb ratio is around 3.6 instead of 3.0 expected from a perfect stoichiometry. This implies that thousands of iodide interstitials in the near‐surface region of a 100 nm × 100 nm × 100 nm crystal should be expected, while for PL blinking only a few metastable NR centers per crystal are needed. Based on this reasoning it can be concluded that the numerous iodide interstitials located close to the surface cannot be the quenchers we are looking for. There have been several distinct experiments suggesting that defect clustering is common in perovskites. Along these lines supertraps are not just single defects, but rather clusters thereof, which are responsible for NR recombination and material degradation. Defect clusters may have very different properties than the single defects they are composed of. Accordingly, it is not obvious that a cluster of deep defects promotes any NR recombination. At the same time, it is also not apparent that a cluster of benign defects (when isolated) stays benign. For example, a donor–acceptor pair  can be a strong nonradiative recombination center because it can efficiently capture both charge carriers at a very small spatial location. Discussing these various options, we have to admit that the chemical nature of the supertraps still remains an open question.Although there is compelling evidence supporting the presence of NR centers of different types with very different charge capturing and recombination cross sections, and their type and concentration depend on sample preparation, environment, light irradiation, and many other factors, it is not yet possible to pinpoint their exact chemical nature. Electrical experiments also give quite different picture of the defect types and concentrations in comparison with pure optical measurements.88 Num4.8 Although we cannot yet tell their chemical nature, we know with confidence that the supertraps are extremely efficient NR centers in comparison to any others. Indeed, for the PL intensity to drop by a factor of two by adding one supertrap, the induced NR rate should be at least equal to the total recombination rate . Considering this, we would like to explicitly formulate the following general question: Are there any other effective NR centers in MAPbI3 semiconductor except of the metastable supertraps?The phenomenological model of metastable supertraps in MHPs readily explains many transient effects of MHPs.35 Alt3 individual crystals and films and ii) PL quenching under strain likely occur due to stabilization of supertraps in their active state. These two observations strongly suggest that the metastable NR centers are indeed responsible for the majority of NR recombination in MAPbI3. This conclusion agrees well with the remarkable matching between the typical trap concentration obtained from PL studies of MAPbI3 thin films and the concentration of the metastable NR centers in blinking crystals prepared by the same deposition methods . Thus we can state that at the moment there are no experimental facts contradicting the hypothesis that a substantial if not the major part of strong NR recombination centers in MAPbI3 are metastable, while there are indications in favor of this hypothesis. Therefore, we finally reaching a match between the peculiar defect tolerance and self‐healing properties observed in bulk samples and devices and the fluctuation processes observed at the level of individual nano‐ and microcrystals. Remarkably, the self‐healing of the PL as well as its degradation and recovery can be explained by the evolution of supertraps and other metastable defects which switch from one state to the other in response to a change of the environmental conditions. Moreover, metastability of NR centers is a factor leading to apparent defect tolerance, which was not considered before. Indeed, despite of the existence of NR centers, their time‐averaged contribution to the overall NR recombination can be much less than one would expect form their concentration and trapping cross sections simply because the centers are active only a fraction of time due to their switching.We have the following crucial observations: i) PL blinking in MAPbI crystals26 and53 perovskite. Despite of the initial severe PL quenching triggered by the mechanical force applied by the AFM tip, complete self‐recovery of the initial PL properties of polycrystalline MAPbI3 microcrystals was always observed at a time scale of minutes. Indeed, while strain and crystal damage promote very efficient nonradiative charge recombination, this state of the material is not permanent. The semiconductor always returns to the initial balance between radiative and nonradiative charge recombination. The self‐healing process does not require light irradiation and depends on the surrounding atmosphere. The PL intensity of the studied crystals showed pronounced blinking. Upon application of the force, the PL intensity in >60% of cases dropped after some delay in just one or a few discrete abrupt steps in a similar manner as it fluctuates during PL blinking. These observations suggest that strain stabilizes the active (strongly quenching) state of the metastable NR recombination centers compared to the inactive state. Therefore, the whole PL quenching and recovery process is mostly driven by the dynamics of metastable NR charge recombination centers, the presence of which is corroborated by the PL blinking caused by them. The data suggest that it is highly likely that majority of efficient NR recombination centers in MAPbI3 semiconductor are metastable contributing to the defect tolerance property of the material. We propose a phenomenological model where the NR rate depends on strain induced by stress according to the Voigt model of viscoelasticity and found the characteristic time of strain relaxation in MAPbI3 to be on the order of 10–100 s. The ability of MAPbI3 to recover after mechanical damage is an extraordinary property for a crystalline semiconductor. It can be highly advantageous for future demanding applications of these materials.Correlative atomic force and confocal fluorescence microscopy allowed us for the first time to directly probe the influence of mechanical stress and local damage on charge recombination processes in MAPbIThe authors declare no conflict of interest.J.L. prepared the samples, participated in the experiments, did the initial data analysis, and took part in the coordination of data collection, and preparing of the first draft of the paper. M.G. carried out all experiments, collected all data, and participated in writing of the manuscript. IS designed the concept of the study and wrote most of the paper. P.F. developed the theory, modeled the experimental data, and wrote the theoretical part of the paper. T.B. participated in writing the manuscript and, together with IS, designed the experiments and coordinated the project. P.F. and I.S. with support of T.B. developed the physical interpretation of the experimental data.Supporting informationClick here for additional data file.


Objective: This pilot study explores a model for implementing communication routines including personal communication plans in long‐term residential care.Specific routines such as the development of personal communication plans can improve the interaction between people with communication disorders and healthcare staff. This multiple case study includes two residential care facilities that differ in size and the number of languages spoken. Intervention or main variables studied implementation strategies involved workshops, individual coaching and follow‐up visits. Main outcome measure implementation was assessed using goal attainment measurements, and the staff's views about facilitators and barriers to implementation were explored through structured interviews using the Theoretical Domains Framework.The overall implementation success rate for the facilities was moderate, and one of the facilities showed promising results related to personal communication plans. Both facilities experienced barriers to implementation, including management problems and a lack of reminders. However, the two facilities seem to have different motivations for change.Regardless of the features of the facility, successful implementation requires stable and committed leadership. Moreover, experiences with language diversity may motivate staff to implement communication routines.The content of the implementation model used  was coproduced by staff, managers and the researchers involved in this project. The staff and managers were responsible for the implementation of the new routines under the supervision of the researchers. Therefore, this pilot study explores a model for implementing communication routines, including personal communication plans for all residents, to facilitate PCC in two long‐term residential care facilities. This study has two aims: to explore the level of success in implementing personal communication plans as well as other routines supporting interaction and to present a preliminary exploration of facilitators and barriers to implementation.2Using an exploratory and multiple‐case design, this study examines two municipal long‐term residential care facilities for older people in the same district located in western Sweden. Before the present study, both facilities had taken part in a project to implement PCC that focused on incontinence. The participating staff in this project described difficulties providing PCC for residents with communication disorders, which led them to contact the authors of the present paper. That is, the intervention was initiated by the staff from the two participating facilities and the content of the intervention was planned and coproduced with the participants in this study.In Sweden, long‐term care is decentralized and highly subsidized as municipalities are responsible for institutional care such as residential care facilities, and approximately 95% of the cost is covered by county councils and municipalities as well as national taxes.2.1The first facility F1) has 20 one‐room apartments divided into three units. Two of the units offer dementia care and one offers care for those with physical disabilities. At F1, all available care staff working on the units (28 ENs) agreed to participate, and four of them became key ENs  has 43 one‐room apartments divided into three units: a dementia unit, a psychogeriatric unit and a unit for those with a physical disability. There were approximately 40 ENs working on the units. At F2, 28 of 40 ENs agreed to participate, and three became key ENs. At this facility, 25  provided background data and 27 ENs participated in the workshop. The ENs were 22–64 years old (medium: 47 years), had 3–41 years of work experience in healthcare (medium: 19 years) and had a variety of languages as their native/first language . Both authors are licenced SLPs and had previous experience working with individual staff communication training in residential care facilities. At the time of the study, the first author E. F. was a PhD student and C. S. was a researcher and E.F.'s main supervisor. During this meeting, the UMs and the SLPs discussed the time plan, and unit needs concerning communication including difficulties associated with speech‐language problems were discussed. Another important issue was making the management actively involved and to adapt the project to the needs of each unit. Between 6 and 12 weeks later, short information meetings (15–30 min) were held to outline the project and introduce the ENs. The UMs then checked the degree of interest among their respective staff.The first phase, which explored the 2.2.2During the second phase, the first author E. F. was present in the facilities for around 10 h per week for 2–3 weeks where they provided further information and recruited participants. During this phase, key ENs were recruited. The key ENs were responsible for the fulfilment of the unit's specific goals (see Phase 3) and served as a resource for their colleagues concerning communication matters in their units.2.2.3The third phase lasted 5 weeks and the first author E. F. was present in the facilities for approximately 15 h a week. This phase, which aimed to involve all available ENs, started with a meeting with the UM, 3–4 ENs and the authors E. F. and C. S. Preliminary goals for the whole unit were set based on the ENs' views on problems and resources. The main goal at both facilities was to draw up personal communication plans that complemented each resident's health plan. These plans were codeveloped by the ENs and residents , the following criteria were used: if the goal was not completed in any of the three units, the goal would be considered not attained; if the goal was completed in one or two units, it would be seen as partially attained and if the goal was completed in all three units, the goal would be considered attained. For the main goal of creating personal communication plans, a proportion of created plans related to the number of residents was calculated.To assess the level of success in implementing communication routines, a measure of 2.4To explore the facilitators and barriers to implementation, formalized interviews were conducted by the first author E. F. at follow‐up 4, a year after the workshops and goal setting. At F1, one EN  and the planner were interviewed. At F2, two key ENs (key EN1 and key EN3) were interviewed. The first author E. F. had previous experience in interviewing and had continuous contact with all the respondents during the implementation. All respondents were involved during the whole process of implementation (more or less) and agreed to an interview. The respondents have approached face‐to‐face and all accepted participation.An interview guide was constructed using the Theoretical Domains Framework (TDF).Because the interviews were guided by the TDF, a theory‐led thematic analysis was performed on the data.3Ethical approval for the study was obtained from the Regional Ethical Review Board of Västra Götaland in Sweden [reg no: 1016‐13]. Participants' anonymity was preserved, and they all gave their written informed consent. Participants were informed that their participation was voluntary and that they could withdraw their consent at any time. Extra care was taken in informing participating residents. They were initially approached about participating by one of the ENs working in the unit and were then asked again by the first author using picture support. The residents' significant others, family members or legal guardians were also informed about the study and gave written consent on behalf of the residents when required.44.1unit goal attainment showed that F1 had attained 40% of the main goal of creating personal communication plans for all residents at follow‐up 1, 75% at follow‐up 3 and 60% at follow‐up 4. Three of the other seven unit‐specific goals were partially attained and four were completely attained at follow‐up 4 , but 16% were attained at follow‐up 3 and 14% remained at follow‐up 4. Four of the seven unit‐specific goals were partially attained and three were completely attained at follow‐up 4  Management and key ENs; (3) Follow‐up and reminders and (4) Environmental resources. See summary in Figure The thematic analysis of interviews from F1 resulted in 118 items: 64 items coded as facilitators and 54 items as barriers. Analysis of interviews from F2 yielded 105 items: 75 items coded as facilitators and 30 items as barriers. All the facilitators and barriers are grouped into four subsections based on the content theme: (1) 4.2.1arranging activities according to language) was that residents did not always speak the same dialect or want to socialize. The personal communication plans  were described as a resource: ‘Communication plans, it's great, if it says in their files that you have a problem or what language or, it makes it easier (key EN1). Picture support materials  were described as particularly helpful and fun . Pictures were also perceived as sometimes helpful when dealing with people who had a different language background .The respondents saw the goals set as important but not demanding. However, not all staff were motivated. For example, one EN at F1 explained that not all staff had taken sufficient responsibility because some wanted to avoid additional tasks. At both facilities, staff perceiving interaction with residents as enjoyable and effective communication as crucial for accomplishing PCC were coded as facilitating. Respondents from F2 reported that it was a major problem when residents could not understand or make themselves understood due to communication disorders or language differences. It was also reported that communication problems could result in unnecessary medication administered by the staff to manage residents' anger and frustration. A barrier associated with goal 7  were not continuously active throughout the project. That is, most of the items relating to the management were coded as barriers.The planner at F1  talked about the importance of delegation and setting deadlines. The interviewed EN agreed: ‘It's really important that they also, you know, that they are involved throughout the process, you know, somehow they look and know which information we have received and what we know, they don't have the time, I understand of course, but it would surely be good’ . At F2, there were four UMs more or less involved throughout the project. The key ENs felt that the first two UMs, who initiated the project, saw it as important and assumed that it was because of these managers that the first goals were met. The key EN1 at F2 noted that the current UM's interest affects what is worked on and whether the staff continue to achieve the goals. In addition, it was also reported that two of the key ENs who were supposed to facilitate the change had begun working nights and the third had changed units.4.2.3Factors in the environment such as particular tools, staff availability and time were mentioned as both facilitating and hindering implementation. At F1, the fact that the goals were not financially costly was seen as facilitating. However, there were barriers. For example, the facility had been unable to purchase a table with wireless charging for tablets . A further problem was time. At both facilities, ENs reported that taking on extra work addressing goals would negatively affect colleagues. It was also noted that it was harder to meet the unit‐specific goals that required more planning and time. At F2, the opportunity to work in peace and quiet outside of the unit was cited as important for working on goals. The key EN3 explained that there were always interruptions in the unit that made it hard to focus on extra tasks.4.2.4Follow‐up visits were conducted by the first author on four occasions. These reminders of the goals were seen as facilitating. However, barriers included the lack of additional reminders and checks.At F1, although it was said that an outsider can ‘push to get things done’, no one on the units other than the first author followed up on goals . The planner explained that goals can be overlooked if one is not reminded, and the EN said there should have been more reminders about the goals at unit meetings. At F2, a few reminders other than the follow‐ups done by the first author were mentioned. For example, the second UM posted notes reminding staff to complete personal communication plans together with residents.5The two facilities in this study differed in the number of residents and staff and language diversity. The model explored here was moderately successful at both facilities implementing routines that facilitate PCC. By the final follow‐up, F1 had met four of eight and F2 had met three of eight unit‐specific goals. The main goal of implementing personal communication plans was quite successful at F1. At follow‐up 3, F1 had reached a 75% goal attainment rate (whereas F2 had only reached a 16% rate). Although this had decreased to 60% at F1 at the final follow‐up, this facility showed promising results in the context of implementation science.The two facilities showed both similarities and differences regarding the identification of facilitators and barriers to implementation. Both facilities had inconsistent management during the course of the project. Rokstad et al.A difference between the two facilities was found concerning the motivation for change. At F1, although the staff thought the subject was important, they expressed no urgency about making changesWe chose the two facilities for this study because they had expressed an interest in an intervention focused on communication during their participation in a previous project. The initiative to participate in the research came from the participating facilities, so the planning of the routines was mainly coproduced with the participants in the study. In an overview focused on the implementation of nursing interventions in dementia care, Karrer et al.The size of each facility may have also affected the participants' sense of community and responsibility during the project. F1 was approximately half the size and had half as many ENs employed as F2. This may have encouraged a greater sense of shared responsibility for the project and may explain why F1 managed their goal attainment more effectively. At F2, however, a higher percentage of the staff group participated in the workshops than at F1, and this may also have affected their sense of responsibility. Perhaps this, together with the strong desire for change, explains why, despite many barriers, F2 still managed to attain some of the goals.Another factor that was discussed by respondents as having an impact on implementation was the ability to actually take the time and focus on tasks connected to the facilitation of communication . In the context of residential care facilities, it has been seen that staff generally prioritize practical care tasks before aspects connected to person‐centredness .In implementation research, there is debate about whether a single or multiple implementation strategies are preferable.the particular process of implementation conducted.process evaluations.In relation to the broader field of implementation research, our study should be seen as one of the initial steps in a larger implementation effort as it contributes to knowledge of barriers and facilitators for implementation in the context of long‐term residential care. In a larger‐scale implementation effort, an explicit theory guiding implementation should be stated and a complete evaluation of 5.1Although neither of the facilities had managed to fully attain the goals set at follow‐up, F1 showed promising results regarding the main goal of developing personal communication plans. The success of the implementation was only monitored for 1 year and this was probably too short. Despite this limited timeframe, we could identify the rapid turnover of staff as a barrier to the development of new routines. Implementation strategies that focus on adaption to the unit and involve all staff may be facilitating but reminders are also needed. In line with previous research, our result implies that leadership and facilitation are crucial for successful implementation. Leadership on all levels  needs to be thoroughly planned and maintained consistently during the project. Also, the roles and responsibilities of each participant and priorities for direct care and tasks focused on communication need to be grounded at all levels in the facility. Another important lesson that can be drawn from our study is that ENs may find language diversity a more significant problem and is more motivating for finding communication solutions than the presence of acquired communication disorders. This result is important to keep in mind when introducing implementation efforts focused on communication in the context of residential care facilities in the future.Both authors Emma Forsgren and Charlotta Saldert have significantly contributed to the conceptualization and design of the study. The first author Emma Forsgren conducted the data collection and analysis. The second author Charlotta Saldert was involved as a discussion partner throughout the data collection and analysis and conducted interrater reliability assessments. The first author Emma Forsgren produced the first draft, and both authors Emma Forsgren and Charlotta Saldert contributed to the final version of the manuscript.The authors declare no conflict of interest.Supporting information.Click here for additional data file.


When CCT0 was less than 460 μm, the CRC slightly decreased as IOP increased. Meanwhile, the CRC increased as IOP increased if CCT0 was 570 μm. A constitutive mechanical model was proposed to describe the response of the cornea accompanied by the changes in IOP. In vivo measurements on human subjects under both noninvasive and invasive conditions revealed that the relation between the CRC on the IOP is much closer to those observed from FEP. Considering the observed structural deformation of human cornea, we found that FEP mimics the human eye more accurately than the CEP. In addition, the tonometry readings of IOP show that the values from the CEP were overestimated, while those from the FEP were not. For these reasons, we expect that the FEP could be suitable for the estimation of true IOP and allow performance testing of tonometers for medical checkups and other clinical uses.Comparative studies between artificial eyeball phantoms and in-vivo human subjects were carried out to better understanding the structural deformation of the cornea under varying intraocular pressure (IOP). The IOP-induced deformation and the tension of the cornea were measured by using an optical coherence tomography and noncontact tonometer readings, respectively. The dependence of the central cornea thickness (CCT) and corneal radius of curvature (CRC) on the IOP differed significantly between the full eyeball phantom (FEP) and cornea eyeball phantom (CEP) models. While the CCT changes were very similar between the two models, the relation between the CRC and the IOP was dependent on the type of eye phantom. For the CEP, the CRC drastically decreased as internal pressure increased. However, we found that the changes in the CRC of FEP was dependent on initial CCT under zero IOP (CCT The shapes of eye phantoms vary according to their purposes. Intraocular pressure (IOP), which is defined as the fluid pressure inside the eyeball and usually measured by tonometry, plays an important role in diagnosing glaucoma and in monitoring its progression and therapeutic response. Almost all tonometers estimate IOP by measuring the force required to deform the cornea. It is invaluable to use an eye phantom to mimic as accurately as possible the structural deformation and the tension of the cornea accompanying a change in IOP in order to ensure a reliable measurement.After the introduction of a phantom in the shape of a medication cup to evaluate the performance of artificial silicon vitreous implantsTo fulfill the requirements of the international standard for performance testing on a tonometer (ISO 8612), at least 120 human subjects should be tested with no more than 5% of the paired differences (± 5 mmHg) between the reference tonometer readings and the test tonometer readings. It is time-consuming and rather expensive to conduct large-scale population studies on human subjects to confirm that a tonometer meets this standard. To solve this issue, it is important to develop eye phantoms whose structural deformation and tension can be measured from the outside upon the application of IOP and whose characteristics mimic the human eye fairly well. Because most applanation tonometers measure IOP readings based on the force needed to flatten a predetermined area of the corneal surface, this force is a function of the stiffness and shape of the cornea. Thus, it is difficult to estimate the true IOP from tonometer readings without a detailed understanding of the contribution of IOP-induced deformation in addition to that of the corneal thickness. Most eye phantoms used for evaluating the performance of tonometers are fixed-cornea eye phantoms. This type of eye phantom mimics the deformation of the human eyeball only to a certain extent.11 on the biomechanical properties of eye tissues have shown that the tissues exhibit highly nonlinear stress–strain behavior as IOP increases. Using optical coherence elastography (OCE), Z. Han et al.9 reported an increase in the stiffness of enucleated porcine eyes after corneal collagen crosslinking treatment. J. J. Pitre et al.10 investigated the biomechanical properties of porcine corneas ex-vivo by using acoustic micro-tapping OCE and suggested that the biomechanical behavior of enucleated porcine corneas should be described with two different shear moduli. S. Park et al.11 investigated the relations between IOP and the biomechanical properties of the crystalline lens in enucleated bovine eyes by measuring the elastic waves propagating in the ocular tissues. A. Ramier et al.12 reported the shear modulus of 72 ± 14 kPa in human corneas in-vivo by using OCE.The deformation of the cornea due to IOP changes is expected to be governed by its biomechanical properties. Additionally, the biomechanical properties of ocular tissues including the cornea, sclera, ciliary body and lens are expected to affect tonometry readings. Many studies14. We also fabricated cornea eyeball phantom (CEP) and used them for comparative studies. We assessed the validity of these two types of eye phantoms for mimicking human subjects by measuring their structural deformation and noncontact tonometer (NCT) readings at varying IOPs. And then, we have carried out the comparative in-vivo measurements of corneal structural deformation of human subjects resulted from the IOP changes by both noninvasive and invasive method. In vivo measurements on human subjects clearly show that the dependence of the shape of the cornea on the IOP observed from human subjects is much closer to those observed from FEP.Corneal features account for more than 60% of human vision. However, there is no precedent works on the relation between IOP alterations and the shape of the cornea. When combined with the complex anatomical structure of the ocular tissues, the nonlinearity in the biomechanical properties makes it difficult to achieve a deeper understanding of the detailed relations between IOP and the deformation of the cornea. Here, we report a novel method to manufacture full eyeball phantom (FEP) made of the soft and flexible materials of polydimethylsiloxane (PDMS), which has been used for pharmaceutical and medical applications such as a glaucoma drainage implants and artificial skin0) of about 350 μm. For both eye phantoms, CCT decreased considerably with increasing IOP. The corneal radius of curvature (CRC) for the CEP decreased with increasing IOP, whereas an increase in the IOP of the FEP resulted in a less prominent decrease in the CRC. We took OCT images of the cornea with IOP changes at every 1 mmHg interval as the IOP increased from 0 to 45 mmHg, and we estimated both the CCT and the CRC . The overall changes in CRC for both model eyes as the IOP increased from 0 to 45 mmHg are shown in Table 0 values of 370 μm, 460 μm, and 570 μm are shown in Table 0. This may reflect the relative modulus changes accompanying the CCT0 changes. Thicker eye phantoms showed a higher NCT readings. Plots of the NCT readings versus IOP for FEPs with three different CCT0 values are shown in Fig. 0 increased, similar to what was observed in CEP. For all CCT0 values, the slope of the FEP plot was less steep than that of the CEP plot.Meanwhile, as shown in Fig. 0. All of the data were quite linear when the circumferential strain was small. From the circumferential stress– circumferential strain curves, the slopes for the CEP  strain accounts for the in-plane strain of the corneal surface of the phantom because the stress in the thin wall of the pressurized eyeball phantoms is one of the in- plane stresses. The circumferential stress and circumferential strain could be estimated from the data shown in Fig. pars plana vitrectomy is hardly affected by IOP change. It should be noted that the values of CRC and CCT shown in Fig. The deformation of human eyes induced by IOP changes was investigated by both non-invasive and invasive ways. Figure 7 developed a silicone eye phantom similar in shape to a contact lens, and used it to test a glaucoma diagnosis device. The Young’s modulus of the phantom cornea, a measure of its linear elasticity, was approximately 2.5 MPa, which differed from the physiological Young’s modulus of the cornea15. The CCT and CRC were approximately 210 µm and 8.2 mm, respectively, which were also inconsistent with those of real eyes. The CCT and the CRC of normal human corneas are in the range of 400∼600 μm18 and 7 ∼ 8 mm18, respectively. Hsu et al.8 developed an eye phantom for long-term IOP monitoring to test a lens-type sensor system. This eye phantom mimicked the pressure changes by using a micropump. Khan et al.19 developed an eye phantom with viscoelastic material for corneal elastography measurements. The CRC of this corneal phantom was 8.4 mm. Ko et al.20 developed a silicone eye phantom to characterize the corneal tangent modulus. The CCT and CRC of this eye phantom were 1100 µm and 8 mm, respectively. These phantoms all belong to the modular type. The cornea of these models is made of an elastic polymer to mimic the flexible tissues of a human cornea, while the other parts are fabricated from solid materials. The artificial cornea is usually fixed to rigid parts. These “fixed-cornea” eye phantoms have the advantage of being easy to fabricate and replace with materials of different structural and mechanical properties. However, there is no evidence that these CEPs can accurately mimic the structural deformation of the human eye. If the IOP increases or an external force is applied to the human eyeball, deformation occurs throughout the eyeball to maintain equilibrium. In contrast, in the case of a fixed-cornea eye phantom, any deformation occurs only in the cornea because the other parts of the eye phantom are rigid. For this reason, the deformation of a CEP in the presence of IOP changes and/or an external force would be quite different from that of a human eye. Furthermore, as the tension of the cornea is measured from the outside, the estimation of IOP could be affected.Deluthault et al.0. When CCT0 was less than 460 μm, the CRC decreased as IOP increased. However, when CCT0 was 570 μm, the CRC increased as IOP increased. When the IOP increases, deformation of the cornea should be mainly governed by its stiffness, which is determined by its material properties, structure, and boundary properties. At the boundary between the flexible and rigid parts of the CEP, the cornea extended significantly as the applied pressure increased under the constraint condition. This causes the axial length of the eye phantom to increase and there was an eventual decrease in the CRC accompanied by a decrease in CCT  can be expressed as follows22:Assuming that we set the region of interest near the corneal apex, the system can be considered to be part of a thin-walled spherical shell (see Supplementary Appendix). As the CCT is much lower than the CRC, the circumferential stress  and the shear modulus (G) is E = 2G(1 + ν). Therefore, the shear modulus can be estimated as approximately 93 kPa and 91 kPa for the CEP and the FEP, respectively. The values determined from our eye phantoms were close to the shear modulus of the human cornea, G = 72 ± 13.7 kPa23. These observations led us to propose that our eye phantoms could be utilized to investigate deformation of the eye caused by IOP changes or to measure the tension from outside the eyeball. Indeed, a recent study on the biomechanics of an in vivo human cornea showed that the corneal shear modulus was independent of both CCT and IOP12. This is consistent with the observations shown in Fig. c) – circumferential strain (εc) plot is independent of both CCT of eye phantom and IOP.Even if an information about the Poisson's ratio of the PDMS used in the construction of eye phantoms remains rather limited, the values might be close to the recently reported values 25, the observation from the current work is consistent with previous reports on the positive correlation between the tension measured from outside the eyeball and the CCT16. Meanwhile, the increment in the NCT readings due to the increase in IOP from 5 to 45 mmHg was approximately 1.5 times greater in the CEP than in the FEP ))9)) can 29. The Young’s modulus, representing the linear elasticity, was measured by a tensile method30. PDMS samples for tensile stress testing were prepared according to the ASTM D 412 standard. Dog-bone shaped samples with cross sections of 7 × 3 mm2 were used to measure the Young’s modulus of the PDMS samples. All the measurements were carried out within 3 days after the production of the phantoms.The eye phantoms used in this work were designed to have CCT values of 350 μm, 450 μm, and 550 μm, which are close to the average CCT of the human eyeball. After fabrication, we found that the CCT values with no applied force were 370 μm, 460 μm, and 570 μm. In addition, the CRC of the eye phantoms was designed to be 8.5 mm. The Young’s modulus of the PDMS phantom materials was adjusted to approximately 380 kPa by controlling the composition of the liquid PDMS mixture A syringe pump-based pressure control system  was used to control the internal pressure of the eye phantom. The CEP was connected to the pressure control system through a flexible tube , OCT images of the cornea were taken and used to determine both CRC and CCT.Volunteer patients seeking treatment at the Wonkwang University School of Medicine were recruited. This study followed a protocol approved by Institutional Review Board (IRB) and in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all subjects and/or their laga guardians, The age of the subjects ranged from 53 to 79 years. For in vivo studies on human subjects, we performed both noninvasive and invasive ways. Glaucoma is characterized by high IOP and should be decreased to normal with medication of topical and/or systematic drug prescription without any invasive maneuver to the eye. Individuals with an IOP beyond 60 mmHg before medicinal treatment were excluded from the study due to corneal edema and haziness. CRC as well as IOP of three patients with secondary glaucoma and two patients with primary open angle glaucoma were investigated before and after medication by using a refractive power/corneal analyzer  and a pneumatic tonometer , respectively. CRC and IOP were measured at least 4 h after drug treatment. Invasive studies on the human subject was carried out during Supplementary Information.


In the mathematical description of dynamic atomic force microscopy (AFM), the relation between the tip–surface normal interaction force, the measurement observables, and the probe excitation parameters is defined by an average of the normal force along the sampling path over the oscillation cycle. Usually, it is tacitly assumed that tip oscillation and force data recording follows the same path perpendicular to the surface. Experimentally, however, the sampling path representing the tip oscillating trajectory is often inclined with respect to the surface normal and the data recording path. Here, we extend the mathematical description of dynamic AFM to include the case of an inclined sampling path. We find that the inclination of the tip movement can have critical consequences for data interpretation, especially for measurements on nanostructured surfaces exhibiting significant lateral force components. Inclination effects are illustrated by simulation results that resemble the representative experimental conditions of measuring a heterogeneous atomic surface. We propose to measure the AFM observables along a path parallel to the oscillation direction in order to reliably recover the force along this direction. This theory specifically predicts the distant-dependent frequency shift of a tip moved perpendicular to a surface for a given force curve. Inversion formulae are available that allow for the extraction of the interaction force from measured frequency-shift data . The tip trajectories during single oscillation cycles at one fixed  are indicated for each case by dashed lines in To illustrate the effects resulting from an inclined tip oscillation, four cases are discussed. Common to all cases is that the data recording path, described by the oscillation centre positions  along the tip path is a scalar quantity and shown for α = 45° in  . However, similar effects can be present when using parameters for other sensors as well. Frequency shift Δf data are calculated with the piezo axis located at xts = yts = 0 and moving the tip along zp for data recording, while data are plotted as a function of The force gradient  = . When positioning the tip along the -axis for data acquisition, this case allows for a reliable determination of the interaction force  by applying known inversion strategies  with Δx = −Asinα and Δz = A(1 − cosα) from  The resulting Δf(3) data included as a dashed red curve in Next, the tip inclination is set to α = 12.5° within the f curves in the regime  ≫ 1 nm.When further increasing the inclination angle α as in case (4), the deviation becomes larger as presented by the violet dotted curve in  and  violates a fundamental assumption of the commonly used inversion algorithms [f data recorded along  As is apparent, the force curve does not match the model reference curve,  included as the solid black line. In contrast, the force curve recovered for the vertical oscillation and vertical data recording  matches the reference curve.The difference in the orientation of gorithms –5: The t describing the tip oscillation. This modification leads to an overlap of the tip sampling path segments for nearby positions along the data recording path. Therefore, the deconvolution using the known algorithms can be performed in the usual manner. Naturally, the result will not represent the perpendicular force  but rather describes the force component  along the w-axis, parameterised by the scalar variable  For a conservative force field, the vertical interaction force could in principle be calculated from this result. Additionally, if the full force field is of interest, this can be extracted by systematic measurements of many Δf curves using the appropriate experimental procedures [As a solution to this issue, we propose to orient the recording path for acquiring the AFM observables and parameters parallel to the tip sampling path ocedures .w-axis is different from the vertical interaction force along Simulation results for moving the tip along the inclined path during data acquisition and extracting the force along this path are presented in Several conclusions can be drawn from extending the mathematical description of dynamic force microscopy by arbitrary tip sampling and data recording paths. For a typical inclination of α = 12.5°, the minimum force was calculated to differ by more than 5% when compared to a result not taking the inclination into account. The magnitude of this difference depends on the model parameter choice and geometry: The difference can be amplified or reduced depending on the oscillation amplitude, on the interaction potential strength and decay, as well as on the atomic geometry. For example, edges of finite atomic slabs or larger atomic clusters generate significant effects. In practice, a model calculation is required to determine the uncertainty in the measured force due to the inclined tip oscillation.w, is aligned parallel to the tip sampling path, here described as the vector  The resulting measured force represents the component  of the tip–sample force along this direction. Despite the formal and quantitative difference from the commonly considered vertical component  the component along w delivers identical physical insights into the tip–sample interaction.Precise forces are measured if the data recording path, here introduced as the axis  defined byThe first AFM equation follows from evaluating the Fourier coefficient The tip–sample force can furthermore be written as a sum of an even and an odd force evaluates to zero. We compare this equation by introducing the equation of motion ( and using the fact that the time average is a linear functionalBy definition of an odd force, the time average f motion  for  and and qs = ⟨q⟩t. The first AFM equation directly follows asWith the harmonic approximation  it can d is defined asThe Fourier coefficient Within the harmonic approximation , this te be expressed by even and odd forcesand  evaluates to zero. Using the equation of motion (whereby the average f motion , the FouIn full analogy to , this eq are used.whereby the identities  is defined asThe Fourier coefficient which can be written asby using the harmonic approximation,  evaluates to zero. Using the equation of motion, whereby  this term evaluates toWith the identities


When making a goal-directed movement towards a target, our hand follows abrupt background motion. This response resembles that of a shift in the target’s position. Does background motion simply change the position towards which the movement is guided? If so, the response to background motion should resemble the response to a target displacement. To find out whether this is the case, we ran two exploratory studies where we asked participants to hit a moving target at a specified moment. At various times during the hand’s movement, the background could move briefly at one of several speeds, and for various durations. The response to abrupt background motion was larger when the background moved later in the movement and when the background moved faster, in line with known responses to target displacements. The response to a second epoch of background motion was smaller than it would have been if there had been no first epoch, in contrast to responses to multiple target displacements. If the background was already moving before the target appeared, the hand even moved in the opposite direction. Thus, the response to background motion and that to a target displacement are clearly not identical, but they do share several features. There is abundant evidence that people use many aspects of visual information to guide their goal-directed movements. This is often studied by changing visual information when the movement has already started. This method has be used to show that people respond quickly to changes in several attributes of a target including its position  volunteered to take part in Experiment 1 and 12 different participants  took part in Experiment 2 in return for course credit. The study was part of a research programme that has been approved by the local Ethics Committee in accordance with the Declaration of Helsinki. All participants gave written informed consent and were debriefed at the end of the experiment.The experiment was conducted in a normally illuminated room. The stimuli were back-projected at 120 Hz with a resolution of 800 × 600 pixels onto a 1.25 × 1.00-m acrylic rear-projection screen  tilted backward by 30 degrees. Participants performed the task using their dominant index finger while standing in front of the screen  with the stimulus presentation, the camera also recorded the position of a second marker attached to the side of the screen. This static marker stopped emitting infrared light when a light sensor at the top left corner of the screen detected light. On each trial, we presented a flash at this position when the target was presented, when the background motion started and ended, and when the screen was hit. The briefly missing marker enabled us to synchronize the movement recording with the stimulus presentation, so we could determine the onset of perturbations and performance (e.g. whether the target was hit) at 2 ms resolution.The starting screen consisted of a green starting point (2 cm diameter) presented 20 cm below the screen centre, a red horizontal bar (115 cm × 2 cm) 10 cm above the screen centre and 250 black dots (1.4 cm diameter) randomly positioned across the grey background. To start a trial, participants placed the index finger of their dominant hand on the starting point, so they could rest whenever they wanted to by not placing their finger at the starting point. After between 500 and 700 ms, the starting point disappeared and a blue horizontal target bar (115 cm × 2 cm) appeared 30 cm above the screen centre. It immediately started moving downward at 30 cm/s. If participants lifted their finger from the starting point before the blue target appeared, the target bar did not appear and they had to place their finger back at the starting point. Participants were instructed to hit the blue moving target bar when that bar was aligned with the red static bar by lifting their finger off the screen and then tapping the screen at the correct time and location. The two bars were perfectly aligned 667 ms after the blue bar appeared. This allowed sufficient time for us to present (and manipulate) the background motion and still capture the response of the hand before the interception took place. The red bar was always at the same place and both bars covered the full width of the screen such that the emphasis was on hitting the screen at the right vertical position and time.2 in the direction away from the screen. We interpolated the position of the target between image presentations. We considered the target to have been hit successfully if the calibrated marker position was within both the target and the static red bar at the moment of the tap. If participants successfully hit the target, the target remained at the position at which it was hit for 500 ms and a tone indicated that the hit was successful. If participants hit the target, but above or below the red static bar, the target stopped but there was no tone. If participants hit above or below the target, the target was deflected away from the finger at 100 cm/s , also remaining visible for 500 ms unless it left the screen before that. This feedback allowed the participants to keep their movements calibrated both spatially  were excluded from subsequent analysis. All other trials were included, irrespective of performance . We converted the measured lateral positions of the finger into (signed) lateral velocities by direct differentiation. This was done for every 2 ms interval. For each participant, we then took the median lateral velocity of the finger for every moment separately for trials in which the background moved leftward and those where it moved rightward. We subsequently determined the (signed) endpoint effect (mean and standard error across participants) depends on the amount of background motion, we plot the endpoint effect as a function of the difference between the overall displacement of the background for leftward and rightward motion for each condition . To explore how this endpoint effect depends on the time with no motion at the end of the movement, we also plot the endpoint effect as a function of the time from the offset of (the last episode of) background motion until the time of a perfect hit (667 ms after target appearance).To get a qualitative impression of the vigour of the response, we analyse the time-course of the responses to background motion (mean and standard error across participants). To quantify the overall influence of the perturbation, we subtracted the median movement endpoint for leftward background motion trials from that on rightward background motion trials to obtain the difference in movement endpoint for each participant in each condition. To explore how this To investigate whether the response to background motion is time-dependent, we manipulated the timing of the onset of the background motion. To investigate whether the response is proportional to the displacement of the background, we manipulated the speed and duration of the background motion. By comparing conditions with different numbers of epochs of motion, we assessed whether the response to background motion depends on preceding epochs of background motion. This resulted in twelve experimental conditions Fig. . For eacIn the Opposite Directions condition, the background moved sequentially in opposite directions on any given trial  276 ± 29 ms after the target appeared . They hit the screen 666 ± 12 ms after the target appeared, so on average they hit the moving target when it was aligned with the static bar, but there were some individual biases. They hit both bars (successful hits) on 71 ± 10% of the 720 trials. Figure The magnitude of the response is larger when the perturbation occurs later in the movement, showing that the response is time-dependent Fig. A. It is A possible reason for the response to a second motion onset being smaller than that to a first  with responses to continuous background motion starting at the same moment  For each of the six conditions, there was leftward background motion on 30 trials and rightward background motion on 30 trials. This totalled 360 trials with all conditions randomly interleaved. There was a single session that was completed in a single visit to the lab and took approximately 30 min.In all conditions the background moved at the same speed as in most conditions of experiment 1: 100 cm/s. In the continuous conditions, after the background dots first started moving laterally they continued to do so until the end of the trial. In the abrupt conditions, the background dots moved for a single epoch of 100 ms.Participants left the starting point (moved 1 cm in the direction of the target) 289 ± 46 ms after the target appeared . They hit the screen 670 ± 9 ms after the target appeared, so on average they hit the moving target when it was aligned with the static bar. They hit both bars (successful hits) on 62 ± 9% of the 360 trials. Figure We confirmed that the response is negative if background motion is present before the target appears and positive if the background motion starts at the time of the target appearance or later Fig. A. ExtendTo examine how the response might correspond with a (possibly temporary) shift in the planned endpoint of one’s action, we determined the effect of background motion on the movement endpoints. Specifically, we examined how the endpoint effect depended on the total displacement of the background and on the time from background motion offset until interception. The endpoint effect increases with the total background displacement up to a displacement of about 60 cm; larger displacements have no additional effect Fig. A. The enIn this paper we investigated the extent to which the response to background motion resembles the response to target displacements. Since both responses could be interpreted as the consequence of guiding the hand to an updated planned endpoint, we expected them to be modulated by similar factors. Motion that occurred later in the movement resulted in a larger response of the hand, showing that the response to background motion is time-dependent, in line with the response to target perturbations  but also re-evaluate where one can best hit the target . In line with the response to target displacements, the response to background motion is time dependent: the response is larger when the background motion occurs later in the movement. There is also some evidence that the response to background motion is proportional to the speed and size of the background displacement. However, the response to multiple epochs of background motion is not independent and the sign of the response is determined by the timing of the onset of background motion. Although the response to background motion and target displacements are not identical, they do share several features. Thus, we propose that the onset of background motion temporarily shifts the position towards which movements are guided, but that this position gradually shifts back if the background stops moving.


In mining safety and other fields, similar material simulation is the main research method to study the movement and deformation of rock formation and ground surface. However, the inaccurate subsidence laws could be obtained because the strength of the composition materials like gypsum and lime is easily affected by moisture. Therefore, it is crucial to monitor the moisture content when carrying simulation experiments. This paper discussed the feasibility of indirectly measuring the moisture content of similar material models using the three-dimensional (3D) laser scanning reflection intensity through three experiments on similar material specimens. The results showed that the laser reflection intensity was sensitive to the moisture content, incidence angle, and distance with three different relationships and the influence of the two factors could be weakened through the established correction models. However, it was recommended restricting the incidence angle to less than 20° and setting the distance from 4 to 10 m to reduce the complexity of correction. The accuracy of this method reached 1.1% under the monitoring condition of 4 m and the normal incidence, which could meet the requirements for monitoring the moisture content of similar material models. The research results of the paper provide a new method to monitor the moisture content in similar material models. Therefore, the subsidence induced by mining and its laws should be predicted accurately and studied carefully for alleviating environmental and geological problems. Generally, physical simulation and numerical simulation are the main research methods in the fields of rock formation movement and surface subsidence. And physical simulation has been widely used in this area based on its direct-viewing observation of the internal movement and deformation of rock mass in various continuous and discontinuous simulations3. The method of similar material simulation, a common physical simulation method, generally uses sand, gypsum, lime, and some other materials to construct models4. During the excavation of a model, the movement and deformation in the rock formation and the ground surface of the model are monitored. Based on the established similarity theory between the model and the prototype, the movement and deformation of the prototype could be estimated from the monitoring results. This simulation research method has been applied in many fields such as coal filling mining, overburden failure evaluation, stope pressure, stability of goaf, etc.5. However, it should be pointed out that gypsum and lime, which are usually used as the cement of models, are air-hardening materials whose strength is influenced by the moisture content in the air. Hence, it is inevitable that the strength of the model composed of gypsum, lime, and sand might change due to the variation of moisture content7. Under natural conditions, the water in the model would gradually evaporate, which could make the strength gradually increase and even largely deviate from the designed strength. At this time, the correlation between the model and the prototype does not accord with the established similarity theory, which would lead to the wrong results if the unsuitable model is used to carry out the simulation study of rock formation.Underground coal mining could lead to the movement and destruction of overlying rocks, resulting in a large area of surface subsidence and deformation, which would bring a series of environmental and geological issues8 suggested that the strength of a mixture of sand, lime, and gypsum was directly related to its moisture content. When the moisture content was controlled within a certain range, the strength of the mixture was stable. Therefore, it is necessary to control the moisture content when conducting the model experiments. On the one hand, the moisture content should be confined within the appropriate range; on the other hand, an advanced warning is required to let experimenters know that the strength of the model has deviated from that of the originally designed model when the moisture content of the model exceeds the range.Data from the study9, neutron method10, time-domain reflectometry (TDR) method13, frequency-domain reflectometry (FDR) method15, distributed optical fiber sensing technology method17, etc.; the non-contact measurement methods mainly include near-infrared method18 and microwave measurement method19, and others. However, the contact measurement mostly belongs to the point measurement with a small measurement range and could cause certain damage to models, while the non-contact measurement has significant advantages on measuring the entire models with little disturbance to the models themselves.Methods for monitoring the moisture content of mixtures that consist of sand, gypsum, and lime can be generally divided into contact measurement methods and non-contact measurement methods. The contact measurement methods mainly include drying method22. In addition, Junttila et al.23 and Zhu et al.24 have retrieved the moisture content of plants utilizing the laser reflection intensity by the fitting model created by the laser reflection intensity and the moisture content. However, it is still necessary to correct the laser reflection intensity value to weaken the effects of incidence angle and distance before retrieving23. Although the accuracy of the intensity value is related to many factors such as material composition, color, surface texture and roughness, incidence angle, distance28, and some others, the incidence angle and distance are the main influencing factors as far as a specific reflective medium is concerned29.The three-dimensional (3D) laser scanning method, a non-contact measurement method using near-infrared light, has significant advantages in monitoring the moisture content of a model. For example, a 3D laser scanner can simultaneously measure the displacement field of the model after mining and the moisture content of the model. The basic principle of the method to measure the moisture content is to use the physical mechanism that the laser reflection intensity is significantly lower than the laser emitted intensity since the laser energy is absorbed by the moisture in the model. Specifically, the material with higher moisture content has a much stronger absorption of the laser energy, which could cause the lower reflection intensity of the laser and vice versa. The method of monitoring the moisture content using a 3D laser scanner is currently used in monitoring the moisture content of ancient buildings, vegetation, and energy source30 and (4) whether the accuracy of the method could meet the monitoring requirements on the moisture content of similar material models.Therefore, there are still many uncertainties about applying this method to the moisture content monitoring of similar material models, which include: (1) whether there exists a significant correlation between the laser reflection intensity and the moisture content of a similar material model; (2) whether incidence angles and distances have disturbance to the sensitivity of the laser reflection intensity to the moisture content; (3) whether the laser reflection intensity can be corrected to the same standard for comparison because the incidence angle and distance of the laser beam corresponding to each scan point are different in actually periodic observationTo ascertain the above problems, the similar material specimens are investigated through three experiments in this paper to (1) explore the relationship between the laser intensity and the moisture content for determining whether the laser intensity is sensitive to the moisture content change; (2) study the influence of incidence angle and distance on the laser intensity to find the correction method and give some suggestions about the suitable monitoring position when using 3D laser scanning and (3) discuss the accuracy of this method. Based on the results, we discuss the feasibility of using a 3D laser scanner to monitor the moisture content of similar material models.31. A total of 10 specimens with a side length of 12 cm and a thickness of 3 cm were made according to the ratio. Some specimens were shown in Fig. 6. The REIGL VZ1000 3D laser scanner was used to monitor the moisture content in these experiments.Gypsum and calcium carbonate were selected as cement and sand was used as aggregate for making the specimens. The proportion of materials  evaluate the sensitivity from the relationships between the laser reflection intensity and the moisture content of the specimens; (2) explore the composite correlation of the laser reflection intensity and two factors and how to correct it and (3) study the accuracy of this method by comparing the retrieved moisture content with the results measured by the drying method6, while other three specimens were scanned at normal incidence with a measurement interval of 48 h at 4, 6, 8, and 10 m, respectively.To begin this process, a specimen was scanned at 4 m and the normal incidence with a measurement interval of 24 h and subsequently scanned at incidence angles from 20° to 80° in steps of 20° with an interval of 48 hEvery specimen was immediately weighed and correspondingly recorded after each scanning. After the whole scanning, all specimens were dried and their moisture contents during each scan were calculated by the drying method.The original laser reflection intensity of the obtained point cloud belonging to the area of similar material specimens was extracted and output by using the supporting Riscan software.30. To simplify the calculation, the obtained original laser reflection intensity was normalized to between 0 and 1 according tox is the original laser reflection intensity output by Riscan software and y is the normalized laser reflection intensity.The original laser reflection intensity is the ratio, which is mostly below zero, of the echo amplitude of the scanned target to that of the white plane Lambertian at the same distance and the normal incidence angle under the extended target conditionsAfter the conversion, the average normalized intensity was regarded as the laser reflection intensity of each scanning and the fitting model between the laser reflection intensity and the moisture content of the specimens was built and analyzed.The second experiment mainly studied the laws of laser reflection intensity responding to the incidence angle and distance change of the specimens at two moisture contents which were calculated as the process in the first experiment. For an obvious comparison, the two moisture contents were less than 2% and higher than 4% respectively. The specimens were placed at measuring distances of 2 m, 4 m, 6 m, 8 m, and 10 m, respectively. At each distance, they were rotated in steps of 10° according to the paper  is the established correction function, C is the correction coefficient obtained from f.Then, based on the selected normalization standard, the correction models were also established to correct the laser intensity dataTo study the accuracy of the method, the moisture contents obtained through laser scanning were compared with the actual moisture contents of each specimen. The incidence angle and distance were set at 0° and 4 m. After each scan, the specimen was also weighed and the subsequent process was the same as that in the first experiment.The ambient temperature and humidity of the three experiments were the same, while the scanning method see Fig.  was diffAccording to the fitting model built in the first experiment, the moisture contents of the specimen were retrieved from its laser reflection intensity and compared with its actual moisture contents calculated by the drying method. The difference of the data obtained through two different measurement methods was used to calculate the RMSE based on Bessel’s formula and the RMSE was utilized to describe and evaluate the accuracy of the 3D laser scanning method under the monitoring condition of 4 m and the normal incidence.The correlation between the laser reflection intensity and moisture content was studied based on the specimen monitored at 4 m with the normal incidence angle using the 3D laser scanner. In Fig. The derivative relationship showed this difference more clearly. From the chart, it could be seen that the absolute intensity change rate was from 0.02 to around 0.04 when the moisture content was less than 4%, while it dropped from 0.02 to 0.01 when the moisture content exceeded 4%. The results, as shown in the derivative fitting model, also indicated that the absolute value of the intensity change rate increased nonlinearly with the moisture content decreasing and still existed even the moisture content has been to 10%.The results of the correlational analysis among the intensity and moisture contents, including 0.55%, 1.43%, and 6.35%, were shown in Fig. Figure Figure The above could be seen more intuitively from the first line chart. From this chart, the change in laser reflection intensity between 2 and 4 m was greater than that from 4 to 10 m, showing a significant characteristic of a piecewise function. In addition, with the moisture content falling, the distance had a significantly stronger effect on the intensity of the same incidence angle.The last illustration in Fig. The above data obtained under the two moisture contents were corrected to different standards, including 4 m, 6 m, and 8 m under the normal angle, through the established correction models. The parameters of the correction formulae with different normalization standards were shown in Table Figures Taking the standard intensity values as the true values, the root-mean-square errors (RMSEs) of the corrected laser reflection intensity were shown in Table It could be seen from the data in Table To evaluate the performance of using 3D laser scanning to monitor similar material specimens, we analyzed the feasibility of the monitoring method based on three experiments from the three aspects of sensitivity, influencing factors, and accuracy, respectively.24, indicating that the laser intensity is sensitive to the change of moisture content during the monitoring process. Therefore, for some similar material models designed under about 10% moisture content35, 3D laser monitoring could maintain sensitivity during the process of moisture content′s gradual loss.In the changing process of the specimen from the highest moisture content to the lowest moisture content, the laser intensity increased exponentially in Fig. 36. Therefore, in the optimum observation interval, this high sensitivity is relatively beneficial for monitoring the moisture content change. Moreover, this sensitivity would not be significantly affected by the incidence angle and distance, as proved by the fact that the similar relationships between the moisture content and the laser intensity at different positions (see Fig. In addition, the relationship between the laser intensity and the moisture content demonstrated that when the moisture content was less than 4%, the laser intensity had a significantly greater response to the moisture content in Fig. see Fig. .From the above, for most of the similar material models, the change of moisture content could be detected using 3D laser scanning.24. Correspondingly, the relationships among laser reflection intensity, incidence angle, and distance would be diverse under different moisture contents (see Fig. The laser reflection intensity at the same angle and distance of 0.55% moisture content was higher than the intensity of 6.35% moisture content in Fig. 30. However, there existed an obvious feature of the relationships between the intensity and distance, a large attenuation at 4 m in the two surface diagrams of Fig. 29, while the small fluctuations at 6 m might be due to the errors. And the close-range effect turned to be greater as the moisture content dropped (see Fig. 24 reported that the laser intensity of the material with higher reflectivity had a greater attenuation as the incidence angle increased comparing with the material with lower reflectivity. Similarly, we also found that the effect of incidence angle and distance on the laser intensity increased as the moisture content decreased (see Fig. The relationships of the two influencing factors and the laser reflection intensity under the two moisture contents in Fig. see Fig. . Zhu et see Fig. .30. It would be more complicated for the correction to the intensity of the point clouds in different positions of similar material models with different moisture contents, which can also be inferred from the calibration process. Although the corrected intensity value is closer to the standard value, the workload of correcting is too complex after each real-time monitoring.Therefore, the influence of the incidence angle and distance would be diverse due to the different moisture contents, which could lead to the different composite relationships among the incidence angle, distance, and intensity under different moisture contents, and then the laser intensity correction models established from the composite relationships are also different (see Table For reducing the complexity of correcting, we recommend that the incidence angle should be within 20˚ and the distance should be controlled from 4 to 10 m when using a scanner to monitor similar material models. This is because Fig. 34. When the model’s moisture content was lower than 2% or higher than 4%, the difference between the retrieved moisture content and the actual moisture content would be larger (see Table The accuracy of the method was just 1.1% under the monitoring condition of 4 m and the normal incidence. The optimum interval to conduct the simulation experiments was the moisture content of about 2–4%34, the strength of the model could be clarified at any time to determine whether it meets the similarity theory and is suitable to carry out the simulation experiments.Therefore, the moisture content of the similar material models within about 10% moisture could be determined by the established fitting model between it and intensity under the premise that the incidence angle and distance are within the suggested range. Specifically, it is first necessary to limit the relative position of the 3D laser scanner and the similar material model in the practice. For example, the scanner could be placed in the middle and at a distance of 4 m from the model and the height of the scanning center should be the same as the model center. Then the overall point cloud data of the similar material model could be retrieved to obtain the overall moisture content of the model based on the established relationship between the moisture content and the laser intensity at 4 m and the normal incidence angle. And then based on the relationship between the strength and the moisture content of the modelThough the composite relationships among the reflection intensity and incidence angle and distance of different moisture contents are different, the reflection intensity all decreases nonlinearly with the incidence angle increasing and has obvious piecewise characteristics from 2 to 10 m.For different moisture contents and naturalization standards, different correction models need to be established to weaken the influence of incidence angle and distance. It is recommended that the incidence angle should be within 20° and the distance should be controlled in the range of 4–10 m to reduce the complexity of correction during actually monitoring.The laser reflection intensity gradually increases exponentially with the decrease of moisture content. The laser intensity is sensitive to the moisture content in the process of its evaporation and could even be more sensitive in the optimal monitoring interval for the similar material models of about 10% moisture content, which is hardly affected by the incidence angle and distance. The accuracy of 3D laser scanning is 1.1% under the monitoring condition of 4 m and the normal incidence, which could satisfy the monitoring requirement of the moisture content.In this paper, 3D laser scanning technology is used as a general data acquisition method to monitor the moisture content of similar material models. We prove the feasibility of this method from three aspects by the experiments of similar material specimens. We have discussed the sensitivity and relationships among the laser reflection intensity, moisture content, incidence angle, and distance. Then, the accuracy of the method has been also calculated. Through a series of experiments, we find that.To our knowledge, the above provides new ideas for the laser scanning technology to monitor the moisture content, our findings could be considered to provide a new way to monitor the moisture content of similar material models.Supplementary Tables.