Graphene is a highly versatile two-dimensional material platform that offers exceptional optical and electrical properties. Of these, its dynamic conductivity and low effective carrier mass are of particular interest for optoelectronic applications as they underpin the material’s broadband nonlinear optical absorption and ultra-fast carrier mobility, respectively. In this paper, we utilize these phenomena to demonstrate a high-speed, in-fibre optical modulator developed on a side-polished optical fibre platform. An especially low insertion loss (<1 dB) was achieved by polishing the fibre to a near atomically smooth surface (<1 nm RMS), which minimized scattering and ensured excellent contact between the graphene film and the fibre. In order to enhance the light-matter interaction, the graphene film is coated with a high index polyvinyl butyral layer, which has the added advantage of acting as a barrier to the surrounding environment. Using this innovative approach, we have fabricated a robust and stable all-fibre device with an extinction ratio as high as 9 dB and operation bandwidth of 0.5 THz. These results represent a key step towards the integration of low-dimensional materials within standard telecoms networks. Graphene is the most prominent of an emerging catalogue of two-dimensional materials that are currently spear-heading intense research across the optoelectronics community23710An alternative approach that offers a straightforward route to ultra-fast modulation is to exploit the strong saturation of graphene’s absorption due to Pauli blocking, whereby the generated carriers fill up the valence bands preventing any further transitions. By employing a pump-probe scheme, all-optical modulation has recently been demonstrated in a graphene-coated microfibre device with an operation speed approaching 200 GHz1013In this paper, we present a robust, all-optical modulator with a large 9 dB extinction ratio and an operation bandwidth of 0.5 THz. The device is built into a side-polished window of a standard optical fibre and is thus immediately compatible with existing fibre networks. By retaining a small cladding buffer between the core and the polished window, the insertion loss of the device is less than 1 dB, which represents a record low value for this type of device1516−1 full width half maximum (FWHM) of the 2D peakSchematic representations of our graphene-coated modulator are illustrated in To illustrate the principle of the enhanced light-matter interaction, the longitudinal cross-section of the device is shown in We start our investigations of the transmission properties of the graphene-PVB device by comparing the losses of the TM and TE modes using a polarized continuous wave (CW) laser at 1550 nm. The input power was set to 0 dBm and the polarization was tuned between the modes using a half wave plate. When coupling into the TE mode of the device, the reduction in output power was <1 dB, which is commensurate with insertion losses of commercially available fibre devices. The experiment was repeated again for the TM mode and the power was at a minimum of −31 dBm, as expected for our CVD-produced graphene film. This large, 29 dB attenuation difference between the TM and TE modes provides a good indication of the high purity of our graphene sheet and the strong light-matter interaction that has been achieved. We note that the PVB material used here is largely transparent across the transmission window of the silica fibre and thus the device should be operable across the entire telecom band. To test the broadband nature of the device, additional transmission measurements were undertaken at wavelengths spanning 1425–1600 nm, from which it was confirmed that the extinction ratio did not drop below 25 dB in this region see .ave~10 mW the absorption of the TM mode is linear, however, for higher input powers the absorption becomes nonlinear and the transmitted light starts to increase exponentially, eventually reaching a transmittance of 60% for Pave~32 mW. In contrast, the transmission of the TE mode remains linear when the input power is increased up to the maximum available power. This is due to the minimal interaction between the TE mode and the graphene sheet; a phenomenon that forms the basis of the graphene polarizerCharacterization of the nonlinear saturable absorption induced by Pauli blocking was then undertaken using a high power fibre laser operating at 1540 nm, with a duration of 750 fs (FWHM) and a repetition rate of 40 MHz. ave~20 mW, corresponding to a peak power of Pp~720 W) and a weak probe component . The probe was modulated at 100 Hz using an optical chopper connected to a lock-in amplifier to discriminate between the two signals. Polarization controllers were used to ensure that both the pump and probe were aligned to couple into the TM surface wave, and a 10 ps adjustable delay was inserted into the probe’s path to control the overlap between the two pulses. The pump and probe pulses were then recombined using a fused tapered coupler before being connected to the input arm of the device under test. 1~0.1 ps and τ2~0.4 ps, in good agreement with previous reports2 has been found to be directly proportional to the crystal coherence length in the graphene sheet and thus a possible route to increasing the modulator’s intrinsic speed would be to engineer a level of disorder into the lattice.In order to determine the temporal dynamics of the saturable absorption we employed a simple pump-probe modulation scheme, as illustrated in In conclusion, we have designed and experimentally demonstrated a graphene-based all-optical modulator with a high extinction ratio of 9 dB and a speed of 0.5 THz. When compared to previous devices, our method results in an enhanced interaction with the graphene sheet to produce a significant increase in modulation depth, while at the same time ensuring a large decrease in insertion loss. This is best illustrated by applying the figure of merit (FOM) proposed in ref. Standard Corning SMF-28 step-index single-mode fibres with 125 μm diameter cladding, 8.2 μm diameter core, and 0.14 numerical aperture are used for the construction of the devices. An aluminium block was prepared with large-radius curved-sides, a 1 cm long flat-centre and U-shape cross-section groove cut down the middle. The radius of the two curved-side sections was fixed at 30 cm to form an adiabatic transition region and the depth of the groove was ~65 μm to allow polishing to the desired depth. A 3 cm long section of the fibre was stripped of its buffer jacket and bonded into the groove with a wax. The bulk of the top section of the fibre was removed using 3 μm aluminium oxide film, following which it was polished to a surface quality of~1 nm RMS using a proprietary polishing film (UltraTec).2/Ar gas. After that, the temperature was increased to 1000 °C with 6% H2/Ar gas flow of 100 sccm and the chamber pressure maintained at 20 mBar. The Cu foil was annealed at these conditions for 30 min. The graphene growth was performed by flowing 5% CH4/Ar together with 6% H2/Ar gases for 20 min with flow rates of 100 sccm and 210 sccm, respectively. Finally, the CH4/Ar flow was turned off to finish the graphene deposition and the Cu foil was cooled down naturally.A typical CVD system for the fabrication of graphene is shown in the −1 to 2850 cm−1 with a resolution of 0.1 cm−1. The Raman features of mono-layer graphene are the G peak at ~1580 cm−1 and a symmetric 2D peak at ~2700 cm−1 with full-width half maximum (FWHM) of~25 cm−1. The negligible D peak, normally seen in the spectrum near ~1350 cm−1, indicates that high quality  graphene has been produced. In general, the appearance of the D peak indicates the disorder in the carbon lattice such as the domain boundaries, lattice defects or distortion. In addition to the shape of the 2D peak, it is also known that the ratio of I2D/IG can be used to determine the number of graphene layers. The typical I2D/IG ratios of single layer and bilayer exfoliated graphene are ~2–3 and slightly less than 1, respectively. For our as-grown CVD graphene layer shown in The as-grown mono-layer graphene has dimensions of 80 mm × 90 mm, as shown in The optical transmission loss of the device was measured with a 1550 nm diode and the cut-back technique was used to remove extraneous losses. Measurements were undertaken as a function of wavelength using a low power continuous wave Tunics laser as the source and a Newport 818-IR detector. The source used for the high peak power experiments was a OneFive Origami with a bespoke pulse duration of 750 fs FWHM. The carrier dynamics were estimated by comparing the modulated response directly with the pump pulse. As the pump is symmetric, the asymmetry in the tail is attributed to the slow recovery of the carriers. The relaxation times were then determined by fitting the extended tail with a convolution of 2 exponentials.Numerical simulations were undertaken using the COMSOL Multiphysics with the RF module and the LiveLink to MatLab.How to cite this article: Zhang, H. et al. Enhanced all-optical modulation in a graphene-coated fibre with low insertion loss. Sci. Rep.6, 23512; doi: 10.1038/srep23512 (2016).


The questions’ judged answerability level on the two scales was highly correlated. For both scales, consensus questions were rated more answerable than the non-consensus questions, with illusion questions falling in-between. The result for the illusion questions indicates that a feeling of answerability can be created even when it is unlikely that somebody can come up with an answer. The results also showed that individual difference variables influenced the answerability judgments. Higher levels of belief in certainty of knowledge, mankind’s knowledge, and mankind’s efficacy were related to judging the non-consensus questions as more answerable. Participants rating the illusion questions as answerable rated the other answerability questions as more, or equally, answerable compared to the other participants and showed tendencies to prefer a combination of more epistemic default processing and less intellectual processing.Occasionally people may attempt to judge whether a question can be answered today, or if not, if it can be answered in the future. For example, a person may consider whether enough is known about the dangers of living close to a nuclear plant, or to a major electricity cable, for them to be willing to do so, and state-authorities may consider whether questions about the dangers of new technologies have been answered, or in a reasonable future can be, for them to be willing to invest money in research aiming develop such technologies. A total of 476 participants, for each of 22 knowledge questions, either judged whether it was answerable today (current answerability), or judged when it could be answered (future answerability). The knowledge questions varied with respect to the expected consensus concerning their answerability:  In daily life and in science people are sometimes faced with questions that they do not immediately know the answer to. Examples are questions such as “Is it safe to use a cell-phone daily?”, “Can this person be considered guilty beyond a reasonable doubt?”, or “Does this medicine have serious side effects?” Moreover, if a person thinks that a question currently has not been answered, they may consider how long it will take before it will be answered, or if it can be answered at all. For other questions, people may think they know the answer, only to find out that their judgment was premature. Many tragic human catastrophes may, at least in part, have occurred because people misjudged the answerability of important questions, e.g., the Thalidomide catastrophe in the 1950s.answer to mean an answer that is correct and that is provided with good arguments at a relevant level of specification. In this context there are thorny philosophical issues related to, for example, the concepts of truth and knowledge that have been debated by philosophers for centuries. However, this paper does not try to solve such issues. Thus, for example, at a philosophical level, it may presently not be possible to convincingly claim that there is an absolute difference between answerable and non-answerable questions. In spite of this, we note that people, both in science and in everyday life in fact make judgments about when in the future, questions judged not to have been answered, are likely to be so, if ever. The present study investigated people’s subjective judgments of questions’ answerability.The notion that questions can have correct answers is commonly taken for granted in everyday life and in science. In the present research, we use the term Such judgments are important because they may influence other judgments and decisions relevant in everyday life, for example decisions whether to allow new techniques or substances in specific contexts such as in medicines, clothes, foods, or building materials. An example of a future answerability judgment is how many test trials should be made before we can be sure that a new drug is not dangerous to the public? Other contexts where answerability judgments are made in everyday life, including work life, concern allocation of resources to research project applications or to public and other inquiries. For example, if it is reasonable to think that a research project can answer its questions during the time the research money is applied for? As far as we know no research has studied answerability judgments in the broad sense discussed here.Much of previous research on question answerability judgments has been limited to questions where people tend to agree on the answer and has tended to study isolated aspects of the broader answerability question, for example, if I myself or someone else knows the answer to a posed question. Thus, studies of “I know/don’t know” judgments have been made in different fields of psychology. To illustrate, research in forensic psychology has explored participants’ ability to separate out questions on “information not seen” in a video clip e.g., , in geneothers’ knowledge. To illustrate, Research on people’s confidence in their answers to different types of memory questions has in many contexts found a tendency for people to show overconfidence in their responses  have been addressed in educational psychology orientated toward science communication e.g.,  and in rEvidence in risk research shows that differences in cultural values such as hierarchical/egalitarian and individualistic/communitarian may shape individuals’ beliefs about the existence of scientific consensus on such topics as climate change and disposal of nuclear waste . Other rignorance, taken in a broad sense. Researchers have also presented taxonomies of ignorance  and with respect to question answerability (answerability consensus). There are at least three types of possible answerability consensus: whether there is some answer to the question today, whether it can be answered in the future, and about the answerability of specific types of questions. A common conclusion is that people have a tendency to trust socially prevalent understanding e.g., . SociallIn this research we investigated answerability judgments of three types of questions: questions for which we expected a high degree of consensus regarding their answerability (consensus questions), questions for which we expected a low degree of such answerability consensus (non-consensus questions), and questions that may appear answerable but where some information necessary to answer it was missing (illusion questions). However, we do not claim that there is an absolute qualitative difference between these question types, rather the difference may be a question of degree. Consensus and non-consensus questions were used in this research because it is of interest to study the consistency in people’s answerability judgments of questions with different degrees of expected answerability. In addition, we were also interested in studying the degree to which individual difference variables influenced questions with different levels of expected consensus about their answerability (further elaborated below). The illusion questions were included in order to examine the extent to which missing information in the questions might be compensated for by the use of other types of information such as conceptions about the answerability of specific types of questions.We expected that consensus questions would be rated higher in answerability than non-consensus questions (Hypothesis 1). This was partly because we expected that it would be relatively easy for the participants to either provide what they thought was the correct answer to the question (thus showing that is was answerable), or to imagine some easily performed way to get the answer to the question. The illusion questions belonged to geometry and physics and, since we had purposefully eliminated information necessary to answer them, they show similarity to the questions used in the witness psychology and memory studies reviewed above. Moreover, they were designed to appear fairly elementary and computable and we believed many participants (possibly from their school experience) would think that the answer to such elementary computational questions in general is possible to compute. This is in line with current answerability of the question and the other scale to when, if ever, a question can be answered. These two scales were included because it is reasonable to think they are commonly used, explicitly or implicitly, when people judge the answerability of questions in everyday life. In addition, we were interested to compare the answerability levels of the judged questions on the two scales since if the rank order in answerability is stable between the two scales this is an indication of some stability in the processes generating the answerability judgments.Answerability judgments can be made on different types of scales and it is of interest to understand the extent to which the level of the answerability judgment varies as an effect of the used scale. Therefore we compared two kinds of answerability scales with respect to their effect on the level of answerability judgments. One scale related to the per se, may be irrelevant to their realism. Therefore, we also investigated the relation between answerability judgments and measures of individuals’ cognitive and personality properties, henceforth called individual difference variables, that it seems reasonable to believe will be associated with the level of the answerability judgments. In general it would seem that consensus type questions are more likely to be judged by use of quick and fairly automated processes of a System 1 kind  answers may be out of human reach or context dependent . We expeBeliefs about the extent and usefulness of mankind’s knowledge as such also illustrate belief about epistemic issues. Given that more knowledge might be expected to be associated with greater possibility to answer knowledge questions, we hypothesized that belief in a larger body of mankind’s knowledge would be correlated with higher answerability judgments (Hypothesis 4).A further type of belief concerns beliefs about mankind’s effectiveness to reach, for example, epistemic goals , that is, mankind’s efficacy. We expected that participants who believed more in mankind’s efficacy would tend to judge questions as more answerable (Hypothesis 5).EPI-r scale  and preference for a deeper intellectual type of processing measured by EPI-r Intellectual (similar to system 2 processing). We expected that participants with default processing preferences would tend to choose interpretations that come quickly to mind and are easy to handle and therefore would find questions more answerable. Furthermore, we expected that preference for intellectual processing would be associated with lower answerability judgments since participants high in this preference would problematize the possible constructions of answers to questions more than participants low in this preference (Hypothesis 6). Our reasoning here was that people with a higher default processing preference may be more prone to rely on general rules of thumb , while intellectual processing may make it easier to notice that crucial information needed to answer the question may be missing.Shallow or deep processing might influence answerability judgments. Two kinds of processing preferences are measured by the -r scale : prefereOptimism may also affect the level of answerability judgments. People with generalized personal optimism tend to interpret things in a positive way and are less likely to give up . As optiIn total, 476 participants completed the 22 answerability questions in one of the two answerability scale variants . The mean age was 28 years (range 18–78 years). Of the 476 participants, 236  completed the answerability questionnaire using the current answerability scale. The remaining 240 participants  used the future answerability scale. As a reimbursement, participants participated in a lottery for a cinema ticket.The present study followed ethical guidelines in Sweden for survey data. Participants were recruited from a pool of adults that had already actively volunteered and signed up for participation in psychological research and can thus be considered consciously aware of participation in general. They were provided with information about the purpose of the study via e-mail and were told that participation was not mandatory. In the email they were informed that their answers only would be used for research purposes, that they could withdraw at any time. The email also provided relevant contact information. Participants gave their consent by clicking on a survey link. When clicking on the link for participation participants were randomized to four groups. Approximately half of the participants were randomized to each of two scale variants: the current answerability scale and the future answerability scale (described below). In order to control for any ordering effects within each scale variant group the order of the question blocks was altered, constituting two order conditions. In the first order condition (the belief in certainty of knowledge-first condition) the participants answered the belief in certainty of knowledge items first, then the answerability questions, and then three other measures-the LOT-r, EPI-r, and mankind’s efficacy, in a randomized order. In the second order condition (the belief in certainty of knowledge items-last condition) the participants answered the questions in the following order: first the answerability questions, then the three other measures-the LOT-r, EPI-r, and mankind’s efficacy-in a randomized order, and last the belief in certainty of knowledge items. Finally, two questions about mankind’s knowledge and background questions were answered.1 participants answered all the 22 answerability questions and data from that set of people were used for further analysis. Thus, the response rate was 33%.In total 1462 individuals from participant pools at the University of Gothenburg were invited to answer a web-questionnaire. It was not possible to go back to previous pages in the questionnaire to change answers. If participants left a question unanswered, they were kindly reminded but not forced, to complete the question. This rendered 639 answers. Out of these 639, 476Appendix 1). However, at the same time we kept the total number of questions reasonably low in order to achieve a good response rate and an even answer quality throughout the questionnaire . The remaining two questions were illusion questions in which a crucial detail necessary to compute the answer was missing. For example, in the question “How large is the area of an ellipse with a minor axis of 2 cm?” the length of the major axis was absent. Three types of questions were used. There were eight F = 23.45, Bonferroni correction (p < 0.01) which supported the researchers’ intuitions. However, the illusion questions did not differ significantly from the consensus (p = 0.14) nor the non-consensus questions, (p = 0.22).In a pre-study 100 participants from a student pool at the University of Gothenburg rated various aspects of the 22 question-items. Participants estimated the proportion of adult Swedes that would agree that the question is answerable . On average participants judged that 74% of the Swedes would agree that the consensus questions were answerable, but estimated that only 55% of the Swedish population would agree that the non-consensus questions were answerable. Participants further judged 64% of the Swedes would reckon the illusion questions answerable. The difference between consensus and non-consensus questions was significant The questions in the present study were organized in pairs so that questions of different categories were matched with each other. There were two pairs of questions containing one illusion and one consensus questions, six pairs containing one consensus and one non-consensus question, and three pairs containing two non-consensus questions. The just described pairs of answerability questions were presented in an order randomized for each participant.answerability means that the question can be answered on a level that is exact and relevant enough. E.g., for the question “how tall is the world’s smallest living creature ever”, the answer “less than a meter” is not exact enough to be counted as correct.” The instructions are further described in Appendix 2.For both scale variants , the instructions stressed that the judgment task was not to provide the answer as such to the question but to judge the answerability of the question. Moreover, the participants were instructed that “Each screen in the questionnaire presented two questions for which the participants were to give answerability judgments. On the top of each screen was a reminder formulated as follows: “Reminder: for the question to be judged as answerable it is necessary:” (the next three sentences each appeared on its own line) “That at least one person in the world can answer the question. That the answer can be answered correctly and that good arguments for the answer can be provided. That the question can be answered in a sufficiently exact and relevant way.”Figure 1.Two scales were prepared for the answerability judgments. One of the scales, “the current answerability scale” asked the participant to judge the probability that the question could be answered by at least one person now living in the world. The other scale, “the future answerability scale”, more openly directed the judgment to when the question considered can (if ever) be answered. The two scales are shown in If scientists try hard enough they can find the truth to almost everything” and “Scientists can ultimately get to the truth”. Higher values indicate higher belief in certainty of knowledge. The items were rated on a five-point scale, ranging from 1 = Do not agree at all to 5 = Totally agree.Two items from a factor tapping belief in certainty of knowledge in the epistemic beliefs measure presented by Mankind can always manage to solve difficult problems if it tries hard enough”, “Even if hard times threaten mankind, mankind will find ways to reach its goals”, “In unexpected situations, mankind will find ways to act”, and “Even in unexpected situations I believe mankind can cope well”. Items were answered on a five-point scale ranging from 1 = Do not agree, to 5 = Totally agree. Cronbach’s alpha was 0.77.A measure was constructed in order to tap a belief in mankind’s ability to complete tasks and reach goals. The items were similar to self-efficacy items, but instead addressed mankind’s efficacy. The four items were: “How much does mankind know of all there is to know?” and “How much does mankind know of all that is important to know?” Items were answered on a scale ranging from 0 to 100% in intervals of 10. Cronbach’s alpha for the items was 0.66, which although not high can be considered acceptable for research purposes  and intellectual processing . Questions were answered on a five-point Likert-type scale, ranging from 1 = Do not agree to 5 = Agree completely. Cronbach’s alpha was 0.71 for default processing, and 0.81 for intellectual processing.The Epistemic Preference Indicator-Revised  measuresIn uncertain times, I usually expect the best”. The items were answered on a five-point scale ranging from 1 = Do not agree to 5 = Totally agree. Cronbach’s alpha was 0.78.Life orientation test revised measures the degree of optimism regarding oneself and has six items . An itemTable  Since the future answerability scale starts with two categories of a nominal type, these categories were recoded into the same category in order to make the scale more ordinal. Thus, after recoding 1 = I or someone else knows the answer to the question, 2 = Can be answered within 1 year, 3 = Can be answered within 10 years, etc. Medians and interquartile range were used for the future answerability scale.Means, medians, SDs, and interquartile range for the answerability judgments for the three types of questions are shown in Table 1, for the current answerability judgments, consensus questions were perceived to be most answerable (M = 93%), non-consensus questions the least answerable (M = 47%), and illusion questions were rated in between (M = 77%). Figure A1 in Appendix 3 shows that the answerability questions’ mean ratings ranged from almost 100% answerable to approximately 15% answerable.As can be seen in Mdn = 1, “I or someone else knows the answer to the question”) and the non-consensus questions least . Most of the respondents (75th percentile) rated the non-consensus questions to be answered within a maximum of 50 years. The response alternative Can never be answered was chosen 12% of the time.For the future answerability judgments consensus questions and illusion questions were rated most answerable .2 The six individual differences variables were entered as covariates to control for their influence .In order to investigate differences between consensus and non-consensus questions a mixed ANCOVA was conducted with the within-subject factor of question type (consensus vs. non-consensus) and, to control for ordering effects, the between-subject factor F = 35.41, p < 0.001, partial η2 = 0.15. We found no effect of the order factor , F = 0.01, p = 0.942. No interaction effect was found between the question type and order factors, F = 0.25, p = 0.618.Consensus questions were rated as significantly more answerable than non-consensus questions, PS) was used, following PS estimates the probability that a score randomly drawn from population a will be greater than a score randomly drawn from population b.Due to the ordinal properties of the future answerability scale non-parametric tests were used. To estimate the effect sizes the probability of superiority estimator (U-test showed that there were no differences in answerability judgments for the consensus questions as a consequence of whether the belief in certainty of knowledge items were rated before or after the answerability questions (p = 0.957). However, there was a significant difference for non-consensus questions due to rating belief in certainty of knowledge before or after the answerability judgments, U = 8484.50, z = -2.494, p = 0.013. PS = 0.59. Therefore the results for the future answerability of the non-consensus questions were analyzed jointly and separately per order condition and reported when relevant.A Mann–Whitney z = 10.24, p < 0.001, PSdep = 0.74.To investigate differences between future answerability for the consensus and non-consensus questions a Wilcoxon signed rank test was used. The consensus questions were rated as being possible to answer in a nearer future than the non-consensus questions, sr(22) = -0.48, p < 0.03. Thus, on average, the questions considered unlikely to be answered today were considered to be answered in a more distant future. .The median of each question item on the current answerability scale was correlated with the median of each corresponding question item on the future answerability scale. This correlation was significant and very high, Table The means and SDs for the individual difference variables and the current answerability ratings of consensus, non-consensus and illusion questions and Pearson correlations between these variables are shown in r(226) = 0.28, p < 0.001. Also, people who believed more in mankind’s efficacy rated the non-consensus questions as more answerable, r(216) = 0.22, p = 0.001.There were no significant correlations between the individual differences variables and the answerability ratings on the current answerability scale for the consensus questions. However for the non-consensus questions, people that rated a high belief in certainty of knowledge rated these questions as more answerable, F = 5.26, p < 0.001. The regression analysis showed that the individual difference variables explained 13% of the variance in the answerability judgments. Furthermore, belief in certainty of knowledge , mankind’s efficacy  and optimism  yielded significant β-values.In order to explore how much variance in the answerability ratings of the non-consensus questions was explained by the individual difference variables when the current answerability scale was used, a multiple regression with the dependent variable answerability of non-consensus questions and the independent variables belief in certainty of knowledge, EPI-Default, EPI-Intellectual, mankind’s efficacy, optimism and mankind’s knowledge was conducted. The result was significant r(216) = -014, p < 0.047.A negative correlation was found between the answerability ratings of the illusion questions and optimism, thus, the more optimistic people rated illusion questions as less answerable, One hundred and one participants in the current scale condition rated both of the illusion questions as 100% answerable, and were thus “tricked” by the illusion questions. Interestingly, on average these 101 participants also rated each of the other questions higher or equally high in answerability compared to other participants. In order to investigate if epistemic processing preference differed between the tricked and non-tricked participants, a general EPI-score was computed with the formula . Tricked participants did not score significantly higher on the EPI–score.Table The correlations between the future answerability scale and the individual difference measures can be found in p < 0.05) were found between the consensus questions and the individual difference measures for the future answerability scale. As can be seen in Table 3, rating the non-consensus questions to be more answerable in the near future was associated with higher ratings for mankind’s efficacy rs(214) = -0.15, p = 0.028, and mankind’s knowledge rs(214) = -0.15, p = 0.026.No significant correlations (rs(113) = -0.27, p = 0.004. Likewise, the correlation between mankind’s efficacy and the answerability values for the non-consensus questions was more pronounced when belief in certainty of knowledge was judged before answerability judgments, sr(113) = -0.23, p = 0.016.The correlation between mankind’s knowledge and the answerability values for the non-consensus questions was stronger when belief in certainty of knowledge was rated first, Table 3, rating the illusion questions as being more answerable in the near future was associated with higher ratings for mankind’s knowledge rs(214) = -0.14, p = 0.036, and lower EPI-intellectual rating, rs(214) = 0.19, p = 0.005. Thus, higher answerability ratings for the illusion questions were associated with lower values on the EPI-intellectual scale.As can be seen in n = 182) had a significantly lower EPI-score , t(432) = -2.20, p = 0.028, d = -2.20.In total 182 participants claimed the illusion questions could be answered today and were thus tricked by the illusion questions. Comparing the medians, tricked participants judged each of the other questions to be answered at the same time or sooner than non-tricked participants. The tricked participants (This study investigated judgments of current and future answerability of three types of knowledge questions: consensus questions (high level of expected consensus about their answerability), non-consensus questions (lower expected level of consensus about their answerability), and illusion questions . We also investigated whether there was a relationship between various individual difference variables and the level of the answerability judgments.Questions rated low on answerability on the current scale were also rated to be answerable further off in the future. The finding that the level of judged answerability was fairly strongly correlated between the two scales indicates that there is some stability in the processes generating answerability judgments. This result is also in line with the conclusion reached by The consensus questions were rated as having a high level of answerability and were, as expected, judged as more answerable than the non-consensus questions, independent of the scale used. A possible explanation for the high ratings of the consensus questions is that fairly automated memory processes more often quickly identified a correct answer or classified the consensus questions as being a type of question that could be known by myself or by others. This explanation coheres with research on “don’t know” judgments which shows that spontaneous quick processes may quickly contribute to the assessment of many questions e.g., . ResultsThe non-consensus questions were given the lowest answerability ratings of the three question types. In line with the considerations above, the answerability ratings for these questions may have been more dependent on elaborated and deliberative thinking, compared to the consensus questions. For example, it is likely that there was less experienced consensus about a possible answer to many of these questions and that for this reason the advice offered from socially prevalent knowledge compare  may haveper se. Interestingly, participants who failed to notice the missing information in the illusion questions also rated other questions either higher or equally high in answerability.Many participants rated the illusion questions as answerable today even though crucial information was missing. The results for the illusion questions indicate that a “feeling of others knowing” can be created even when it is unlikely that somebody can come up with an answer. The participants who were tricked by the illusion questions showed tendencies to have an epistemic preference for higher default processing in combination with lower intellectual processing. High answerability judgments for the illusion questions may therefore possibly be explained by shallow processing based on general beliefs , in contOverall, the individual difference variables all showed acceptable or satisfactory Cronbach’s alpha values and were moderately related to answerability judgments. In line with our hypothesis, when an effect was found it was related to the answerability of non-consensus questions, not to the consensus questions. However, it should be noted that the weaker correlations for the consensus questions may also be due to their lower variability, compared with that of the non-consensus questions and this issue should be further explored in future research.Together the individual difference variables explained 13% of the variance of the answerability judgments for non-consensus questions when the current scale was used. This can be seen as an irrelevant influence on the level of the answerability judgments in the sense that variance in individual difference variables is not usually considered likely to contribute to better quality in judgments, that is, more realistic values. Future research should investigate if there are specific levels of some individual difference variables that are beneficial for producing realistic answerability judgments. Generally speaking, in important applied contexts it may be worthwhile to develop approaches that can help to decrease the negative influence of individual difference variables.It is also noteworthy that the participants who believed more in certainty of knowledge also rated the more challenging questions (the non-consensus questions) as more answerable, especially for the current scale, providing some support for our hypothesis. They also tended to believe more in mankind’s knowledge  and especially to believe more in mankind’s efficacy with respect to solving difficult problems and troubles. These associations may also have contributed to the tendency for participants who believed more in mankind’s knowledge and efficacy to give higher answerability ratings. Future research should investigate whether people who believe more in certainty of knowledge and mankind’s efficacy differ from other people in the realism of their answerability judgments. For example, do such people, when they consider real-life complex issues, have a tendency to underestimate the number of variables relevant to consider or the complexity of the possible interactions between variables?When it comes to epistemic preferences, we expected that preference for default processing would be associated with higher answerability judgments and intellectual processing with lower answerability judgments. Although the earlier mentioned result showed that participants high in default processing and low in intellectual processing were tricked more by the illusion questions, only a weak correlation was found between intellectual processing and low answerability for the illusion questions when using the future scale. Although it was small, this correlation supports our hypothesis. Since people high in intellectual processing enjoy and take time to think about problems , it is llower answerability ratings on the non-consensus and the illusion questions for the current answerability scale. According to explanatory style or dispositional optimism. Explanatory style relates to how the individual tends to explain good or bad outcomes and may be less relevant to the present study. Dispositional optimism means a tendency to expect good things and few bad things to happen in the future, to believe that one can reach one’s goals  speaks against this interpretation, although this correlation, in spite of it being significant, was relatively low. It would seem more likely that the lack of associations between the consensus questions and the individual difference variables is a true effect in the sense that individual difference variables, for reasons discussed above, may have had less influence on the judgments of these questions, although future research should examine this issue further.As already noted, the results showed that answerability judgments of the consensus questions were not appreciably influenced by the individual difference variables. This could be due to a ceiling effect since the consensus questions received very high ratings, limiting the spread of their answerability ratings. However, the fact that the answerability ratings for the two types of questions were significantly correlated  can be argued to have a fairly positive attitude toward research and science. Future research should test if our results generalize to more representative groups of people and to people faced with uncertain but important questions, for example, researchers and politicians. Furthermore, future research should preferably use a larger number of answerability questions, especially a larger number of illusion questions.Finally, future research should also investigate people’s answerability judgments of other types of questions than in the present study. Examples are questions relating to current controversies in science and questions more clearly related to social life, such as questions whether a suspect can be considered guilty “beyond reasonable doubt” (see e.g., BK has with CMA had the main responsibility for data-collection, analysis, conclusions and creation of the manuscript. BK and SB have performed approximately half of the statistical analyses each. Furthermore, SB has actively supported the development of the study and has several times reviewed the paper and contributed to the Introduction and the Discussion with formulations and interpretations of theories.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


In this review we highlight recent theoretical and experimental work on sublattice asymmetric doping of impurities in graphene, with a focus on substitutional nitrogen dopants. It is well known that one current limitation of graphene in regards to its use in electronics is that in its ordinary state it exhibits no band gap. By doping one of its two sublattices preferentially it is possible to not only open such a gap, which can furthermore be tuned through control of the dopant concentration, but in theory produce quasi-ballistic transport of electrons in the undoped sublattice, both important qualities for any graphene device to be used competetively in future technology. We outline current experimental techniques for synthesis of such graphene monolayers and detail theoretical efforts to explain the mechanisms responsible for the effect, before suggesting future research directions in this nascent field. With its excellent transport properties and low dimensionality, graphene, an atomically thin layer of Carbon atoms bonded together in a hexagonal lattice, initially seems a strong candidate for use in many future commercial applications such as ultra high-speed transistors, integrated circuits and other novel devices –3. One o4–107 and a band gap of at least 340 meV whilst maintaining high carrier mobility [Although several methods exist to induce a band gap, for example 1D quantum confinement by construction of graphene nanoribbons (GNRs) , stackinmobility ,13–14.Alteration of the crystal structure through the introduction of foreign dopants is one of the more realistic avenues of approach in realising this goal. Atomic dopants like boron (B) or nitrogen (N) are a similar size to carbon and can be introduced easily in a variety of graphene growth processes, typically replacing carbon sites and forming substitutional impurities in the lattice, positively (p-) and negatively (n-) doping the system for B and N dopants respectively . Early tWhilst these findings are certainly interesting, their scalability, and hence commercial application, is prohibited by the standard of precision that must be met in order to produce such materials. Circumventing these problems using nitrogen doped graphene has only come about relatively recently which we detail in the following section.3 as a precursor, arc discharge [Exploiting the effects of nitrogen dopants on the transport properties of graphene has been an interesting experimental research topic for the last 5 years , wherebyischarge , embeddeischarge , ion impischarge –26, ammoischarge  or nitroischarge –29 treatischarge  and withischarge . Althougischarge  and singischarge . Using nischarge  and by iischarge . Boron discharge –35. Thisischarge –37, whic3) naturally incorporates nitrogen atoms as substitutional so-called ’graphitic’ dopants , followed by a short investigation on the transport properties of the resulting graphene. Their experimental observation of same sublattice segregation, at least on local scales, was noted as a curiosity but was not discussed in depth. A key finding by the researchers was that by varying the ammonia precursor concentration they could adjust the resulting embedded dopant concentration. Further theoretical work confirmed that a tunable band gap would be obtainable using this method , and alo2AA pairs [2AA to single N increasing with reaction time. The samples had a typical concentration of around 0.25% nitrogen dopants.Shortly after this work a more focussed investigation was undertaken by Lv et al. . They weAA pairs   substrate and the boron impurity, in contrast to a very weak interaction with the substrate for nitrogen impurities [More recently the addition of boron dopants into the lattice and their effects have been studied  using hipurities .5H5N) precursor for the nitrogen and graphene instead of the conventional ammonia/methane mix. The most recent and thorough study of asymmetric nitrogen dopants in graphene is by Zabet-Khosousi et al.  who agaiThe common elements of all the aforementioned experimental reports are that they all use a Cu(111) substrate, all have reaction times exceeding 10 min in a temperature range of 800–900 °C, and all have used either ammonia or pyridine precursors to achieve concentrations of up to 0.3%. A review of other methods for N-doped graphene synthesis finds no mention of sublattice asymmetry –30, it iIt is clear that any degree of asymmetry between the two equivalent sublattices is the result of a symmetry breaking operation. Current theoretical attempts to explain the sublattice asymmetry in the nitrogen doping seen in the experiments discussed in the previous section suggest that the effect comes from either the energetically preferable positioning of nitrogen on the graphene edge during the growth process –42, wherThe edge growth model suggests that during the growth phase the most energetically favourable position for a nitrogen dopant being incorporated into a graphene edge would be that which leads to a same sublattice configuration for all impurities in a domain. Through density functional theory (DFT) calculations involving a graphene nanoribbon on a Cu(111) substrate, aiming to reproduce experimental conditions, a thorough investigation into the energetic favourable position of single graphitic nitrogens in the GNR was undertaken and the energetic difference between placing the nitrogen at one edge site over another on the opposite sublattice was found to be a substantial 1.3 eV. One drawback of this method is that one would expect therefore that the clearly defined segregation domains seen experimentally (see 2AB. This contradicts the experimental reports of Lv et al. [2AA defects in their samples. A simplistic tight binding approach predicts that two identical impurities in close proximity to one another would indeed have an energetic minimum when both occupy the same sublattice [2AB′ (see 2AA. This appears to be in disagreement with experiments where N2AA is more commonly found than N2AB′. As a final note their calculations have also shown that two N2AA pairs have a lower energy when they share the same sublattice, however further studies have shown that the overall energy change resulting from an N2AA pair in the sheet is very high [2AA in nitrogen ion implanted graphene [In-depth DFT calculations by Hou et al.  found thv et al.  who founblattice , however2AB′ see , approxiery high . It is pgraphene  indicateThe earliest attempts to study nitrogen dopants and their effect on the graphene electronic properties were purely theoretical. Beginning with impurity superlattices, this research preceded the experimental realistation of nitrogen doped graphene. By introducing a controlled periodic arrangement of boron and nitrogen impurities a band gap was seen to open , and altEven with a 4:1 doping ratio between sublattices, the band gap, although smaller, was shown to still exist. This is promising for scaleability where perfect asymmetric doping may not always be realizable. Beyond the realization of quasi-ballistic electron transport, sublattice segregated systems can also be used to induce magnetism ,48–50 anMuch work has been done studying how the placement of dopants affects the properties of nanoribbons. DFT approaches, using a periodic system of dopants –54, and It should also be noted that that symmetry breaking in nanoribbons occurs via edge effects and also results in a favourable sublattice , howeverAt the time of writing, the synthesis of sublattice asymmetric graphene is only just now becoming practical. There are still many unanswered questions and the most important ones we outline in this section.The natural question to ask is if this asymmetry is particular to nitrogen only, or if it can be found with other dopants. Theoretical findings in the past have shown that such an effect can be expected with a dilute concentration of certain adsorbates , and indThe experimental realisation of spin-polarized transport should also be pursued, and could spark additional interest in this research area beyond quasi-ballistic transport. Investigation of the effects of strain on such a system is difficult due to the technicalities of the CVD method, but could be explored using adsorbates instead of substitutions or by incorporation of the strain in to the nitrogen ion bombardement and annealing procedure discussed earlier. Another open question is if a critical concentration of dopants exists, as mentioned in the theory section, which would limit the available bandgap below the threshold needed for future use in GFET devices. Currently all experimental reports on sublattice asymmetry have very low concentrations of dopants around 0.3%, so it should be feasible to test the existence of a critical concentration of using available methods . ConsequThis paper reviews the current state of experimental and theoretical research in sublattice asymmetric nitrogen doped graphene. Not only are such systems now able to be synthesised in the lab, we have seen that this area shows promise attaining graphene-based FET devices due to the opening of a bandgap whilst maintaining the excellent transport properties of graphene, something which is not realisable in graphene with no sublattice imbalance in dopant distribution. While there are still many open questions in the field these should be answerable within the scope of current techniques.


Previous studies have presented algorithms for detection of turns during gait using wearable sensors, but those algorithms were not built for real-time use. This paper therefore investigates the optimal approach for real-time detection of planned turns during gait using wearable inertial measurement units. Several different sensor positions  and three different detection criteria  are compared with regard to their ability to correctly detect turn onset. Furthermore, the different sensor positions are compared with regard to their ability to predict the turn direction and amplitude. The evaluation was performed on ten healthy subjects who performed left/right turns at three amplitudes . Results showed that turn onset can be most accurately detected with sensors on the back and using a combination of orientation and angular velocity. The same setup also gives the best prediction of turn direction and amplitude. Preliminary measurements with a single amputee were also performed and highlighted important differences such as slower turning that need to be taken into account. For example, a powered prosthesis can provide different types of support depending on whether the user wishes to walk, stand in place or sit down . While tMost gait analysis studies with wearable sensors have focused on steady-state walking, where they extract parameters such as stride length  and deteMost automated gait analysis algorithms treat gait as taking place only in the sagittal plane of the body, allowing considerably simplified calculations ,12. HoweNumerous personal navigation algorithms have been developed for wearable sensors to track and reconstruct walking trajectories over longer distances ,17. Whilet al.  s,-Percentage of correctly classified amplitudes at T = ONSETT +  s.Direction and amplitude classification were evaluated as:These were calculated at different times since we assume that the turn direction and amplitude are easier to identify later in the turn. They were calculated only for trials where a turn is detected correctly (within 500 ms of the reference).2.6.Since we lack access to amputee subjects, the pilot test with the amputee was performed at a different location by the same experimenters on the same day as a larger set of measurements for an unrelated gait analysis study. The amputee wore IMUs on the lower back, thighs, shanks and feet like the unimpaired subjects, but upper back and head IMUs were omitted for logistical reasons. Furthermore, due to time constraints, only 12 trials were performed: two for each turn direction (left/right) and amplitude (22/45/90 degrees).Since there were not enough trials to perform within-subject crossvalidation with the amputee, only a form of subject-independent crossvalidation was performed: the onset detection and direction/amplitude classification algorithms were trained using data from all healthy subjects and tested on the 12 amputee trials. Results are given in Section 3.3.3.The total duration of one trial across all ten unimpaired subjects was 16.4 s ± 2.2 s (mean ± standard deviation). Subjects began walking 8.3 s ± 2.3 s after the start of the trial. In trials where a turn occurred, turn onset was 10.2 s ± 2.3 s after the start of the trial. Examples of the upper back gyroscope signal and angle are shown for unimpaired subjects in 3.1.In this section, we present onset detection results for the three different criteria: orientation threshold only , angularComparing the results in gyr_thresh and angle_thresh to detect onset, the optimal subject-independent thresholds are gyr_thresh = 58°/s and angle_thresh = 23°. In the within-subject case, the optimal gyr_thresh varies (among subjects) from 25°/s to 80°/s while optimal angle_thresh varies from 22 to 30°. Similar values (subject-independent optimum: gyr_thresh = 56°/s and angle_thresh = 23°) were obtained for the lower back IMU. The intersubject variation in optimal gyr_thresh is likely due to subjects turning at different speeds.If we use the upper back IMU with both gyr_thresh and angle_thresh to detect onset, the majority of detection errors in within-subject crossvalidation are due to 22-degree turns: out of all premature/late detections and false negatives, 72% occur with 22-degree turns, 20% with 45-degree turns, and only 8% with 90-degree turns. Interestingly, this is not the case in subject-independent crossvalidation: there, out of all premature/late detections and false negatives, 31% occur with 22-degree turns, 39% with 45-degree turns and 30% with 90-degree turns.Furthermore, if we use the upper back IMU with both For the combination of both thresholds (orientation and angular velocity), we additionally evaluated the onset detection for the special case where only larger turns are considered . It can 3.2.As mentioned, turn direction and amplitude classification was evaluated only for trials where turn onset was correctly detected by the IMU. Classification accuracy is shown in In general, the head IMU provides the most reliable direction and amplitude information in within-subject crossvalidation, followed by the two IMUs on the back. In subject-independent crossvalidation, the IMUs on the back are the most accurate. Though not reported in detail, the majority of misclassifications occur with 22- and 45-degree turns. For example, with the upper back IMU, 90-degree turns represent less than 20% of all misclassifications at any given time for both crossvalidation types. At 0.3 s since detected turn onset (or later), 90-degree turns represent less than 10% of all misclassifications for both crossvalidation types.vs. both thresholds), and we have only reported direction and amplitude classification results for the best case when both onset thresholds are used.Care should be taken when comparing turn direction and amplitude classification results from the different IMUs. Since classification is performed only for trials where the turn onset is detected correctly, it is not possible to directly compare e.g., upper back results (where over 85% of turn onsets are correctly detected) with foot results (where less than 75% of onsets are correctly detected). It is therefore also difficult to compare results between different onset detection criteria  However, turn amplitude classification was largely unsuccessful: at the time of detected turn onset, amplitude was correctly classified in 4 of 9 trials using the lower back IMU and 3 of 7 trials using the thigh IMU. 0.5 s after detected turn onset, amplitude was correctly classified in 5 of 9 trials using the lower back IMU and 4 of 7 trials using the thigh IMU.4.4.1.Results from unimpaired subjects indicate that, whatever the onset detection criterion, the best results can be obtained using an IMU placed on the upper or lower back. While there are only small and inconsistent differences between the two IMUs on the back, the IMUs on the legs consistently produce worse onset detection results as well as lower percentages of correctly classified turn directions and amplitudes. The cause for this is not clear, but we believe that it is due to two reasons. The first reason is the top-down turning strategy, where the upper body generally turns earlier than the lower body ,22. The The head IMU is a special case. The majority of subjects look at the endpoint for the current trial even before starting to walk, and vary between looking straight ahead or looking at the endpoint. Thus, while information about the walking direction is visible in the signals from the head IMU, it cannot be used to predict when the turn itself will occur.We can conclude that, if we wish to detect turn onset rapidly with a single IMU, it should be placed on the trunk rather than the legs. This importance of the upper body during gait is not new and has been previously emphasized in the context of lower limb exoskeletons ,23, but 4.2.For unimpaired subjects, the orientation threshold can be used to correctly detect about 75% of turns using the upper and lower back IMUs in within-subject crossvalidation. The angular velocity threshold correctly detects slightly over 80% of turns using the upper and lower back IMUs in within-subject crossvalidation, but also produces more false positives. Combining both thresholds for onset detection produces the best results, with the highest percentage of correct detections and a low percentage of false positives . DependiThe amputee, who turns more slowly, exhibits lower angular velocity peaks compared to healthy subjects. This suggests that the angular velocity threshold may be less useful in both amputees and in elderly unimpaired subjects who would also turn more slowly than young subjects. However, the combination of orientation and angular velocity thresholds on the lower back was still able to achieve a reasonable percentage of correctly detected onsets.It should be noted that, although combining the two thresholds allows turn onset to be detected accurately with respect to an optical reference, this is only important if we are interested in real-time detection where smaller detection delays give an assistive device more time to react. For annotation of offline data, an orientation threshold is sufficient, as has been shown in previous work ,19. Neit4.3.The best results were obtained in within-subject crossvalidation, where the algorithms are trained individually for each subject. This implies that, for any online application, the algorithms should also first be trained individually for each subject. Depending on how robust we wish the trained algorithms to be, this training process may be time-consuming as trials of different speeds and turn amplitudes are collected in different conditions. Our own measurement protocol required over 30 minutes for each subject and was conducted at a single walking speed.et al. [The main foreseen application of the algorithm is in assistive devices such as powered prostheses. Such a device would not be used by many people, but even training for one person would be time-consuming. The best approach may be a combination of subject-independent and subject-specific training. For example, the hand prosthesis control approach of Tommasi et al.  starts w4.4.The cost function used to train the onset detection algorithm (Section 2.4.1) represents a weakness of the study, as it is somewhat arbitrary. An intuitive alternative would have been to replace it with a more complex way of finding a threshold. We used more complex methods for gait event detection in our previous studies ,11 but wThe manual approach for onset detection used by the human experts may also bias the algorithm’s results. For example, since the Optotrak markers are placed on the head and trunk rather than the legs, the expert-defined reference onset is more likely to match the lower and upper back IMUs since they are also placed on the legs. We believe that the delays in turn onset between the trunk and legs are much smaller than the 500-ms interval for correct detection, and that this issue therefore did not have a major effect, but it should nonetheless be mentioned.Within the cost function, some parameters have been chosen ad-hoc based on our own experiences and previous studies. For example, the 500-ms criterion for error computation was chosen based on two things. First, previous studies in arm prosthetics have shown that delays over 300 ms are unacceptable for real-time control [4.5.The main weakness of the presented approach is the limited evaluation, which was done mostly with relatively young, healthy subjects and only a single amputee. Preliminary results from the amputee suggest that turning behavior is not entirely dissimilar in amputees compared to healthy subjects, and onset detection rules can be transferred from healthy subjects to amputees to some degree. However, the amputee does turn more slowly, with lower angular velocity peaks. This suggests that an angular-velocity-based threshold for onset detection may be less useful for amputees and elderly subjects. The slower turning speed may also be the reason why turn amplitude classification was not successful in the amputee.Furthermore, in a few amputee trials, the turn onset is visible essentially simultaneously for all IMUs see . These tIn general, elderly subjects are known to exhibit different turning behavior ,22. Addi4.6.Though our algorithm has not been tested with an assistive device, we can briefly describe the expected application. While the wearer walks with the assistive device (powered prosthesis or orthosis), the algorithm constantly checks whether a turn onset is occurring. Once the onset is detected, the algorithm should immediately notify the device that a turn is occurring, causing it to switch from assisting forward gait to ensuring stability during the turn, similarly to a stumble detection algorithm . The dev5.This paper builds on previous turn detection algorithms by presenting an optimal setup for real-time turn onset detection during gait using IMUs. Based on our measurements, two conclusions should be drawn. First, IMUs should be placed on the trunk (upper or lower back) rather than the legs for most accurate turn onset detection. Second, a combination of thresholds on orientation and angular velocity provides better results than a single threshold (orientation or angular velocity). Once turn onset has been detected, turn direction can also be easily detected from the IMUs on the back, though amplitude is more difficult to detect. Subject-specific detection thresholds provide better results, though they may be time-consuming to train.The turn detection algorithm is foreseen for use with assistive devices that need to react to a turn as quickly as possible. Using our cost function, the detection thresholds can be adapted so as to, for example, minimize false positives or false negatives. However, our preliminary test with the amputee highlighted important differences between unimpaired and impaired subjects, such as the slower turning speed. Therefore, further evaluations with target populations and with more difficult situations  are required to determine the extent to which our findings can be generalized.


The timed up and go test (TUG) is a functional test which is increasingly used to evaluate patients with stroke. The outcome measured is usually global TUG performance-time. Assessment of spatiotemporal and kinematic parameters during the Oriented gait and Turn sub-tasks of the TUG would provide a better understanding of the mechanisms underlying patients’ performance and therefore may help to guide rehabilitation. The aim of this study was thus to determine the spatiotemporal and kinematic parameters which were most related to the walking and turning sub-tasks of TUG performance in stroke patients.29 stroke patients carried out the TUG test which was recorded using an optoelectronic system in two conditions: spontaneous and standardized condition (standardized foot position and instructed to turn towards the paretic side). They also underwent a clinical assessment. Stepwise regression was used to determine the parameters most related to Oriented gait and Turn sub-tasks. Relationships between explanatory parameters of Oriented gait and Turn performance and clinical scales were evaluated using Spearman correlations.Step length and cadence explained 82% to 95% of the variance for the walking sub-tasks in both conditions. Percentage single support phase and contralateral swing phase (depending on the condition) respectively explained 27% and 56% of the variance during the turning sub-task in the spontaneous and standardized conditions.Step length, cadence, percentage of paretic single support phase and non-paretic swing phase, as well as dynamic stability were the main parameters related to TUG performance and they should be targeted in rehabilitation. Patients with stroke-related hemiparesis frequently have impaired balance and gait, limiting daily life activities. The improvement of locomotor skills is therefore a major aim of stroke rehabilitation  and an aMotion analysis would be a pertinent method to investigate biomechanical aspects of the TUG. The use of instrumental biomechanical tools to assess functional tasks has increased over the past few years. Galli et al 2008) and Lecours et al (2008) both quantified kinematics and kinetics during sit to stand in subjects with stroke and healthy subjects , 7. Dion and LecoThree-dimensional analysis using an optoelectronic system is the current gold standard for the biomechanical assessment of patients with gait abnormalities . This meThe aim of this study was thus to determine which spatio-temporal and/or kinematic parameters would be the most related to performance in Oriented gait and Turn sub-tasks of the TUG test (time to perform the sub-task) in stroke patients. We hypothesized that the percentage of single support phase and peak hip extension on the paretic side would be particularly related to the performance of Oriented gait and Turn sub-tasks of the TUG. The percentage of single support phase during gait has been shown to predict the time to perform the entire TUG test and peak hip extension has been shown to be associated with gait speed , 15.Twenty nine participants with chronic hemiparesis were included  . The inc3D-TUG analysis was carried out using an optoelectronic motion capture system . Markers were fixed to specific bony landmarks on both sides of the body according to the Helen Hayes marker set , 17: theIt has been shown that seat height, foot position and turning direction influence the sit to stand movements and TUG performance in healthy and stroke subjects , 22, 23.Marker trajectories were recorded using 8 infrared cameras and filtered using a low-pass Butterworth filter with a cut off frequency of 6 Hz . AnatomiThe data were then exported to Matlab  for calculation of the biomechanical parameters in each sub-task.Time taken to perform each sub-task, which corresponded to TUG performance.Spatiotemporal parameters: cadence, width, and step length and percentage of single support phase (%SSP) and swing phase (%SP) for each limb.Kinematic parameters: peak flexion and extension of the hip, knee and ankle on the paretic and non-paretic sides. For the ankle, maximal dorsiflexion was also calculated during swing phase.The parameters analyzed were:Spasticity of the whole quadriceps, rectus femoris (one head of the quadriceps), hamstring and triceps surae was evaluated with the Modified Ashworth Scale (MAS) . Strengt0+ b1X1+ b2X2+….+ bpXp where Y is the explanatory value, X1 through Xp are p distinct explanatory variables, b0 is the value of Y when all the independent variables (X1 through Xp) are equal to zero and b1 to bp are the estimated regression coefficients. Each regression coefficient represents the change in Y relative to a one unit change in the respective independent variable.Descriptive statistics including means and standard deviations were calculated for each parameter and Oriented gait  and Turn in both conditions (Spont and Stand). To identify the spatiotemporal and kinematic parameters which were the most related to Oriented gait (Go and Return) and Turn performance, a stepwise multiple regression analysis with forward selection was used. The number of variables included in the stepwise analysis has to be small compared to the number of subjects . FirstlyA Spearman’s test was then used to evaluate correlations between variables found to explain TUG performance from the stepwise analysis and clinical tests since clinical data were not continuous (level of significance p<0.05).Results of the Oriented gait (Go and Return) and Turn performance and spatiotemporal and kinematic parameters for each sub-task and both conditions (Spont and Stand) are presented in In Spont: 4.83(1.18)s for Go, 2.98 (0.73)s for Turn and 4.23(1.02)s for Return;In Stand: 4.56(1.01)s for Go, 3.16(0.84)s for Turn and 3.81(0.91)s for Return.In Spont, sixteen participants turned towards the paretic side, 10 towards the non-paretic side and 3 changed turn direction within the 3 trials.Median summed spasticity score was 4±3.6, median summed MRC score was 23±5.7, median pressure score on the sole of the foot was 1±0.5 and median proprioception score for the toe was 2±1.1 (both assessed with Nottingham Sensory Assessment). Eighteen subjects had claw toe in standing. Mean BBS score was 50.5±2.3, mean ABC score was 76.3±12.9. The median rate of falls was 1±0.7 and median fear of falling score was 2±3.2.Go: step length, %SP and %SSP on both sides and cadence and peak hip flexion on the paretic side were significantly negatively correlated with Go performance.Turn: paretic step length and %SP and non-paretic %SSP were significantly negatively correlated with Turn performance.Return: step length and %SSP on both limbs, non-paretic %SP and cadence were significantly negatively correlated with Return performance.Go: step length, %SP and %SSP on both sides and cadence were significantly negatively correlated with Go performance.Turn: %SP and %SSP on both sides and paretic step length and paretic peak knee extension were significantly negatively correlated with Turn performance.Return: step length, %SP and %SSP on both sides and cadence were significantly negatively correlated with Return performance.Step length on both sides and cadence were selected for Go, explaining 93% of the variance of Go performance.For Turn, non-paretic %SSPwas the only variable selected, explaining 27% of the variance of Turn performance.Turn performance = 6.8 − 0.08 non - paretic %SSPFor Return, step length on both sides and cadence were selected, explaining 82% of the variance of Return performance.➢ For Go, step length on both sides and cadence were selected, explaining 95% of the variance of Go performance.For Turn, non-paretic %SPand paretic %SSP were selected, explaining 56% of the variance of Turn performance.For Return, non-paretic %SP, cadence and step length on both sides were selected, explaining 87% of the variance of Return performance.Results of the stepwise analysis for both conditions are summarized in The BBS score was positively related to most parameters. MRC, fall frequency, fear of falling and MAS were only related to a few parameters. No correlations were found between the presence of claw toe, foot sole pressure score, toe proprioception score and ABC score and any biomechanical parameter.To the best of our knowledge, the present study is the first to use 3D motion analysis to investigate spatiotemporal and kinematic parameters during Oriented gait and Turn sub-tasks of the TUG test in order to provide a deeper understanding of locomotor control in patients with stroke. The aim of this study was to determine the spatio-temporal and kinematic parameters which relate to performance in Oriented gait and Turn sub-tasks of the TUG in stroke patients. The results showed that in the spontaneous condition, step length on both sides and cadence best explained Go and Return performance, whereas percentage non-paretic SSP best explained Turn. In the standardized condition, the same parameters were selected in the stepwise analysis for Go and Return, and in addition, percentage non-paretic SP was selected in Turn and Return and percentage paretic SSP in Turn. Our hypothesis is partly confirmed since the percentage of single support phase was related to timed Turn performance but peak hip extension was not.It is not surprising that step length and cadence explained performance in the walking sub-tasks since gait speed is the product of step length and cadence. Correlations have previously been found between total TUG time and gait speed . ImproveNone of the kinematic parameters studied explained Oriented gait and Turn performance. This corroborates with a previous study which highlighted that kinematic parameters during conventional gait analysis were not predictive of the time to perform the entire TUG test . Since iSurprisingly, no correlations were found between MRC scores and the biomechanical parameters which were related to the Go and Return sub-tasks. Previous studies have shown that the best predictors of gait performance are strength of the paretic lower limb and balance in stroke patients . AnotherPercentage SSP appears to play an important role in the Turn sub-task although the limb (paretic or non-paretic) differed according to the condition. This corroboratesa previous study in our group showing that paretic %SSP assessed during conventional gait analysis is predictive of total TUG performance time in stroke patients . In stroTo summarize, these results indicate that the walking sub-tasks of the TUG test which require a forward progression of the body are mainly affected by step length and cadence, while the turning sub-task of the TUG requires balance control which is related to the percentage of the gait cycle spent in stance phase. However, the percentage variance explained was high for the Go and Return sub-tasks (between 82% and 95%) and moderate for the Turn (27% and 56%) in both conditions. Both conditions (Spont and Stand) lead to the same explanatory parameters for walking sub-tasks (step length and cadence). In contrast, the Stand condition better explained the variance for the Turn sub-task, we therefore suggest that the standardized condition is more pertinent for the biomechanical assessment of Oriented gait and Turn sub-tasks of TUG performance. Confidence in carrying out activities (ABC score) was surprisingly not related to any of the biomechanical explanatory parameters. Oriented gait and Turn sub-tasks of TUG test appears thus more related to a global fear of falling than confidence to carry out specific activities.The sample of participants in the present study was a little younger (54.2±12.2 years) than other studies in the literature. However, it is unlikely that this would have influenced the results since Oriented gait and Turn sub-tasks of TUG performance was similar to that reported by Faria et al who found a time of 10.36s for the walking sub-tasks (summed) and 3.18s for the turning sub-task in patients with chronic stroke (mean age 59.12±2.28y) . SimilarThe differences found between the Spont and Stand conditions may be due to the fact that the Spont condition was always performed first. However, for the spontaneous condition to reflect spontaneous performance, it was essential for it to be carried out first. A similar methodology was used in another study .This study investigated spatiotemporal and kinematic parameters in Oriented gait and Turn sub-tasks of the TUG test in stroke patients. The results showed that step length and cadence explained most of the variance in the performance of the walking sub-tasks and, %SSP and %SP explained the turning sub-task. Balance capacity (assessed with BBS) and fear of falling were associated with the biomechanical parameters which explained performance in both the walking and the turning sub-tasks whereas spasticity, strength, sensation and proprioception were not, or only very slightly, related. It can thus be concluded that dynamic stability is the main capacity required to perform the walking and turning sub-tasks of the TUG. The results of the Spont and Stand conditions differed slightly, probably due to the different directions of the turn. More variance was explained in the standardized condition and therefore we suggest that this condition should be used to evaluate Oriented gait and Turn sub-tasks of TUG performance. This study demonstrated that biomechanical analysis of the Oriented gait and Turn sub-tasks of the TUG is useful to increase understanding of gait abnormalities. This is relevant for rehabilitation since the tasks evaluated by the TUG are highly functional and are carried out frequently throughout the day, however are rarely assessed using accurate tools. This analysis assesses balance capacity during gait, either for monitoring purposes or to evaluate the effects of treatment . Moreover, the results of this assessment can be used to optimize rehabilitation, for example, to improve performance during the gait sub-tasks, rehabilitation should focus on increasing cadence and step length, whereas to improve the performance on the turning sub-task, balance capacity and particularly single support phase on the paretic side should be specifically trained.


In this perspective article, we consider the relationship between experience sharing and turn-taking. There is much evidence suggesting that human social interaction is permeated by two temporal organizations: (1) the sequential framework of turn-taking and (2) the concurrent framework of emotional reciprocity. From this perspective, we introduce two alternative hypotheses about how the relationship between experience sharing and turn-taking could be viewed. According to the first hypothesis, the home environment of experience sharing is in the concurrent framework of emotional reciprocity, while the motivation to share experiences is in tension with the sequential framework of turn-taking. According to the second hypothesis, people’s inclination to coordinate their actions in terms of turn-taking is motivated precisely by their propensity to share experiences. We consider theoretical and empirical ideas in favor of both of these hypotheses and discuss their implications for future research. In recent years, there has been an increasing number of conversation analytic studies explicating the social organization of, and the highly ordered interactional tasks performed by, emotional expressions in social interaction e.g., . This pesequential framework of turn-taking. It denotes not only the temporal but also the conditional relationship between participants’ interactional moves.Many naturally occurring interactions call for individuals to coordinate their actions in terms of turn-taking. This happens especially in the context of language use: the principle of one participant talking at a time  allows hconcurrent framework of emotional reciprocity. The literature on “emotional contagion” suggests that humans have an automatic tendency to mimick other people’s non-verbal emotional expressions, which affects the emotional experience of the mimicking person  telling lines 1–6) both participants are looking down with straight faces (Frame 1). At the end of the telling, however, they establish mutual gaze and the teller (B) adopts a smiling face (Frame 2). After a gap (line 7), the recipient (A) reciprocates the smile and raises her brows (Frame 3), simultaneously producing an animated verbal response of “ritualized disbelief” , they ma–6 both pThe idea of experience sharing being in tension with the sequential temporality of turn-taking reverberates with certain recent suggestions presented in the conversation analytic literature: The points detailed above suggest that the home environment for experience sharing might be in the concurrent framework of emotional reciprocity, while experience sharing  may call for the participants to depart from the sequential framework of turn-taking.not in tension with experience sharing but, instead, serves it.While our first hypothesis questions the relevance of turn-taking for experience sharing, our second hypothesis represents just the opposite view: it suggests that the sequential framework of turn-taking is contingent emotional reciprocity. It can thus be argued that contingent emotional reciprocity, and thus also experience sharing, can be facilitated by the sequential framework of turn-taking.Previously, we highlighted the significance of the automatic resonance processes for experience sharing. However, it has been pointed out that the mere reproduction of other people’s behaviors represents a closed loop system: it reflects what is already out there . So, forIn human ontogeny, the first instantiations of contingent emotional reciprocity appear in the context of alternation between approach and withdrawal tendencies . InfantsIn the subsequent development of the human infant, the experiences of contingent emotional reciprocity get more nuanced. Already from 2 months on, infants and their caretakers start to look and listen to each other more carefully; producing vocal, facial and gestural responses elicited by the expressed feelings and interests of their interaction partners . During From this perspective, let us consider Example wow, gosh, oh my good, ooh, phew have been described as interactionally organized performances, interactional achievements, instead of automatic emotional eruptions , then we would expect that there would be a tension between overlapping vocalizations and effective instrumental communication. While there is some evidence for the tension between turn-taking and experience sharing , the potAccording to the second hypothesis, turn-taking is in the service of experience sharing. In allowing the participants to engage in increasingly complex forms of joint action, and, hence, in ever more exciting shared experiences, there seems to be no tension between turn-taking and experience sharing. From this perspective, there seems to be a developmental continuity between the early infant-caretaker interactions governed by emotional reciprocity and the later, more complex forms of social interaction. If this hypothesis is valid, then there must be evidence that the instances of experience sharing cast in the sequential framework of turn-taking can, in principle, reach at least the same level of intensity as those occurring in the context of overlapping talk. Moreover, one would need to show that occurrences of experience sharing and instrumental goal-pursuit would be relatively evenly distributed between the instances of overlapping talk and talk abiding to the norms of turn-taking.No matter which of the above hypothese is more valid than the other, the relationship between experience sharing and turn-taking is something worth further investigation—something that this paper has sought to highlight.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Acidithiobacillus, Leptospirillum and Acidiphilium exhibited high transcriptional activities. Community-wide comparative analyses clearly showed that the AMD microorganisms adapted to the different environmental conditions via regulating the expression of genes involved in multiple in situ functional activities, including low-pH adaptation, carbon, nitrogen and phosphate assimilation, energy generation, environmental stress resistance, and other functions. Organism-wide comparative analyses of the active taxa revealed environment-dependent gene transcriptional profiles, especially the distinct strategies used by Acidithiobacillus ferrivorans and Leptospirillum ferrodiazotrophum in nutrients assimilation and energy generation for survival under different conditions. Overall, these findings demonstrate that the gene transcriptional profiles of AMD microorganisms are closely related to the site physiochemical characteristics, providing clues into the microbial response and adaptation mechanisms in the oligotrophic, extremely acidic environments.The microbial communities in acid mine drainage have been extensively studied to reveal their roles in acid generation and adaption to this environment. Lacking, however, are integrated community- and organism-wide comparative gene transcriptional analyses that could reveal the response and adaptation mechanisms of these extraordinary microorganisms to different environmental conditions. In this study, comparative metagenomics and metatranscriptomics were performed on microbial assemblages collected from four geochemically distinct acid mine drainage (AMD) sites. Taxonomic analysis uncovered unexpectedly high microbial biodiversity of these extremely acidophilic communities, and the abundant taxa of  The Earth's extreme environments harbor a wide array of microorganisms with the ability to survive and thrive in physical extremes . Analyziin situ metabolic activities and functional partitioning of microbes in these low-diversity communities. To date, the environmental transcriptomes of microbial assemblages in the Tinto River (Spain) ecosystem have been profiled using Leptospirillum ferrooxidans DNA microarrays  polymetallic ore  and another from the acidic drainage pond associated with the tailings impoundment at the Fankou (FK) Pb/Zn mine . The other two samples were collected from the Yunfu pyrite mine , one from the AMD Yunfu stream (YFS) draining across the surface mining area and the other from the AMD collection Yunfu pond (YFP) downstream before treatment. For DNA/RNA extraction, triplicate samples were collected on site by prefiltering through a 1.6-μm GF/A filter to remove impurities and then filtering through a 0.22-μm polyethersulfone filter using a peristaltic pump. Physicochemical characteristics were determined either on site or in the laboratory as previously described .Statistical enrichment of a given gene or COG between two data sets was determined by pairwise comparisons using two-tailed Fisher's exact test, with confidence intervals at 99% significance and Benjamini–Hochberg correction . Hierarchical clustering analysis was performed with correlation distance and average-linkage method using the R package of ‘pheatmap' .-1), and high concentrations of sulfate (6690–7931 mg l-1), total iron (520–2190 mg l-1) and heavy metals   and dissolved organic carbon (DOC) (2.9–6.8 mg l and Mn) , feature and Mn) . SpecifiAcidithiobacillus and Leptospirillum members , for elevated temperature should upregulate the expression of proteins associated with these functions  (kdpABC) , and glutamate, arginine and lysine decarboxylation   proteins, the transcriptional repressor LexA (lexA) and nucleic acid-binding proteins of Hu (hupB) and Dps (dps), were also expressed in all four communities  . In addi(kdpABC)  indicate protons . The cytA, cadA) . Moreovemunities . Our anator COGs . These rtor COGs .-1; Acidithiobacillus spp. and/or Leptospirillum spp. were the main carbon fixers in the analyzed AMD communities, as the genes encoding the key enzymes for Calvin–Benson–Bassham cycle and reductive tricarboxylic acid cycle were highly expressed  in all analyzed AMD samples. Therefore, the knowledge of nitrogen fixation and assimilation mechanisms used by the AMD microorganisms is critical to the understanding of how they respond and adapt to the nitrogen-limited conditions  in all the four communities (L. ferrooxidans (group I), L. ferrodiazotrophum (group III), At. ferrivorans and Acidithiobacillus sp. GGI-221. This result indicated the key role of these taxa in nitrogen fixation of the communities, despite the relatively low abundance of the nitrogen-fixation transcripts (5–27 transcripts). The genes for ammonium transporter (amt) showed high transcriptional activities in all communities (glnA) and glutamate synthase (gltBD), which would permit the incorporation of ammonium into glutamine and then to glutamate for utilization  exhibited very low transcriptional activities  were highly abundant in our cDNA data sets  that the AMD communities, especially that of YFP, which exhibited the highest expression levels of these genes  to uptake protons to generate ATP (2 to generate H2O with the consumption of electrons from ferrous iron (Fe2+) and/or sulfur oxidation , superoxide dismutase (sodA) and hydroperoxide reductase (dnaX), with the majority of which was associated with the active taxa , although those in DBS and YFP exhibited generally more similar activities  showed high activities in the uptake of phosphate. Moreover, At. ferrivorans in DBS and YFP may execute assimilatory sulfur reduction for the utility of sulfur as indicated by the upregulation of sulfite reductase genes of cysI, cysJ and cysH. Collectively, these lines of evidence indicate that At. ferrivorans in YFS contributed more for carbon, nitrogen and phosphate assimilation, whereas those in DBS and YFP were likely active in sulfur assimilation.The majority of the significantly different transcripts  compared with those in DBS and FK. For the carbon-fixation activity, all genes of the reductive tricarboxylic acid cycle in L. ferrodiazotrophum  were also detected, with the highest expression levels in YFS. These results suggest that this organism in YFS contributed much in the fixation of carbon and nitrogen via Fe2+ and sulfur oxidation, as At. ferrivorans did in the same community (see above). We further identified the genes for proteasome, which collectively accounted for a transcript abundance of 0.44%, 1.45% and 0.93% in DBS, FK and YFS, respectively  proteins and phage integrase proteins (Similar to those of fixation ; howeverotrophum , with a otrophum , and thootrophum . The genectively . Within ectively  and Leptproteins , implyinAt. ferrivorans and L. ferrodiazotrophum in YFS contributed more transcripts for carbon and nitrogen assimilation than their counterparts in other communities. The ecological significance of less active taxa, including their irreplaceable role for the whole-community function as well as their contribution in community assembly and dynamics, has been documented in marine environment (Our comparative metagenomic and metatranscriptomic analyses have provided a detailed gene transcriptional blueprint for the naturally occurring, low diversity microbial communities in the extreme AMD environments, demonstrating how these extraordinary microorganisms respond and adapt to the different physicochemical conditions at both community- and organism-level. The transcriptional analyses of dominant transcripts and indicator COGs revealed a high diversity of transcripts harbored by these acidophilic assemblages. These transcripts were associated with a wide range of functions, the expression levels of which were closely related to the physicochemical characteristics of the AMD systems. In particular, the detection of nitrogen-fixation transcripts provided clues for nitrogen-fixing activities in AMD communities. Detailed analysis of the transcriptional behaviors of the most active organisms revealed differential gene expression patterns, likely reflecting their distinct roles and life state in different communities. For example, both