In cognitive psychology, classical approaches categorize automatic and controlled processes from a dichotomous point of view. Automatic processes are believed to be rigid, whereas controlled processes are thought to be flexible. New theories have softened this dichotomous view. The aim of the present study is to examine the possibility of implementing flexibility in automatic processing through reliance on contextual features. One hundred and twenty subjects , 60 male and 60 female, participated in this study. An automatic sequence task  was used to test flexibility in automatic processing. Results showed that the use of contextual cues can increase flexibility in automatic processes. The results are discussed in light of new theories on softened automaticity. The first distinction between automatic and controlled processes was introduced by According to classical theories of cognitive control and automaticity, automaticity has been considered as an all-or-none phenomenon, that is, a process is either automatic or controlled. Controlled processes were considered exclusive to the domain of conscious cognition, and automatic processes were thought to be in the domain of unconscious cognition . This clThis behavioural switching can occur either retroactively based on error feedback or proactively by detecting a contextual cue , so, it Unlike classical theories, refined theories of automaticity and unconscious processing allow for more flexibility and adaptability of unconscious automatic processing . These tIn line with aforementioned new theoretical perspectives, a key issue for researchers is to understand whether and how automatic processes can be flexible and adaptive in spite of their apparent rigidity. One potential answer to this question is that automaticity gains flexibility through sensitivity to contextual cues . ContextIn light of this knowledge gap, the main focus of the current paper is to analyze how the learned task could become more flexible through the inclusion of context-specific features. In this study, learning of a sequence task was used to test automatic processing. According to previous studies  automatiThe specific aim was to demonstrate that participants can increase the processing speed (automatization) of two sequence tasks, and that this increment can be tied to contextual features associated with the two tasks. The first goal of this study was to induce an automatization process of two sequence tasks. The second aim was to examine whether the contextual features influenced flexibility on the learned sequences.The role of contextual features was evaluated through the manipulation of the distinctiveness of contextual information. In the condition with contextual cue, we helped the subject to recognize the target by providing two different contexts for each different target. In the condition without contextual cue, the context was always the same.Summarizing, we hypothesized that: 1) when the subjects identified the same target stimulus during many trials (first sequence), speed of execution and accuracy in the identification of target would increase ; 2) after the first sequence automatization, the target changed in two different ways: with and without contextual distinctiveness (cue), therefore we awaited that subjects in the condition without contextual-cue would show a loss of processing speed; whereas in the condition with contextual-cue, the subjects might not show this loss; 3) successively a second sequence with the second target for many trials was presented and when the two targets were intermixed (and the controlled processes were necessary to identify the two different targets), we awaited that the loss of processing speed and accuracy should be higher in the condition without contextual-cue.SD = 4.2), 60 male and 60 female, participated in this study. They were individually asked to indicate their level and type of education: 62% of the subjects had been or were about to achieve a secondary diploma in the scientific or humanistic field, 38% had a bachelor's degree or worked. All participants had normal or corrected to normal vision. Participants were recruited through an article in the local newspaper, a university e-newsletter, and networks of acquaintance. Each subject voluntarily agreed to participate in this research study. After providing informed consent, they were tested individually.One hundred and twenty subjects between 18 and 30 years ; and with an intermixed presentation of the first and second target . The loss of processing speed, between the 3rd and 4th trial, and after, between the 6th and 7th trial, was considered an index of the rigidity/flexibility continuous process.Following this stimulus sequence, we wanted to induce an automatization process of two target clock-faces and we also evaluated flexibility in two ways: with the shift of the target clock-face after the first target was automatized ; as many works suggest, processing speed measures automaticity and fluency of cognitive performance across a wide variety of tasks .The number of false alarms—FA (erroneous “detection”) that measures the accuracy of performance.Data were analyzed using SPSS 14.0 for Windows. The descriptive statistics of the dependent variables were tabulated and examined. Alpha-level was set at .05 for all statistical tests. In the case of significant effects, the effect size of the test was reported. The effect sizes were computed and categorized according to first learned sequence, with the first three trials indicating the 4 target, to detect automaticity of the first target; 2) second learned sequence, with the second three trials indicating the five target, to detect the automaticity of the second target; 3) Target shift , to detect the rigidity/flexibility due to the shift; 4) Intermixed task  ), to detect the rigidity/flexibility due to the the intermixed stimuli.Results are presented, as mentioned in the procedure section, with reference to 4 units: 1) F = 199.45, p < .0001, d = 0.90 and F = 298.21, p < .0001, d = 0.90. This result indicated that when subjects identified the same target stimulus in many trials the speed of execution and accuracy (decrease in the number of errors) increased, respectively, from 27.50 and 27.90 to 35.60 and 34.80 and from 16.95 and 14.69 to 8.79 and 6.886  = 218.56, p < .0001, d = 0.90 and F = 78.45, p < .0001, d = 0.81. This result indicated that the subjects automated the new target both in condition with and without contextual cue, from 35.50 and 27.43 to 37. 91 and 33.90 and from 13.58 and 10.74 to 6.43 and 6.25. Similarly, in this sequence task, the contextual cue was added as a counterbalancing condition, and, as expected, it had no statistical effect.With reference to both CR and FA, the “sequences” factor showed significant effects, respectively t-test for dependent measures was carried out. We compared the performance in trials in which the target clock-face was shifted , in both conditions. Results showed no significant effect in the condition with the contextual cue, t(119) = 0,34; p = .61. A significant effect in the condition without contextual cue was found, t(119) = 4.41, p < .05. As expected, without contextual cue, the subjects showed a loss of processing speed in the trial in which the target changed. Whereas the subjects did not show a loss of processing speed in the trials with contextual cue. These results evidenced the role of contextual features in flexibility.CR of the third and fourth trials are presented in t-test for dependent measures was carried out. We compared the performance between the sixth and seventh trials in both conditions. Results showed no significant effect in the condition with contextual cue for the two clock-face targets, t(119) = 0.16; p = .81 and t(119) = 0,02, p < .62. As expected, a significant effect in the condition without contextual cue for both target 4 and 5 was found, respectively t(119) = 8.23, p < .03, and t(119) = 6.26, p < .05. Similarly, in the intermixed task, the participants showed a loss of processing speed without contextual cue.CR of the seventh trial is presented in The specific aim of the present study was to demonstrate that participants can increase processing speed (automatization) of two sequence tasks, and that such increment can be tied to contextual features associated with the two tasks. The first goal was to induce an automatization process of two sequence tasks. Secondly, we examined whether contextual features influenced flexibility on the learned sequences.As expected, the results showed that when subjects identified the same target stimulus on the first and second learned sequence, the speed of execution and the accuracy (decrease in the number of errors) increased. Therefore, performance improved through exercise, and, the two sequence tasks were learned progressively. These results are in line with the classical theories of skill acquisition  for whicWith reference to the second goal, results indicated that contextual features influenced flexibility on the learned sequences. More precisely, the target shift (unexpected change of the stimulus to detect), which requires reactivation of the controlled processes, produced a loss of processing speed in trials without contextual-cue, whereas, in the condition with contextual-cue the subjects did not show loss of processing speed. Furthermore, we also found loss of processing speed when the two targets were randomly intermixed in the without contextual-cue condition compared to the condition with contextual-cue. Thus, it seems plausible to assume that contextual features play an important role in automatization processes. The difference between the performance in the target shift and in the intermixed task reveals that the benefits of automation are higher and more significant when the subject was presented the contextual-cue. These results are in line with literature on context-specific proportion congruent effects showing evidence for flexible transfer of context-specific control across different items .It is interesting to note that when participants identified the same target on the first and second learned sequence, the contextual cue had no effects. These two sequences implied activation of the automatic processes. In addition, the process became more automatic after the first learned sequence, and the controlled processes were again needed at the start of the second learned sequence. Instead, when the subjects simultaneously detected two targets in the intermixed task, the contextual cue showed a significant effect. This task required the activation of both controlled and automatic processes. Thus, all the results indicate that participants can switch between both processes and that context cues facilitate this switching. Therefore, it is reasonable to assume that contextual features facilitate the activation of controlled and automatic processes and that a learned task can become more flexible through the inclusion of context-specific features.In light of the above, the present study aim to fill the knowledge gaps about the conditions under which the contextual cue is involved in the automatic processing. In particular, with reference to previous studies , 2014, tMoreover, Other previous studies investigated the conditions that promote feature search . More spIn short, we assume that the effects of context are a consequence of the experimental design used. Future research is required to support for this view. Anyway, the current study introduces significant novelty about the methodological strategies under which is possible to analyze the effect of contextual features on automatic processing of two learned sequences.From a conceptual point of view, the present study suggests that the classical distinction between automatic and controlled processing as separable processes can be softened, as the automatic processes can gradually become flexible and context-dependent, as shown in this work. Also, our findings have a theoretical implication; they highlight the necessity to reconsider the classical theories and support the refined theories of automaticity, which assume more flexibility and adaptability of automatic processing . From thIn conclusion, the present study highlights two key points: the first concerns the possibility that context-specific features can affect the learned task and can implement flexibility in automatic processing; and the second concerns the revision of theories on automaticity in the direction of the complex model in which automatic and controlled processes are conceptualized as two continuous processes which interact with each other. It is instructive to look at the role of contextual features in a cognitive task from a complex prospective, by recognizing that human performance often results from an interplay between automatic and controlled processing and these processes may be mediated by systems that evolve to satisfy the need for operation in a complex environment, where attention must be guided to process selectively critical stimuli.The authors declare that they have no conflict of interest and no funding. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.


Penta-graphene (PG) is a carbon allotrope that has recently attracted the attention of the materials science community due to its interesting properties for renewable energy applications. Although unstable in its pure form, it has been shown that functionalization may stabilize its structure. A question that arises is whether its outstanding electronic properties could also be further improved using such a procedure. As PG bilayers present both sp The properties of graphene are truly unique3, and a wide range of applications have been predicted for this carbon allotrope4. Although the overall success of graphene,there are still some limitations to be overcome regarding its optoelectronic applications, the main being its null bandgap5. For that reason, other two-dimensional materials have been extensively tested. Among them, transition metal dichalcogenides (TMDs)8 and novel graphene-based allotropes11 stand out. However, graphene allotropes still hold an important advantage over TMDs, for instance, of being formed only by carbon atoms, which makes it easier to synthesize on a large scale. Therefore, it would be ideal to conceive a material that, while presenting semiconducting properties would still be based on graphene.The interest in two-dimensional extended nanostructures was further highlighted after the graphene arising17. For instance, studies concerning graphene bilayer concluded that its structural properties are altered from a suitable layer stacking engineering20. In one of these studies, it was obtained that the rotation of one graphene layer over another one leads to the displacement of the Dirac cones, but no gap opening was observed18. The conclusion is that layer stacking still need to be associated with other procedure if a graphene-based system with semiconducting properties is to arise. So far, the main option relied on substitutional doping24 on graphene structure. Density functional theory (DFT) calculations were performed to study the doping of boron (B) and nitrogen (N) in graphene bilayers25. The results revealed that for doping with B (N), a gap opening from 0.11 to 0.32 eV (0.09 and 0.30 eV) was obtained, being these values depend on the type of bilayers packing25.Having such a goal in mind, several theoretical and experimental studies have been conducted to achieve alternative solutions to monolayer graphene26, nanoribbons27, nanoscrolls28, and novel graphene-based allotropes, such as popgraphene11, phagraphene10, and penta-graphene9 (PG). In its pure form, the PG structure is meta-stable but presents an almost direct bandgap 9. Such a structure allows more degrees of freedom for doping when contrasted to graphene. As a result, different ways of modulating its electronic properties can be obtained29. Particularly, it can be reasoned that the flexibility of such material makes it a promising candidate to fulfill the role of the carbon allotrope with semiconducting-like properties. This fact is especially true if one considers the two promising factors on PG: considering bilayers and substitutional doping.Another approach is to study other possible arrangements: different, and yet based on graphene. Among them are carbon nanotubes32. Such a trend is attributed to the up-shift of the conduction band minimum during the oxidation process30. Since oxidized PG exhibits a large bandgap, it can be considered a good alternative for the conception of new dielectric layers in electronic devices31. When it comes to doped carbon-based nanostructures, boron and nitrogen are the most often used dopants once their similar electronic structure and size to carbon allow their incorporation into the carbon-based substrate with minimal strain and changes in the lattice arrangement38. Moreover, the boron- and nitrogen-doped PG can effectively decompose H2 molecules into two H atoms, which is an interesting feature for energy conversion and storage applications39. In this sense, oxygen-, nitrogen-, and boron-doped PG systems must be further studied to propose new routes in developing PG-based devices.It is well known that the PG bandgap increases with an increase in oxygen doping concentrationIn the present work, we explored the structural and electronic properties of doped PG bilayers by carrying out state of art electronic structure calculations on the DFT level of theory. This study was motivated by the fact that PG has more degrees of freedom to modulate its electronic properties than graphene. We used as substitutional dopants boron, nitrogen, and oxygen atoms. It was observed that the introduction of oxygen atoms in the sp41. In a reactive molecular dynamics study, the results have revealed that oxygen-doped PG layers present remarkable enhancement in failure stress and strain when contrasted with pristine PG layers40. Moreover, it was recently demonstrated, by using DFT calculations, that boron- and nitrogen-doped PG layers are structurally stable when concentrated with pristine PG layers39.We begin our discussions by presenting the structural properties Fig.  and the B–C slightly deviate from that of the bond length C–C in the pristine monolayer, which is 1.57 Å. These bond lengths (B–C) assume minimum and maximum values of 1.51–1.61 Å for all the cases of doping with B. As for the oxygen doping picture, represented by Fig. N–C also slightly deviate from the C–C ones in the pristine case. These bond lengths (N–C) assume minimum and maximum values of 1.38–1.52 Å for all doping channels.Figure mentclass2pt{minimmentclass2pt{minimmentclass2pt{minimmentclass2pt{minimThe charge density wrapped around the dopant is depicted in Fig. X stands for B, N, or O. The first row of Table 9. In the case of doping with boron  is observed. Still, for these two cases, we observed that the Fermi level is closer to the valence band, which characterizes a n-type semiconductor. The N-spn-type semiconductor, once the Fermi level is touching the top of the valence band. In the case of oxygen doping  + vDW46, which is built from the expansion of the second-order density gradient. Pseudopotentials parameterized within the Troullier-Martins formalism are also considered47. This approximation is of fundamental importance for the description of the magnetic and electronic properties of materials composed of atoms with many electrons. All calculations were performed considering spin polarization. To calculate the bands and state densities, an MPK mesh of 15 48. A mesh cut of 200 Ry is chosen as a parameter for our calculations49. The forces converged until reaching a minimum value of 0.001 eV/Å. In order to ensure a good compromise between the accuracy of our results and the computational feasibility, the tolerance in the density of the matrix and the total energy was set at 0.0001 and 0.00001 eV, respectively. Importantly, this set of parameters were used recently to study other carbon-based lattices52.To investigate the electronic structure of doped PG bilayers, we used DFT calculations as implemented in the SIESTA softwarep, whereas the substituted carbon has a pair of electrons in this same orbital. Therefore, the C–B and C–N bonds result in a magnetic polarization due to electronic covalence. This effect is characterized by the flat energy levels that appear in the middle of the bandgap for the cases of boron and nitrogen doping in the spn-type semiconductor. On the other hand, for the oxygen doping in the spp-type semiconductor. Since the electronic structure of PG bilayers present extra doping channels and can be easily tuned by doping its structure with just a single atom, they can represent an interesting alternative for replacing graphene in some optoelectronic applications.In summary, we carried out DFT calculations to investigate the influence of boron, nitrogen, and oxygen doping on the electronic properties of PG bilayers. Our findings showed that the difference between dopant on the sp


An experimental and theoretical investigation on microwave plasma-based synthesis of free-standing N-graphene, i.e., nitrogen-doped graphene, was further extended using ethanol and nitrogen gas as precursors. The in situ assembly of N-graphene is a single-step method, based on the introduction of N-containing precursor together with carbon precursor in the reactive microwave plasma environment at atmospheric pressure conditions. A previously developed theoretical model was updated to account for the new reactor geometry and the nitrogen precursor employed. The theoretical predictions of the model are in good agreement with all experimental data and assist in deeper understanding of the complicated physical and chemical process in microwave plasma. Optical Emission Spectroscopy was used to detect the emission of plasma-generated ‘‘building units’’ and to determine the gas temperature. The outlet gas was analyzed by Fourier-Transform Infrared Spectroscopy to detect the generated gaseous by-products. The synthesized N-graphene was characterized by Scanning Electron Microscopy, Raman, and X-ray photoelectron spectroscopies. These features arise from the unique nature of graphene’s charge carriers, which behave like relativistic particles. Thus, it is not surprising that graphene is seen as a promising material in nanoelectronics, “classical” microelectronics, as well as in spintronics, artificial neural networks, etc. [π state, and the fifth fills π* state of the conduction band of graphene, thus leading to n-type  doping [The existing variety of carbon structures is due to the ability of the carbon atom to form different hybridizations, such as tetrahedral spcarbyne) . Graphenks, etc. ,5. It isks, etc. ,7,8,9,10) doping ,14,15,16) doping ,18,19.Among various synthesis methods of graphene and graphene-related structures, plasma-based techniques have emerged as an eco-friendly and energy-saving alternative. For instance, one of the most common graphene synthesis methods, i.e., chemical vapor deposition (CVD), was significantly improved with the inclusion of plasma . In the 2 or ammonia plasma processing to previously synthesized graphene [N-graphene was successfully synthesized by nitrogen plasma treatment of graphene with regulated doping level, ranging from 0.11 to 1.35 at % N . Radiofrgraphene ,27,28,29graphene . Doping graphene ,31. Howegraphene ,39,40,412-based supercapacitive electrodes [2 gas as a graphene doping agent is experimentally and theoretically investigated. The theoretical studies were focused on revealing the main mechanisms of precursor’s decomposition and creation of the new species involved in the formation of N-graphene structures. For this purpose, the previously developed chemical kinetics model was updated with nitrogen-containing species and the corresponding rate coefficients.In this study, microwave plasma at atmospheric pressure was used for direct synthesis of free-standing N-graphene sheets. The work is a continuation of the research carried out within the framework of plasma-based synthesis of advanced 2D nanostructures, which includes graphene ,34,35,37ectrodes . In the A waveguide-surfatron-based setup was used to create a surface wave (SW)-induced microwave plasma at atmospheric pressure conditions . SW-sust2 are the carbon and nitrogen precursors, respectively. The flow of the gas mixture injected into the plasma reactor and the applied microwave power (p = 2 kW) were kept constant. The ethanol was kept at a narrow range of flow rates which ensure graphene assembly. A set of experiments were performed varying the N2 gas flow (QN2) injected into the plasma. The created nanostructures were captured by a tornado-like collecting system and accumulated in a glass container.The discharge takes place inside a quartz tube inserted perpendicularly to the waveguide wider wall and directed downstream . OptimizOptical Emission spectroscopy (OES) was applied to detect the emission of the plasma-generated “building units” and to determine the gas temperature. Optical fiber was placed perpendicularly to the discharge tube and directed to the entrance of a Jobin-YvonSpex 1250 spectrometer (1200/2400 g/mm grating) equipped with a charge-coupled device (CCD) camera. The cryogenic, back illuminated ultraviolet (UV)-sensitive CCD camera has a 2048 × 512 matrix, featuring a 13.5 µm pixel-size, which provides high spectral resolution. The plasma emission spectrum in the 230–800 nm range was detected.−1 absorption spectra of species in the plasma outlet gas. The 2D map of the temperature at the reactor walls was monitored with thermal imager (FLIR systems).A FT-IR Thermo Nicolet 5700 spectrometer was used to investigate the 1000–4000 cmScanning Electron Microscopy (SEM) characterization of the samples was performed using a JEOL, JSM-7001F field emission gun scanning electron microscope operating in secondary electron imaging mode (SEI) using 15 kV of accelerating voltage. The samples were deposited on a double-sided carbon tape mounted on an aluminum stub.−1 and a 633 nm He-Ne laser excitation with laser spot size of 2 μm. The synthesized nanostructures were freely suspended on a glass substrate and the Raman spectra from different regions on the substrate were obtained. Measurements were performed with a laser power p = 0.054 mW to avoid overheating.Raman spectroscopy of the samples was carried out using a LabRAM HR Visible (Horiba Jobin-Yvon) Raman spectrometer with a spectral resolution of 1 cm2 carbon atoms in graphene [N-graphene samples were also characterized by X-ray Photoelectron Spectroscopy (XPS) using a XSAM800 spectrometer from KRATOS Analytical. The incident radiation, Mg Kα X-rays with 1253.6 eV, was produced with a power of 120 W. Spectra were acquired in Fixed Analyzer Transmission (FAT) mode, with high magnification and a pass energy of 20 eV. Charge shift was corrected using as reference the binding energy 284.4 eV, assigned to spgraphene . Samplesgraphene .2) and around 20 new reactions from the kinetic mechanism of Konnov [•, NH3, NH2, NO2, HNO, NO, N2H, N2O, H2CN, HNO2, HCNO, NCO, HNCO, C2N2, and N2 are considered and the reaction mechanism with the corresponding rate coefficients is included. To find the most reliable values for the rate constants, extrapolation to the upper border of the experimentally determined temperature range (~3000 K) using a non-linear extrapolation method that solves the Fredholm integral equation was used [A previously developed theoretical model describing the chemical kinetics and the thermodynamics in the microwave plasma medium ,40,43,44f Konnov  and GRI f Konnov  was addewas used . The expwas used ,53,54,55was used ,37. The was used ,40kest=2. The estimated coefficient estk was tested by adopting the factor k0 as a free parameter. The best fit for k0 with the experimental results was found to be very close to the estimated diffusion rate coefficient of carbon species (k0 = 24), which supports the initial assumption of the diffusion nature of the carbon transport.Here the factor The minimization of the Gibbs energy of the system was used in the equilibrium approach, while a set of differential equations is solved in the non-equilibrium approach. The chemical kinetic scheme was used to generate a set of differential equations, i.e., the system of non-linear mass balance equations and the total energy-conservation equation.i is the species index; iY is the mass fraction of species i; i (mol cm−3 s−1), i (mol cm−3 s−1), −1); ns is the total number of species; −3) and t denotes the time (s).The mass balance is then represented by the set of equations:ns chemical species: The equation is solved in time until the steady state is reached. Additionally, a normalization condition accounting that the total mass fraction is given by i-th species can be written as a summation of the rate-of-progress variables for reactions involving the i-th species, as shown in Where r-th reaction are provided by the difference between the forward rates ‘1’ and the reverse rates ‘2’ as r-th reactions and i-th species. The effective rate constants A is the pre-exponential factor, n is the temperature exponent, and The rate-of-progress variables operties .rk are the rate coefficients of the elementary reactions and ic are the species concentrations. Eigenvalue analysis of the chemical reaction system is defined as in [The behavior of the set of differential equations was investigated using the relative sensitivity and eigenvalue analyses. The relative sensitivity is defined as : Si,rreled as in , i.e., t process .−1) is the initial gas velocity, T0 (K)-the initial gas temperature, p0 (Pa)-the gas pressure, pC = (5/2)Bk-the heat capacity at constant pressure, S-the plasma cross-section, P-the absorbed microwave power; δ is a coefficient expressing the fraction of absorbed power from the wave that is transferred to thermal energy of the gas. Here, the electron energy balance equation is implicitly included via the coefficient δ. Around 10% energy losses due to radiation and losses in the dielectric are assumed.The microwave power is absorbed primarily by plasma electrons, which transfer the power to heavy particles via elastic and inelastic collisions and high gas temperatures (up to 3000 K) are achieved. The gas temperature slightly decreases in the “hot” discharge zone when moving away from the launcher , C2 , CH (A2Δ-X2Π) at 431 nm, CH (C-X) at 310 nm, OH (A2Σ+→ X2Πi) and C atoms (247.9 nm). The dominant vibrational bands are C2 (Swan bands) and CN• (B-X) violet system. The typical C2 emission is generated by the radiative decay of the C2*(A3Πg) state resulting in the cyan–green color of the plasma (photo in ext = 2.4 eV), ground state C2 molecules can easily be excited to this level either by electron impact C2(X) + e → C2*(A3Πg) + e or by three body recombination processes involving C and Ar atoms C + C + Ar → C2*(A3Πg) + Ar. Additionally, atomic carbon is formed in dissociation reactions of C2 molecules with hydrogen radicals.The plasma optical emission spectrum in the visible range (230–800 nm) was investigated . New molphoto in . Due to • or OH molecules [• in the range 380–388.3 nm was used to estimate the rotational temperature using Lifbase software [The gas temperature in atmospheric pressure microwave plasma is typically estimated assuming local thermodynamic equilibrium and using rotational spectra of CNolecules ,37. Thussoftware . By matc2) directly into the “hot” plasma zone, where their decomposition takes place. As a result of the particles collisions and multiple chemical reactions the precursors decompose down to carbon atoms and C2 radicals, which are the main components of the targeted materials, i.e., graphene-based structures. Additionally, nitrogen-containing species such as CN•, HCN NH2, NH3 are formed. The newly created species move towards colder zones , passing through an area with nearly constant temperature (~2500 K), the so-called “vaporization boundary” . Inversely, formation of more carbon atoms leads to increased synthesis of sp3 carbon systems [It should be noted that a correlation between changes in C earlier . Presenc systems .The gas temperature is an essential parameter regarding plasma kinetics and is an input value in the numerical calculations. In our earlier works ,37 a qua2 plasma was investigated using FT-IR spectroscopy. The spectra detected with the plasma on and off, at typical operational parameters for N-graphene synthesis , are shown in 2H2, and HCN. C≡O has a major absorption band at 2100 cm−1, due to asymmetrical vibration modes. The bands in the C2H2 spectrum can be assigned to –C≡C– stretching at 2260–2100 cm−1; –C≡C–H: C–H stretching at 3330–3270 cm−1; –C≡C–H: C–H bending at 700–610 cm−1. HCN normal vibration modes such as ν2 (a doubly degenerate bending) at 712.1 cm−1, ν3 (C-H stretching band) at 3330 cm−1 were observed. The features at 1412 cm−1 and 2117 cm−1 are the 2ν2 and 3ν2 overtones of the ν2 fundamental mode. The absorption spectrum of the Ar/Ethanol/N2 outlet gas under the same conditions but without plasma exhibits the peaks characteristic for ethanol molecules, associated with both the O-H at 3200–3500 cm−1 and the C–O stretching vibrations at 1050–1260 cm−1 [2 and CO [p = 2 kW, QAr = 1330 sccm, QEt = 35 sccm) shows increase in the relative intensity of acetylene bands.The outlet gas stream from Ar/Ethanol/N260 cm−1 ,58. The 2 and CO . Additio2H5OH/N2 and Ar/C2H5OH a substantial difference is not observed, which implies that the presence of nitrogen does not interfere with the basic principles of ethanol decomposition established earlier [2 and H2 to gas-phase carbon and atomic hydrogen (for temperatures above 3500 K). No fundamental difference was found in the list of species and concentrations of CxHyOz by comparison with [The calculated concentrations of the main decomposition products obtained under thermal equilibrium assumption are shown in  earlier ,40. Four• appears at temperature > 4000 K. Naturally at temperatures above 4000 K, hydrogen is detached from C–H as a more fragile bond compared to C=N shifting towards CN• formation. The concentration of atomic carbon and nitrogen is significant above 3200 and 3700 K, respectively [The representatives of carbon–nitrogen species in the plasma are HCN and CN: HCN forms in the temperature region 2000 to 4000 K, while CNectively .2, C, C2H2, C2H, C2H4, CH4, C3H6 etc., while N2 does not dissociate directly. Above 1500 K, the chemical reactions rates increase significantly, so the time to reach equilibrium is reduced to a few microseconds and the assumption of local thermal equilibrium is valid. At this conditions radicals and species containing nitrogen, i.e., NH2, NH3, CN•, HCN, N, etc., start to form. These reactions occur in the chemically active zone, which is enhanced in the new reactor geometry, therefore benefiting the formation of N-graphene. For this reason, in the following experiments the N-graphene synthesis was performed using the new reactor featuring the expanding radius geometry.The results of the non-equilibrium modeling, i.e., the axial variations of the concentrations of the main decomposition products considering ethanol/nitrogen precursors, are presented in •, N-graphene, and C(solid)  . AdditioC(solid) .2 also affect the relative amount of solid carbon. The absolute difference between H2 and C(solid) sensitivity coefficients is due to the fact that part of the hydrogen is formed by the first mechanism, i.e., breaking the C-C bond, leading to formation of syngas (H2 and CO) and is, therefore, independent of the carbon diffusion rate. On the other hand, the solid carbon is only created by the second decomposition mechanism, i.e., OH group is detached from the ethanol molecule forming, after multiple reactions, C, C2, and H. The solid carbon formation is not related to the CO generation. CO is only created through the first mechanism and does not depend on the carbon diffusion rate.The simulation results, the sensitivity analysis and the integral reaction analyses of the kinetic mechanism in the “hot” plasma region indicate that the ethanol decomposition occurs through two parallel, approximately equivalent mechanisms , as prev2, and partially, through interactions with radicals, such as CH2, CH etc. In this case, the formation of CN• is dominant:The nitrogen molecule does not dissociate directly; the formation of nitrogen-carbon species occurs through reaction with C and CAt the same time, the CN radical is not directly involved in the formation of nitrogen-doped graphene structures. In the chemically active region, a change of mechanisms occurs:The free nitrogen atom, generated in the reaction  mainly bonds with hydrogen and is involved in the formation of another by-product, i.e., ammonia:Since N-graphene formation is closely related with the presence of HCN, optimal temperature for this process is around 3000–4000 K, when HCN concentration reaches maximum values see .2H2 and HCN leading to formation of acrylonitrile CH2=CH–C≡N [2H2 in the FT-IR spectrum of Ar/C2H5OH/N2 in respect to the one in Ar/C2H5OH plasma output gas  into nucleation centers that can either grow as 2D or 3D structures, depending on the thermodynamic conditions and the concentrations of carbon species  + CN• = N-graphene and C(solid) + N = N-graphene and that the rate of formation of N-graphene is limited by the rate of formation of C(solid).The description of the actual growth process of the free-standing graphene/N-graphene cannot be achieved in the frames of the current Equilibrium and Rate balance equation approaches, but requires complex ab initio quantum methods. These notoriously complex models will be addressed in the next stage of development of the theory for the formation of the free-standing graphene-like structures. At this stage however, the description of the substrate-free graphene/N-graphene formation is limited to equilibrium and non-equilibrium approaches. For the purpose, several simplified equations are included in the non-equilibrium model, to provide quantitative estimation of the process. The formation of graphene was estimated by the rate of formation of C(solid), already existing in the heterogeneous chemical kinetics model. We assume that formation of N-graphene is governed by the reactions: C(solid) + HCN = N-graphene + 1/2HAr = 1320 sccm; QEt = 30 sccm; QN2 = 30 sccm; p = 2 kW. Sheets are the only allotrope present in the sample; in this sense, the presented SEM image is representative for all the samples. It reveals the characteristic free-standing graphene morphology, consisting of curved ultrafine sheets [A SEM image of the N-graphene is shown in e sheets ,37,38,40−1 attributed to D, G, and 2D bonds, respectively. The G peak is typical for all sp2 carbon systems, representing the in-plane vibrations. The position of D and D´ peaks depends on the excitation photon energy. Their intensity depends on the type of the defects and their concentration in the layer as well as on the size of graphene flakes. The 2D peak corresponds to the overtone of the D band and its intensity and shape is very sensitive to number and the stacking order of the graphene sheets [−1 for both pure graphene and N-graphene suggesting that these structures are predominantly composed of several-layers [The Raman spectra of the synthesized N-graphene and pure (undoped) graphene are compared in e sheets . As it cl-layers ,37,38. Tl-layers . Raman sAnalogous results are reported in , were suEt/QN2 = 30/30; 30/50; 35/10, respectively , with part of nitrogen apparently being lost as gas-phase NThe presence of nitrogen in the plasma environment does not change the main mechanism of ethanol decomposition, as previously investigated.• radical does not directly participate in the formation of nitrogen-doped graphene structures.The nitrogen molecules do not dissociate directly. The formation of carbon–nitrogen species mainly occurs in reactions with gaseous atomic and molecular carbon. The CNThe process of HCN attachment to the graphene-like structures which takes place in the chemically active region is the main mechanism of N-graphene formation.The new reactor geometry, with increased cross-section, was found to influence the nitrogen doping, since it provides an enhanced chemically active zone where the nitrogen-containing species form and attach to the graphene structure.The theoretical predictions of the updated model are in a good agreement with all experimental data and can assist in deeper understanding of the complicated physical and chemical process in microwave plasma.Free-standing N-graphene sheets with high structural quality as demonstrated by Raman and SEM analysis were synthesized.2 as precursor, relatively low doping levels, with nitrogen in pyridinic/pyrrolic configuration, as attested by XPS, and low production yields (0.1 mg/min) were achieved.Using NIn this study, experimental and theoretical investigations of a microwave plasma-based direct synthesis of free-standing N-graphene sheets using ethanol and nitrogen as precursors are presented. The work is a continuation of a series of investigations related to plasma-enabled synthesis of advanced 2D nanostructures. The updated theoretical model, considering the nitrogen precursor, is based on plasma thermodynamics and chemical kinetics mechanism of ethanol decomposition. The main results can be summarized as follows:


Graphene has received extensive scholarly attention for its extraordinary optical, electrical, and physicochemical properties, as well as its compatibility with silicon-based semiconductor processes. As a unique two-dimensional atomic crystal material, graphene has excellent mechanical properties, ultra-high carrier mobility, ultra-wide optical response spectrum, and strong polarization dependence effect, which make it have great potential in new optical and polarization devices. A series of new optical devices that are based on graphene have been developed, showing excellent performance and broad application prospects. In this paper, the recent research progress of polarizers, sensors, modulators, and detectors that are based on the polarization characteristics of graphene is reviewed. In particular, the polarization dependence effect and broadband absorption enhancement of graphene under total reflection structure are emphasized, which enhance the interaction between graphene and light and then provide a new direction for research of graphene polarization devices. Increasre (HCC) ,4, whichre (HCC) . The excre (HCC) ,7,8 makere (HCC) ,10. It aThe optical properties of graphene ,12,13,14plasmons . Moreovent light . AlthougLight waves are transverse waves, and polarization is one of their important properties. It can also have different polarization states when transmitting in the same direction. In optics and optoelectronics, it is often necessary to detect the polarization characteristics of light, change the polarization state, and use the polarization characteristics to indirectly measure the changes of some physical quantities . Opticalnication ,20,21, bnication ,23,24, inication , and sooIn conventional polarizers that are based on the semiconductor quantum well structure, since metals are used, they are generally designed while using Drude models. Meanwhile, the imaginary part of the conductivity of the metal is greater than 0, which can only be designed as a TM polarizer . There aOptical fiber polarizer is a part of the most important optical passive devices in the optical fiber system, which is characterized by polarization or phase. It is widely used because of its lightweight, small footprint, high extinction ratio, and strong compatibility with optical fiber systems. At present, in the fiber optic gyroscope system and the fiber optic sensing system, it has become the key passive device of polarized light generation in the fiber optic system and it plays an irreplaceable role. Fiber optic polarizers can be divided into fiber optic attenuation polarizers and fiber optic cut-off polarizers. The polarization principle of the former is to enhance the attenuation difference of the two polarization modes. Through the propagation of a certain length, the mode with high propagation loss is eliminated by the loss, thus leaving the other mode with low propagation loss. The polarization principle of the latter is that one polarization mode end and the other pass through. Typical fiber optic polarizers include metal clad fiber optic polarizers ,33, crys2  that are compatible with complementary metal oxide semiconductor (CMOS). Fortunately, graphene is highly compatible with conventional CMOS devices and manufacturing processes ,40,41. K2/Si substrate is mechanically transferred to the core by thermo chemical vapor deposition (CVD). The mask is first etched by using a photolithographic technique, and then the waveguide core is manufactured by modifying it with O2 plasma, in order to obtain a convex linear waveguide with a graphene tape as a core. In the experiment, the optical characteristics of the graphene polarizer based on the air-coated polymer were measured first, and the optical properties of the modified graphene polarizer were then measured again after the polymer resin was spin-coated to form the upper cladding layer. The output port of the waveguide polarizer that they made measured the infrared image according to the degree of polarization. The TE polarized light intensity of the air-clad graphene polarizer is stronger than the TM polarized light intensity. This implies that the key factor for TE-pass polarizers is the air-cladding waveguide. Conversely, the upper layer of the waveguide in the TM-pass polarizer is covered with a UV-curable polymer resin, which modifies the polarized light for a brighter spot. The intensity of TE polarized light is faintly visible. A slab mode can be observed since the RI difference between the upper and lower layers is exceedingly small. This means that the waveguide as a TM-pass polarizer. At the same time, they measured the insertion loss of the waveguide polarizer in order to further explore the characteristics of the conducting mode. Polarization has a significant impact on insertion loss when graphene strips are placed on the waveguide core. For air-coated graphene-based TE-pass polarizers, the average insertion loss of TM and TE polarized light was measured, which were 20.7 Kim first rotated a 203 solution, the graphene film is mechanically transferred to the surface of the glass waveguide. Here, the glass waveguide has also undergone Ag+/Na+ heat exchange [c in order to ensure the true reliability of the PGGM polarizer, and found that the performance of the polarizer will be improved, if μc decreases. The experiment proved that the maximum extinction ratio of the device at the wavelength of 1370 Pei  used polexchange  and end THz technology was first generated in the end of the 19th century and researchers, such as Rubens, have proposed research in this band. In 1974, Fleming formally proposed the term “THz”, which was first used to describe the design of Michelson interference . At thatPolarization manipulation, as one of the most basic characteristics of electromagnetic wave manipulation, has received extensive attention. It has significantly promoted the development of many fields, such as optoelectronics, analytical chemistry, and biology. Traditional methods for realizing polarization operations include photoelastic modulators and optical gratings . AlthougIn 2016, Yu et al.  proposedIn recent years, graphene has been a great success in the field of biological and chemical sensing. Biochemical sensors that are based on graphene and its derivatives have been used to detect various small molecules, including gases molecules, small chemical ions, bacterial and viral cells, and dynamic cellular activity due to the photoelectric properties, biocompatibility of graphene materials, and the ease of biofunctionalization and high specific surface area of graphene derivatives. When compared with previous sensors, these sensors show superior performance in terms of sensitivity, resolution, detection range, and response time . Next, tSurface Plasmon Resonance (SPR) sensing technology is a new sensing technology that was developed in the 1990s. The SPR sensor developed by this technology is a high-resolution optical RI sensor that can be used to detect small changes in RI ,72,73. AIn 2019, Sun et al. designed a highly sensitive polarimetric controlled-modulation plasma biosensor based on monolayer graphene/gold nanoparticles for the direct detection of single-stranded DNA (ssDNA) hybridization . The sys5 pixel/RIU). The experimental results are consistent with the simulation results. Gold nanoparticles are also used as magnifying tags to enhance SPR sensing signals. The coupling between the local SPR of the gold nanoparticles and the propagation-SPR of the gold surface amplifies the SPR response, thus resulting in a significant field enhancement effect. They performed simulations on gold nanoparticles with a diameter of 10 ~ 40 -15 M to 10-7 M of the sensor and the detection limit of 500 aM of the target ssDNA are also shown through DNA hybridization experiments. Sun believes that, when compared with previous DNA detection methods, gold nanoparticle-based biosensors have better application prospects.The SPR sensor that is based on polarization adopts the coupling structure of Kretschmann prism. The SPR system is shown in ficiency . MoreoveThe research on graphene polarization selective absorption is based on the development of prismatic SPR sensors. In recent years, Xing et al. ,85 found storage  and achi storage .1 approaches the critical angle2, the resolution and sensitivity can be improved by using the best thickness of graphene.In the field of sensing, Xing et al. designed a graphene-based optical RI sensor that can accurately detect a small number of cancer cells in normal cells at the single-cell level . RI has medium 2 a.. MediuThe resolution and sensitivity, which are the important parameters of RI sensing, are calculated with the following formula:Among them, S and L represent the sensitivity and resolution of RI sensing, respectively. α is the response of the balanced detector, In summary, this highly sensitive graphene optical sensor enables unlabeled, living, and highly accurate detection of a small number of cancer cells in normal cells at the single-cell level, as well as simultaneous detection and differentiation of two cell lines without separation. It provides an accurate statistical distribution of normal cells and cancer cells with fewer cells. The hypersensitivity and resolution of GSOCS to RI play an important role in promoting the dynamic study of individual cells in the cellular submicro structure. In addition, the high resolution and sensitivity of sensor to RI measurements can be extended to other areas, such as drug discovery, environmental monitoring, and gas- and liquid-phase chemical sensing . The appAs an important branch of sensors, optical fiber sensors integrate signal acquisition and transmission. In addition to the excellent physical properties of the optical fiber itself, its functional characteristics have gradually become apparent with the introduction of new functional materials, such as graphene. Over the past three decades, optic fiber sensors have been used in many fields, such as energy, environment, and biomedicine, due to its unique ability to support biocompatibility. Optical fiber has the properties of anti-electromagnetic interference and atomic radiation, fine diameter, soft quality, light weight mechanical properties, insulation, non-inductive electrical properties, water resistance, high temperature resistance, corrosion resistance chemical properties, and many other excellent properties ,89. MoreFiber optic sensors can be divided into two types according to the sensing principle: one is the light-transmitting sensor and the other is the sensing sensor. In the light-transmitting optical fiber sensor, the optical fiber is only used as a carrier of light and there is no special requirement for the structure of the optical fiber itself. The sensor depends on the direct action of the optical signal to be measured and then calculates the change to be measured by observing the spectral change of the optical signal. In the optical fiber sensor, the optical fiber is only the carrier of the light, and there is no special requirement for the structure of the optical fiber itself. The sensor depends on the direct action of the optical signal to be measured and it calculates the change to be measured by observing the spectral change of the optical signal. This type of sensor is simple in structure, but the physical quantities that can be measured are limited and the sensitivity is low. In the sensing fiber sensor, the fiber is both the main body of the sensor and the medium of signal transmission. Changing the structure of the fiber to increase the type of sensing and sensitivity of the sensor. For example, pulling cone, grating, polishing, and corrosion process the sensing part of the optical fiber. With the development of the diversity of optical fiber structures and the improvement of the precision of sensing detection, graphene-based optical fiber sensors have been developed for research and application. Various graphene fiber optic sensors show significant performance advantages when compared with traditional fiber optic sensors.z/c. As a lager negative imaginary part of In 2014, Wu et al. , for the TM mode . As show TM mode , this ph2 substrate. The SMF with a core diameter of 8 μm was chemically etched to obtain ultra-fine optical fibers with a diameter of d = ~ 10 μm. Among them, the length of the entire fiber tapered portion is approximately ~ 3 cm. Here, the middle of the tapered portion is selected to be coated with graphene, and its length LG is ~ 3 mm. At a wavelength of 1550 nm, the RI of the MgF2 substrate, the cladding of the SMF, and the SMF core were measured, which were 1.37, 1.44, and 1.45, respectively. This research breaks through the application of graphene-based planar waveguides and extends to cylindrical waveguides in the optical field, laying the foundation for the development of fiber devices that are based on graphene polarization characteristics.The team further proposed a graphene multimode fiber interferometer (GMMI) In order to improve the problem of light leakage . The numAs an important part of the optical system, optical modulators are devices used to regulate the basic characteristics of spatial light or waveguide light transmission that is controlled by electrical signals. How to further improve the bandwidth, reduce the half-wave voltage, and improve the modulation efficiency. Meanwhile, on this basis, how further reduce the modulator’s size and interference by external factors has been the research focus of modulator in recent years. When compared with traditional modulators, graphene modulators have the following advantages. First, graphene presents a strong intra-band and inter-band light transition, which has a strong coupling with light, resulting in higher modulation efficiency. Second, graphene has an excellent fast carrier movement rate at room temperature up to 200,000cm2V−1S−1,94, and andwidth . In addiandwidth , he poindulators .At present, further miniaturization limits silicon-based optical devices, which makes it difficult to meet the development requirements of high speed and high broadband. Like silicon-based light modulators, Si crysta does not have linear electro-optic effect, and the secondary electro-optic effect is weak, thus limiting the modulation bandwidth and extinction ratio of the device. Therefore, finding a material with excellent stability and reliability, which is compatible with CMOS technology, and sufficient modulation bandwidth and modulation efficiency has become an important research content of scientists. The emergence of graphene has brought new challenges. It has the characteristics of zero-bandgap band structure and exceedingly high carrier mobility, thus making it a promising application in the field of optical modulation.The unit cell as an absorber, like a graphene double-layered band, only absorbs electromagnetic waves of a specific polarization without affecting cross-polarized waves. Zhang proposed a polarization modulation scheme through electromagnetic wave reflection to further study this characteristic . The pol3N4 layer is d = 10 Si3N4 =1.98, represented by the green area in the The above device adopts the combination of a straight waveguide substrate and graphene, and then adjusts the absorption coefficient of graphene through an electric field to realize the modulation of the device. One of the problems with such structures is that that the interaction between graphene and light field is so weak that the modulation depth is low. The buried waveguide and slit waveguide can theoretically solve this problem. In 2017, Yang et al.  produced3 is one of the most commonly used materials for making M-Z modulators. The effective RI of LiNbO3 waveguide can be changed by adjusting the electric field intensity at both ends of LiNbO3 waveguide when used to make the M-Z modulator because of the first-order electro-optic effect of LiNbO3 material, thus changing the phase difference between the upper and lower arms of the modulator. Subsequently, the intensity of the output light is changed by the interference of the upper and lower arms, and the process of loading the electrical signal into the optical signal is completed. However, the size of the M-Z modulator that is based on LiNbO3 is generally larger, so the traveling wave electrode structure is needed to improve the modulation rate. In addition, the biggest limitation of the LiNbO3 M-Z modulator is that it is difficult to be compatible with existing CMOS processes, which makes integration applications difficult. Thus, people focus their attention on the most commonly used integrated electro-optic device material—silicon. The early silicon-based M-Z modulators were all based on the thermal and optical effect due to the high thermal and optical coefficient of silicon materials. However, such devices are limited by the speed of thermal modulation, so it is difficult to meet the demand of high-speed signal modulation. The modulation rate of the fastest thermosensitive silicon-based modulator published so far is still on the order of microseconds [As a mature electro-optic modulator, M-Z modulator is widely used in analog photonic link. The M-Z modulator is different from the electrical absorption modulator, which depends on the applied voltage to change the absorption spectrum of the material. It mainly uses the linear electro-optic effect to adjust the RI of the material, and then uses the M-Z interferometer structure to make the output optical power change with the applied voltage. In practical applications, LiNbOoseconds . Subsequoseconds  proposed3N4 inside the silicon. Three layers of graphene sheets were placed in Si3N4, and they were separated from each other by 10 3N4 has a greater effect on the GSW effective index  point. In addition, the GSW loss and the real and imaginary parts of In 2013, Yang et al. designed an M-Z modulator that was based on a hybrid graphene silicon waveguide (GSW) that was ultra-fast and compatible with CMOS . As show studies ,106. TheNZ point . For M-ZIn 2015, Hao et al. proposed a polarization modulator that is based on graphene-coated interferometers that is independent of the polarization of incident light . By appl surface , and thene layer ,108. The2/Si was selected as the back gate substrate with Si as the back gate electrode. The first photo graphene photodetector was prepared to realize the super-speed photodetection of graphene [As a kind of photoelectric device sensitive to incident light polarization, polarization-sensitive photodetector has a strong influence in navigation, astronomy , qualitygraphene .2/germanium heterojunction, and enhanced light absorption of the van der Waals heterojunction of mixed size and effective carrier collection of graphene transparent electrode, which exhibited high polarization sensitivity and broadband advantages, including high light responsiveness, high specific detection rateand fast response speed, etc [2, GeSe2, and ReSe2), black phosphorus (BP), and GeAs, exhibit excellent electronic and photoelectrical properties. However, they all have their own drawbacks. For example, the band gap of many TMDCs is usually greater than 1 eV, which is not suitable for infrared detection [Long wave infrared (LWIR) photodetectors have important applications in optical communication, night vision, and many other fields. Polarization is one of the most important properties of light, so polarization sensitive photodetectors have important value in practical LWIR applications. In recent years, various materials with special structures have been proposed to detect polarized light from ultraviolet to infrared light ,112. In eed, etc . Wu noteetection . BP is netection ,116. Theetection . Figure It is still difficult to obtain a graphene photodetector with both high photoelectrical responsiveness and fast response speed, according to the current research situation. It is necessary to consider the normalized geochemical measurement related to noise, photosensitive area and measurement bandwidth. Moreover, while improving the photoelectric responsiveness of the graphene photodetector, it might also reduce its ability to detect wide spectrum. Therefore, the research on improving the performance of graphene photodetectors should be carried out according to the specific application direction.As a new two-dimensional material, graphene has excellent optical and photoelectrical properties. Its spectral response range is extremely wide, achieving full spectral response between ultraviolet and THz bands. Graphene is an ideal optoelectronic material due to its high carrier mobility and ultra-high light response speed . The dev


GRN, TMEM106B and ABCC9 are proposed as LATE‐NC + HS risk factors in brain bank collections. To replicate these results in independent population‐representative cohorts, hippocampal sections from brains donated to three such studies  were stained with hematoxylin–eosin (n = 744) and anti‐pTDP‐43 (n = 713), and evaluated for LATE‐NC + HS and TDP‐43 pathology. Single nucleotide polymorphism genotypes in GRN rs5848, TMEM106B rs1990622 and ABCC9 rs704178 were determined. LATE‐NC + HS (n = 58) was significantly associated with the GRN rs5848 genotype (χ2(2) = 20.61, P < 0.001) and T‐allele (χ2(1) = 21.04, P < 0.001), and TMEM106B rs1990622 genotype  and A‐allele (χ2(1) = 25.75, P < 0.001). No differences in ABCC9 rs704178 genotype or allele frequency were found between LATE‐NC + HS and non‐LATE‐NC + HS neuropathology cases. Dentate gyrus TDP‐43 pathology associated with GRN and TMEM106B variations, but the association with TMEM106B nullified when LATE‐NC + HS cases were excluded. Our results indicate that GRN and TMEM106B are associated with severe loss of CA1 neurons in the aging brain, while ABCC9 was not confirmed as a genetic risk factor for LATE‐NC + HS. The association between TMEM106B and LATE‐NC + HS may be independent of dentate TDP‐43 pathology.Limbic‐predominant age‐related TAR‐DNA‐binding protein‐43 (TDP‐43) encephalopathy with hippocampal sclerosis pathology (LATE‐NC + HS) is a neurodegenerative disorder characterized by severe hippocampal CA1 neuron loss and TDP‐43‐pathology, leading to cognitive dysfunction and dementia. Polymorphisms in  Hippocampal sclerosis in old age is a dementing disorder characterized by severe loss of pyramidal neurons and gliosis in the hippocampal CA1 area. In addition to the anatomically defined neuron loss, hippocampal sclerosis is frequently associated with aggregations of transactive response DNA binding protein 43kDa (TDP‐43) GRN (rs5848) TMEM106B (rs1990622) ABCC9  In three European population based studies of older people with brain donation, two from the UK and one from Finland, 79‐100% LATE‐NC + HS cases were found to have TDP‐43 pathology in the hippocampal dentate gyrus GRN rs5848 TT genotype is associated with lower progranulin levels and has been linked with frontotemporal lobar degeneration with TDP‐43 positive inclusions (FTLD‐TDP) without GRN mutation TMEM106B is reported to modulate progranulin levels ABCC9 has not been associated with FTLD‐TDP, TDP‐43 accumulation or other neurodegenerative diseases than LATE‐NC + HS, and possible mechanisms of ABCC9 variation affecting CA1 neuron loss are unclear GRN rs5848, TMEM106B rs1990622 and ABCC9 rs704178 variants in LATE‐NC + HS have been published. Here, we investigate these proposed risk variations in three population‐representative cohorts of older people, and evaluate their association with LATE‐NC + HS, which could indicate the underlying pathophysiological mechanisms for CA1 neuron loss in the aging brain. We also assess if LATE‐NC without hippocampal sclerosis is associated with the proposed genetic variations.No population‐representative analyses on This study is set within EClipSE , which is a collaboration of the three European population‐representative longitudinal cohort studies with brain donation programs: the Cognitive Function and Ageing Studies (CFAS) , the Cambridge City over‐75s Cohort , and the Vantaa 85+ study . Cohort profiles, recruiting procedures and the approach for brain donation have been described previously in detail In CFAS and CC75C, brains were removed as soon as possible after death and bisected. One hemisphere was then dissected coronally and frozen at − 80°C. The contralateral hemisphere was formalin‐fixed for at least six weeks, cut in coronal plane, and approximately 1‐centimeter (cm)‐thick samples were paraffin‐embedded. In Vantaa 85+, both hemispheres were formalin‐fixed, and dissected coronally. The right hemisphere was sampled for paraffin‐embedding, while samples from the left hemisphere were conserved in polyethylene glycol (PEG). PEG‐conserved hippocampal tissue was reprocessed into paraffin in 2013.Six‐ to nine‐micrometer (µm)‐thick hippocampal sections were stained with hematoxylin–eosin. To standardize the diagnosis of hippocampal sclerosis across all three EClipSE cohorts, available sections were systematically assessed for severe neuron loss by an inter‐rater‐controlled method In CC75C and CFAS, 431/460 samples were available for TDP‐43 assessment, while previous research had exhausted the hippocampal area on the remainder. Nine micrometer hippocampal sections were immunostained with anti‐pTDP‐43 antibody  In Vantaa 85+, 282/284 samples were included in the TDP‐43 assessment. Hippocampal tissue sections (4μm) from the right hemisphere were immunostained with anti‐pTDP‐43 antibodies  Anti‐pTDP‐43 immunoreactive solid neuronal cytoplasmic inclusions (NCI) were evaluated blind to clinical or other pathological information as present or absent in the hippocampal dentate cell layer. In all three cohorts, TDP‐43 assessment was inter‐rater evaluated.LATE‐NC presents with TDP‐43 pathology in the amygdala at stage 1, and in the hippocampus at stage 2. Figure GRN rs5848, TMEM106B rs1990622 and ABCC9 rs704178. Pre‐designed TaqMan SNP Genotype Assays were available from ThermoFischer Scientific. For 19 CC75C subjects, DNA was extracted from paraffin‐embedded blocks, as no frozen tissue was available.Single nucleotide polymorphism (SNP) analysis for CC75C/CFAS was done at the Karolinska Institute, Sweden. A TaqMan SNP 7500 genotyping assay on real time PCR  was used to determine the target SNPs. The target polymorphisms were GRN rs5848 and TMEM106B rs1990622 were determined from whole‐genome sequencing (WGS) data in 150 subjects ABCC9 rs704180 were determined from the WGS data in 150 subjects and the remainder samples were Sanger sequenced for this SNP (data not shown). Genotype for ABCC9 rs704178 was imputed with Beagle 4.1 (version 27Jan18.7e1) using the population‐specific SISu v3 imputation reference panel (https://doi.org/10.17504/protocols.io.nmndc5e). The quality of imputed rs704178 genotypes was high and passed post‐imputation quality control  and 98.6 % concordance between imputed and whole‐genome sequencing‐derived genotypes of internal control samples). The number of subjects with reliable results for each target SNP is reported in Table In the Vantaa 85+ cohort, genotypes of ABCC9 were determined, because the genotype data were not available for recommended reference A/G SNP rs704180 of all three studies. However, these two SNPs are in near perfect linkage disequilibrium.For the EClipSE cohort, G/C SNP rs704178 of gene For CFAS and CC75C samples, TDP‐43 inter‐rater agreement was assessed calculating Gwet's Agreement Coefficient 2 (AC2) using Agreestat 2015.1 . Near‐perfect agreement was reached for all inter‐rater evaluations . For Vantaa 85+ samples, TDP‐43 pathologies were confirmed by a second and a third rater.2(degree of freedom [df])). Chi2 (χ2(df)) (or Fisher's exact test [FET] when appropriate) was used to test the association of genotype or allele frequency and LATE‐NC + HS or TDP‐43 pathology. Each SNP was analyzed using an additive mode of inheritance . ABCC9 rs704178 was furthermore analyzed using a recessive mode of inheritance , as this has previously been shown to be appropriate Hardy–Weinberg equilibrium (HWE) expected frequencies were calculated and tested using Chi2 goodness of fit  were positive for hippocampal dentate NCI, while in the Vantaa 85+ cohort 26 of the 34 hippocampal sclerosis cases with TDP‐43‐immunostained sections presented with dentate NCI. However, in the Vantaa 85+ cohort, hippocampal sclerosis was evaluated bilaterally, whereas TDP‐43 was evaluated only on the right hemisphere. All Vantaa 85+ cases with hippocampal sclerosis pathology on the right hemisphere were positive for dentate TDP‐43 NCI on the ipsilateral side. The eight Vantaa 85+ hippocampal sclerosis cases which were negative for dentate TDP‐43 NCI presented with unilateral hippocampal sclerosis on the left hemisphere. Therefore, these cases cannot be considered as dentate TDP‐43 NCI negative, and all hippocampal sclerosis cases in the EClipSE cohort are referred to as LATE‐NC + HS in this study.GRN, TMEM106B and ABCC9 genotype frequencies, as well as LATE‐NC + HS and dentate TDP‐43 NCI prevalence for the EClipSE cohort. The genotype frequencies did not deviate from HWE.Table GRN rs5848 genotype in EClipSE cohorts (χ2(2) = 20.61, P < 0.001, phi = 0.169), presenting more frequently with C/T and T/T genotypes compared to the remainder population (Table P < 0.001). LATE‐NC + HS cases were significantly associated with the risk‐allele T in the EClipSE cohorts (χ2(1) = 21.04, P < 0.001, phi = 0.121).LATE‐NC + HS associated significantly with the TMEM106B genotype in EClipSE . LATE‐NC + HS cases presented more frequently with the genotype A/A than the remainder population (χ2(1) = 25.75, P < 0.001, phi = 0.123, Table LATE‐NC + HS was significantly associated with the ABCC9 rs704178 genotype or allele frequency, irrespective of the analyzed mode of inheritance (additive or recessive) .LATE‐NC + HS did not differ from the remainder population in e) Table . ControlGRN rs5848 genotypes T/C and T/T (χ2(2) = 18.59, P < 0.001, phi = 0.164), also when controlling for sex and age at death in logistic regression , and the T‐allele (χ2(1) = 17.01, P < 0.001, phi = 0.111). Dentate TDP‐43 NCI was also significantly associated with the TMEM106B rs1990622 genotype A/A (χ2(2) = 10.33, P = 0.006, phi = 0.123), even when accounted for sex and age at death , and the A‐allele (χ2(1) = 10.47, P = 0.001, phi = 0.088) .Presence of dentate TDP‐43 NCI was significantly associated with the As all LATE‐NC + HS cases were of TDP‐43 positive or unknown status ipsilateral to the hippocampal sclerosis pathology, analyses on the association of dentate TDP‐43 NCI and LATE‐NC + HS risk genes were not conducted stratified by LATE‐NC + HS.GRN rs5848 genotypes T/C and T/T (χ2(2) = 7.99, P = 0.018, phi = 0.112) and the GRN rs5848 T‐allele (χ2(1) = 7.6, P = 0.006, phi = 0.077)  Table , but thees Table .GRN, TMEM106B and ABCC9 genes are associated with hippocampal sclerosis in old age/LATE‐NC + HS, but to date no population‐representative data have been published. Here, we studied three European population‐representative cohorts and confirmed an association of LATE‐NC + HS with polymorphisms in GRN and TMEM106B. The published association of LATE‐NC + HS with ABCC9 polymorphism could not be reproduced. These detected associations of GRN and TMEM106B with LATE‐NC + HS may be related to progranulin expression, as literature suggests both GRN and TMEM106B polymorphisms to be associated with variation in progranulin levels.Previous research, based on US brain bank collections drawing on volunteer and clinical dementia cohorts, has indicated that polymorphisms in ABCC9 locus must therefore be interpreted with caution. However, as our population‐representative study results give very strong independent support to the previously reported associations between LATE‐NC + HS and the polymorphic sites in GRN and TMEM106B, it seems likely that functions of these two genes indeed do affect survival of the CA1 neurons, at least in older individuals. On the other hand, to confirm the hypothesis that variations in GRN and TMEM106B contribute to LATE‐NC + HS neuron loss by altered progranulin levels, further studies would need to assess the expression of progranulin in association with LATE‐NC + HS.Limitations of this study include the overall cohort's sample size, different TDP‐43 antibodies and section thickness between the UK and Finnish cohorts, unilateral instead of bilateral assessment of hippocampal sclerosis in the UK studies and of TDP‐43 in all three cohorts, as well as lack of proof of causality. It is likely that we did not capture all LATE‐NC cases in these cohorts as TDP‐43 presence was only evaluated unilaterally in the hippocampal dentate. Further, not all hippocampal sclerosis cases could be verified as LATE‐NC as TDP‐43 staining was not available for each. Even though the EClipSE collaboration is the largest population‐representative epidemiological cohort with brain donation, numbers of LATE‐NC + HS cases may still be low for a genetic study. The lack of confirmation of the GRN, TMEM106B and ABCC9 as risk factors for LATE‐NC + HS, obtained cases from brain banks and Alzheimer's Disease Centers Important strengths of this study are the high mean age and population‐representative origin of the cohorts, introducing minimal selection bias. Studies that previously reported polymorphisms in GRN at chromosome 17) is universally expressed in the central nervous system (CNS) during early neuronal development, and is also expressed at modest levels in neurons and microglia in adults GRN mutations causing FTLD‐TDP have been reported to create null alleles via haploinsufficiency mechanism, resulting in reduced protein levels GRN, which is associated with variations in progranulin levels and increased risk of LATE‐NC + HS, is also part of a binding site for microRNA miR‐659 GRN‐null mutations Progranulin (encoded by gene TMEM106B (at chromosome 7p21) encodes a transmembrane protein, with a preferential expression in the frontal lobe TMEM106B may specifically modify the development of FTLD in the presence of a GRN mutation TMEM106B rs1990622 variant, where the C allele regulates GRN expression GRN rs5848 and TMEM106B rs1990622 to be associated with LATE‐NC + HS. Reduced progranulin levels could increase the vulnerability of specific CA1 neuron populations, through higher susceptibility for stress and inflammatory changes. As all LATE‐NC + HS cases presented with ipsilateral dentate TDP‐43 NCI, it was not possible to analyze the association between LATE‐NC + HS and the risk genes independent of TDP‐43. However, the association between TMEM106B and dentate TDP‐43 NCI was nullified when LATE‐NC + HS cases were excluded from the analyses, which indicates that the association between LATE‐NC + HS and TMEM106B is dependent on LATE‐NC + HS.Gene GRN rs5848, TMEM106B rs1990622 and progranulin levels/lysosomal pathways on neurodegeneration were largely based on younger people than those who are at greatest risk of LATE‐NC + HS Previous studies evaluating the effect of ABCC9 gene encodes an evolutionarily conserved large polypeptide sulfonylurea receptor 2 (SUR2) with multiple membrane‐spanning domains and multiple levels of biologic complexity ABCC9 have been associated with a risk for human brain illnesses, including sleep disturbances and LATE‐NC + HS ABCC9 is also an expression quantitative trait locus, which affects the levels and splice variants of brain mRNA transcripts derived from ABCC9ABCC9 rs704178 genotype  or allele.ABCC9 rs704178 was also not associated with TDP‐43 pathology in these cohorts. It is possible that differences in the cohort selection and case definition explain the discrepancy. It is also possible that sex could influence the findings, since men at this age are a minority of the population and power is therefore limited to test for sex differences. Findings by Nelson et al were not adjusted for sex et al were adjusted ABCC9 variation is unclear, and this study did not replicate the previous results. Further studies on ABCC9 and LATE‐NC + HS from different source populations are needed to confirm the lack or verify the association.The previously reported GRN rs5848 C/T and T/T as well as TMEM106B rs1990622 A/A genotype are associated with loss of CA1 neurons in the aging brain, supporting a possible link through lower progranulin levels. ABCC9 rs704178, however, was not confirmed as a genetic risk factor of LATE‐NC + HS.In conclusion, this study confirmed in population‐representative cohorts that The authors declare no conflict of interest.Suvi R. K. Hokkanen: Designed this study with MK, conducted neuropathological evaluation of hippocampal sclerosis in the EClipSE cohorts, performed SNP analyses for the CC75C and CFAS cohorts, evaluated TDP‐43 pathology in half of the CFAS cohort, inter‐rater evaluated TDP‐43 pathology in CC75C and half of the CFAS cohort, conducted the statistical analyses except inter‐rater analysis, drafted and revised the manuscript. Mia Kero: Study design with SRKH, inter‐rater evaluated hippocampal sclerosis pathology in the Vantaa 85+ cohort, innovation and processing of PEG‐embedded blocks into FFPE‐blocks, optimization and staining of TDP‐43 staining, evaluating TDP‐43 pathology in Vantaa 85+, sequence data analysis guided by KK, preliminary statistical analyses for Vantaa 85+, drafted and revised the manuscript. Karri Kaivola: Gene sequencing and sequencing data analysis, guiding MK with sequencing data analysis and revised the manuscript. Sally Hunter: Conducted neuropathological evaluation of TDP‐43 pathology in the CC75C and half of CFAS cohort, inter‐rater evaluated TDP‐43 pathology in half of the CFAS cohort, inter‐rater evaluated hippocampal sclerosis evaluation in CFAS and CC75C, contributed to the draft and final manuscript. Hannah A. D. Keage: Performed the inter‐rater analysis, secured project funding, and contributed to the draft and final manuscript. Anna Kiviharju: Gene sequencing and sequencing data analysis in the Vantaa 85+ cohort. Anna Raunio: Material collection partly for sequencing, optimization and staining of TDP‐43 together with MK in the Vantaa 85+ cohort. Pentti J. Tienari: Sequencing data acquisition in the Vantaa 85+ cohort, secured project funding and critical revision of the manuscript. Anders Paetau: Inter‐rater evaluated TDP‐43 pathology with MK in the Vantaa 85+ cohort and critical revision of the manuscript. Fiona E. Matthews: Secured project funding, contributed to the draft and final manuscript. Jane Fleming: Coordination of the CC75C study, contributed to the final manuscript. Caroline Graff: Provided guidance on the SNP analyses of the CFAS and CC75C cohort, contributed to the draft and final manuscript. Tuomo M. Polvikoski: Baseline patient material collection for Vantaa 85+ study, verified neuropathological evaluation of hippocampal sclerosis cases in the EClipSE cohort, and contributed to the draft and revised the manuscript. Liisa Myllykangas: Study design, critical revision of the manuscript, secured project funding, supervising Vantaa 85+ work of this EClipSE collaboration study. Carol Brayne: Secured project funding, contributed to the draft and final manuscript. The EClipSE collaboration designed the cohort studies, generated additional data, and revised the manuscript.Figure S1. A: Section of hippocampus showing dentate, molecular layer and CA1 from a case with severe dentate neuronal inclusions but minimal cell loss in CA1; B: CA1 from same slide showing very few pathologies immunoreactive for anti‐phosphorylated TDP‐43 antibody; C: Dentate from same slide showing a range of pathologies immunoreactive for anti‐phosphorylated TDP‐43 antibody including cytoplasmic inclusions and neurites. D: Section of hippocampus showing dentate, molecular layer and CA1 from a case with severe dentate neuronal inclusions and severe cell loss in CA1 qualifying as HScl; E: CA1 from same slide showing few pathologies immunoreactive for anti‐phosphorylated TDP‐43 antibody; F: Dentate from same slide showing a range of pathologies immunoreactive for anti‐phosphorylated TDP‐43 antibody including cytoplasmic inclusions and neurites. Scale bars: A, D = 200 μm, B, C, E, F = 50 μm.Table S1. Association of GRN rs5848, TMEM106B rs1990622 and ABCC9 rs704178 with dentate TDP‐43 solid neuronal inclusions in subjects without LATE‐NC+HS.Click here for additional data file. Click here for additional data file. Click here for additional data file.


The data revealed the consistency of the time spent (4.86 ± 0.98 s) and breakout distance (6.04 ± 0.94 m) among the four turning techniques, and no differences were observed between them regarding time and average velocity up to 7.5 m. The hydrodynamic characteristics and pull-out strategy of the backstroke-to-breaststroke turns performed by the age group swimmers were independent of the selected technique.We compared the hydrodynamic characteristics and pull-out strategies of four backstroke-to-breaststroke turning techniques in young swimmers. Eighteen 11 and 12-year-old swimmers participated in a 4 week intervention program including 16 contextual interference sessions. The hydrodynamic variables were assessed through inverse dynamics, and the pull-out strategy kinematics were assessed with tracking markers followed by 12 land cameras and 11 underwater cameras. Swimmers randomly completed sixteen 30 m maximal backstroke-to breaststroke-open, somersault, bucket and crossover turns (four in each technique) with a 3 min rest. The data showed higher drag force, cross-sectional area and drag coefficient values for the first (compared with the second) gliding position. The crossover turn revealed the highest push-off velocity (2.17 ± 0.05 m·s Turning performance is determined by the efficiency of changing direction while swimming between the turn-in and turn-out phases. Consequently, swimmers should approach the wall by maintaining speed without compromising the ability to turn and push off the wall as powerfully as possible  ,2,3. TheD) can be attributed to varying body dimensions or to changes in body position [D) and cross-sectional area (S) of the first gliding position were lower than those of the second gliding path [Theoretically, swimmers can improve their turn-out performance by improving their underwater gliding efficiency, both minimizing drag and optimizing underwater timing and distance . When glposition ,12. Dp cposition ,13 or thposition  and numeposition ,15,16. Ting path ,16. Howeing path ,15,17.Gliding performance depends on the initial velocity, as well as the deceleration magnitude and its duration . FurtherThe key mechanical features of the four studied backstroke-to-breaststroke turn techniques, considering the hydrodynamics and pull-out strategy, were obtained after intervention training sessions. Those key mechanical features were described and compared using selected kinematic and hydrodynamic factors. Four backstroke-to-breaststroke turns were identified, based on FINA rules SW 6.5 and 9.4 and the complex movement variations that specify body configuration and orientation in the rotation and push-off phases . A 4 weeSwimmers followed a block-type schedule plan from the first to the fourth practice sessions (each focusing on a different turning technique), and a serial schedule was followed from the fifth to the eighth session . A serial schedule was also followed from the ninth to the twelfth session . Then, a random schedule was followed from the thirteenth to the sixteenth sessions, with an equal number of trials for each technique. Following the intervention period, swimmers randomly performed twelve repetitions, those being three repetitions of each turning technique . The trials started and finished from the middle of the pool, with swimmers performing turns in and out of the wall at maximum speed until the 15 m reference. An experienced researcher observed every turn and asked swimmers to repeat those not properly performed. The average values  obtained for each selected variable per turning technique were taken for posterior analysis.−2 body mass index, 15.93 ± 1.81 and 18.06 ± 1.41% of fat mass, 158.50 ± 3.89 and 149.28 ± 2.71 cm in height, 157.82 ± 4.06 and 151.00 ± 2.67 cm arm span, 183.73 ± 5.60 and 192.38 ± 5.45 s 200 m individual medley short course best performance (representing 61.89 ± 8.69% and 67.56 ± 6.19% of the world junior record) and 3.56 ± 1.43 and 3.12 ± 1.13 years of competitive experience, and both were in Tanner stages 2–4. Swimmers, coaches and parents were informed of the investigation benefits and risks before signing an informed consent form to participate. The study was approved by the ethics board of the institution (code n° CEFADE 08.2014), and all procedures were in accordance with the Declaration of Helsinki.Eighteen age group swimmers  participated in the study. Their main anthropometric, performance and training background characteristic means and standard deviations values were  as follows: 12.45 ± 0.16 and 11.71 ± 0.18 years of age, 48.81 ± 3.57 and 43.47 ± 3.40 kg of body mass, 19.65 ± 0.77 and 18.97 ± 0.90 kg/mSubjects were photographed using scaled photographs ,14 at a 3 and locations of 10 m , 2.0 m  and 1.5 m  were obtained. The origin of the referential system was set by using four points of reflective markers at the wall , and the calibration mean precision value obtained was ~0.79 mm. Marker reconstruction accuracy reached 93.2%.Calibration was first performed with a static L-frame . Then, wand dynamic calibration was conducted using an L-shaped reference structure and moving a wand with two markers of 0.7495 m of interpoint distance (according to the manufacturer recommendations). Wand dynamic calibrations were performed separately underwater and overwater, and they were combined by merging a land-based and underwater system using dual media wand movements . A calibD and S as previously proposed [The hydrodynamic variables were assessed through inverse dynamics, considering D, Cproposed ,16. D waD for each gliding was calculated using the following transformation:−3), S is the typical cross-section frontal area surface of the first and second gliding positions and v is the swimmer velocity relative to the flow [® 2014a  as the summation of the triangles’ areas [The acceleration-to-time curve (a(t)) of the sacrum reflective marker was assessed during the first and second glides of the pull-out phase through numerical differentiation of the v(t) curve (filtered with a fourth-order Butterworth filter). The Cthe flow ,16. S wathe flow ,14,16 anTo determine the turn-out performance, it was necessary to examine the variation and relationships of the featured variables with factors possibly affecting the response to pull-out performance. Qualisys Track Manager  software was used to acquire the 3D kinematic data see d, which 2) measurement was adopted [After applying a Shapiro–Wilk normality test, mean and standard deviation computations for descriptive analysis were obtained for all variables. Sphericity was verified using the Bartlett test before using repeated ANOVA measures to detect any main effect of the hydrodynamics characteristics, pull-out strategy or the four backstroke and breaststroke turning techniques. Provided that a significant effect was found, Bonferroni post hoc analysis was conducted for each pairwise comparison. To provide an unbiased estimate of the population effect size, a partial omega squared . The other hydrodynamic characteristics of the first and second gliding positions at the open, somersault, bucket and crossover backstroke-to-breaststroke turning techniques are displayed in D values compared with the first one. The results demonstrate that there were no main effects of the turns on S, D and CD among the four turning techniques.The S of the second gliding was higher than the first gliding . However, there are possible explanations for the obtained results, allowing one to better understand the hydrodynamic characteristics and pull-out strategies used by young swimmers.2) [D and v), no differences were found among the four studied turns in the two gliding positions. Our findings confirmed the previous results, which suggested that D was associated with anthropometric differences with respect to age and body alignments [−1, respectively) [−1) [Our swimmers’ S values in both the first and second gliding positions were relatively low when compared with the data from national level swimmers (740.42 ± 101.89 and 784.25 ± 99.62 cm2) . Regardiignments ,25. In tctively) ,27,28, bThe higher push-off velocity values observed in the crossover turn could be due to the rotational skills of  and lateAs was already shown, the pull-out strategy optimization can substantially impact swimming turn performance, with a properly executed streamlined posture, gliding depth and optimal underwater lower and upper limb action timing and distance being key factors for turn-out performance ,12. The D in the second gliding (than in the first position), there was a tendency for the swimmer’s average velocity to decrease, in line with the findings of Termin and Pendergast [Choosing the correct gliding duration and distance, as well as a proper lower limb action timing, for maximizing velocity should be an individual strategy. The current data showed that for all the studied turning techniques, swimmers spent ~1.21–1.34 s covering the 2.41–2.60 m first gliding distance before initiating the transition, corroborating the values proposed by Lyttle et al. . In factndergast  that theNonetheless, in spite of the current study’s interesting findings, there are some limitations that should be considered and addressed in future research. A correctly done underwater phase generally incorporates pushing off the wall, good streamlining and initiating transition at the appropriate time, but we only focused on the kinematics of the first component . Consequently, an integrative analysis combining the kinematic and kinetic characteristics of pushing off the wall associated with the turn-out strategy hydrodynamic variables should be incorporated in future research. Our age group swimmers were pooled for evaluation (in consideration of a reasonable sample size) with gender differences not being considered. We feel that swimmers should be analyzed by sex in future research, particularly if samples with swimmers after puberty are used. Last but not least, a control group should be added in future studies, allowing for the minimization of random effects on dependent variables over time and obtaining stronger experimental research designs.D), as well as the pull-out strategy, were similar in the age group swimmers, irrespective of the backstroke-to-breaststroke turning technique used. Taken together with previous recommendations available in the literature, these findings highlight that optimizing propulsion during push-off, the glide depth, limb actions during transition (without decreasing velocity) and distance and time optimization could directly influence turn-out performance. We are confident that the current data is useful and will serve as a base for future studies centred on the relationship between biomechanical variables and how a change in hydrodynamic characteristics and pull-out strategy can provide a better understanding of the most efficient backstroke-to-breaststroke turns.The hydrodynamic characteristics (such as S, D and C