During vestibular schwannoma surgery there is a risk of endolymphatic duct and sac injury, which may cause a loss or a deterioration of hearing. The goal of the study was to evaluate the empirical utility of presurgical planning using CT with the bone window for the hearing preservation surgery.The study was performed on 14 human temporal bones. CT scans with the bone window were obtained in the standard position. Safe drilling line was evaluated and after that drilling distances were analysed: the lateral drilling distance, total length of internal acoustic meatus, drilled length of internal acoustic meatus. After this, a surgical exposure was performed, using size of a drill tip as measuring scale. The dura was excised and endolymphatic duct was injected with a latex. Revision of the internal acoustic meatus was performed with the use of a microscope.Mean results of safe drilling coefficients were: lateral drilling distance: 10 ± 2 mm, total length of internal acoustic meatus: 9 ± 2 mm, drilled length of internal acoustic meatus: 7 ± 2 mm. In all cases, no endolymphatic duct injury was observed.Preoperative radiological planning using the safe drilling coefficients is of value for the hearing preservation surgery in vestibular schwannoma. The size of the drilling tip may be used as an intraoperative measuring scale during this procedure. However, CT with a bone window is a necessary tool for the purposes of this procedure. Hearing preservation is one of the goals during the surgery of vestibular schwannoma (VS). It is achievable through a suboccipital retrosigmoid approach, when the preoperative hearing was determined as usable. This aim is fulfilled even in 51 %  and depeIn the study, 14 specimens of human temporal bones  covered with dura and with natural contents of the bony canals were used. None of the specimens had a visible pathology. All examinations were performed on the Toshiba Aquilion 64 CT Scanner. Samples were placed in a neutral position similar to the standard examination of that area for clinical purposes. Coordinates were established on the ‘temporal bone’ preset, with the slide thickness of 0.5 mm. After this, the radiological analysis was performed with the use of the eFilm™ Lite™ software. The preoperative planning needed measurements as described below in two steps. Posterior wall of a temporal bone was analysed regarding ED topography. The medialmost point of ED was considered as a lateral limitation of area of safe drilling. Next, from this point the line was drawn rearward to meet a point of standard dural incision—2 cm medial to the edge of sulcus of sigmoid sinus (SSS) [Thanks to SDL we designed some parameters to provide a valuable information for the neurosurgeon about the safe distance of drilling. First of them—the lateral limitation of the posterior wall of petrous bone (LL) was a distance from the posterior margin of internal acoustic porus (PMP) to the SDL Fig. . The secAfter the planning, a bone specimen was placed in a special holder in position similar to the one observed in the surgical field. The angle of approach was set to 25°, which was based on previous measurements between SDL and the surface of posterior wall of petrous bone. Using an intraoperative microscope, a dura mater was cut in the standard fashion on the length of LL .The drilling was intentionally conducted according to previous radiological distances to assess their accuracy. All the measured distances are presented in Table A microscopic inspection of a drilled area revealed no ED injury in all of the cases Fig. . InsteadThe relation of ES and ED to adjacent vascular and bony elements has been discussed in the literature , 11. TheClinical observations prove a hearing preservation to be one of the most challenging targets to achieve during the VS surgery. The outcome, however, may not be satisfactory in long-term observation. In some of published case series, the deterioration of hearing was reported regardless the size of a tumour and despite the preservation of usable hearing during surgery. Betchen et al.  analysedOne of the hypotheses puts an emphasis on the significance of preserving the ED during IAM drilling. Sulman et al.  dissecteA study we performed allows in our opinion to prove the accuracy of radiological preoperative assessment. Although it does not provide arbitrary values for safe IAM drilling, which results from a limited number of specimens, it presents a spectrum of parameters and coefficients that can be used during planning. The evaluation of the safe drilling area seems to be crucial for operative technique, as scheduled distances create conditions for larger and safer exploration of the IAM. However, every approach needs to be set accordingly to individual anatomical configuration. Therefore, the accuracy of radiological measurements proved in direct anatomical reassessment, in our opinion makes CT a mandatory diagnostic tool before every VS surgery.The study revealed that the described methodology of the CT analysis is useful in evaluating the drilling area where there is no risk of an ED injury. The accuracy of performed measurements was assessed empirically and in our opinion preoperative planning should be mandatory for the hearing preservation VS surgery. A CT with a bone window should be an obligatory examination, because it provides a crucial information for a safe and uncomplicated VS resection.


Of all aspects of education mentioned, Cummings’ reported views on genetics were commented upon most frequently and were subject to the most opposition from commenters, but also the most support. Findings offer some insight into the challenges involved in conducting public discourse about the relevance of genes in education. We discuss the accuracy with which Cummings’ views were presented and the effect this may have had on reader responses to the points being raised.An article published in the UK Guardian on 11/10/2013 with the headline ‘Genetics outweighs teaching, Gove advisor tells his boss’ reported a leaked document written by special advisor Dominic Cummings to the then UK Secretary of State for Education, Michael Gove. The article generated 3008 on-line reader comments from the public. These reader comments offer a naturalistic opportunity to understand public opinion regarding Cummings’ controversial suggestions and ideas. We conducted a content analysis of  For reasons both historical and conceptual, genetic science is often misunderstood by the general public Tabery . There iGuardian with the headline ‘Genetics outweighs teaching, Gove advisor tells his boss’. The article reported a leaked essay written by special advisor Dominic Cummings to the then UK Secretary of State for Education, Michael Gove. It reported Cummings’ views on the influence of genes on academic achievement and his view of teacher quality in the UK. It also focused on his opinion that government initiatives such as Sure Start had failed and that UK Higher Education lacked credibility  citing a heritability estimate of 70 % for phonics at ages 7 and 12  identify particular genes associated with general cognitive ability (g), something that is beginning to happen now but is still very much in its infancy . However, this does not mean that achievement is genetically determined, or that teachers don’t matter, both of which the article implied: ‘Cummings maintains that individual child performance is mainly based on genetics and a child’s IQ rather than the quality of teaching’ .The  Wintour . CummingGuardian at the same time this article received a particularly large response. For example, an article published 8 days later, detailing an attack by the Liberal Democrats on Michael Gove’s new school reforms received n = 1161 comments . The Commission found, using a sample of >1000 UK citizens, that the vast majority of people agreed that genetic technology can be used to diagnose and cure disease. The vast majority also supported the use of genetic technology in solving crimes and finding perpetrators.Those with better knowledge of genetics were more likely to be supportive of the role of genetics and the use of genetic technology in a medical role. Most relevant to the current study is the finding that, when asked whether they thought nature or nurture determined intelligence, the general public tended to see a 50/50 split in influence  is politically left-leaning and the advisor is associated with a right-wing political party (The Conservatives). Moreover, the reporting of the antagonistic nature of the advisors’ comments was likely to prompt comments from those with strong adversarial reactions who wished to air their views.This hypothesis is based on the fact that the newspaper .This is likely because of the diversity of the sample  and the range of different perspectives, knowledge bases and viewpoints likely to be represented.Hypotheses were as follows:Overall, the aim of the current study is to provide new insight into spontaneous public reactions to the idea of embracing genetics as a relevant consideration in the planning and delivery of education. At a time when genetic research into factors such as intelligence and educational attainment is gathering pace, at both the behavioural and the molecular level,  were copied and pasted into a chart with each comment being assigned an identification number. It was subsequently decided to bolster the sample through the inclusion of a further 75 comments from each of pages 2, 5, 8 and 11 in order to create a final sample of Prior to analysis a coding framework was developed. The decision to include particular codes was driven by the primary purpose of the study–to take the opportunity to gain an insight into the general public’s perceptions of genetics in education. A deductive approach was therefore taken in line with this specific focus.In order to be able to compare the amount of discussion of genetics with other topics also raised in the article it was necessary to include codes relating to all of the main themes mentioned . In order to be able to gauge the amount of discussion and debate that occurred between participants, to help gauge the relative level of controversy surrounding genetics, codes for comments between participants on relevant topics were also necessary. A final group of organisational codes was created to help the research team to gain a sense of comments that were not directly relevant to the research aims.After a small amount of alteration and the addition of two new codes  that emerged after coding began, the final list of codes was established and is shown in Table Once the coding framework was established a single researcher carefully read and coded each individual reader comment. Every comment was also assigned a code showing whether it was an original comment directed at the article or a thread (i.e. a comment directed at another user’s comment). On the whole, comments tended to fit into at least two coding categories.Once the first researcher had assigned codes to all of the 800 comments sampled, it was necessary to check that coding was reliable. A second researcher coded a proportion of the data for the purpose of checking inter-rater reliability. This researcher read the original source (the online news article) and discussed it with the first researcher in order to become familiar with the context. The coding framework was then introduced and the researcher was asked to focus on coding comments for the nine most salient codes, those relating directly to the research questions . Ten percent of the sample (80 comments) were coded independently in this way and both coders’ decisions were entered into SPSS in order to assess inter-rater reliability.n = 8) to the original coding were made, based on differences between coders. This reconciliation and reflection stage  that are of real interest and relevance to the current study.Within the sample there was an almost equal split between comments that were original comments directed at the article (52 %) and comments that were threads (48 %), that is, comments directed at another comment. It was found that 34 % of reader comments in the sample contained unrelated information  or were grammar/fact corrections that expressed no relevant opinion. It is important to bear this in mind as it is the remaining 66 % of reader comments  did not clearly express support for Cumming’s reported view on any topic. This left 10.6 % (n = 85 comments) which expressed specific support for his view, as presented in the article, on at least one topic. We see that genetics received the most comments with 7 % (n = 56) of the overall sample specifically supporting Cummings’ reported views. His views on teaching quality generated 20 comments (2.5 % of sample) showing support for his position. His view on government initiatives generated only four supportive comments (0.5 % of sample) and on higher education just 5 (0.6 % of sample). It is worth noting that overall support for the general content and tone of the article and specific support for a particular topic were coded separately. It was possible for a commenter to agree with Cummings on an individual topic but to express overall disagreement with his position, and vice versa , results showed a clear focus on genetics as the ‘hottest’ topic of discussion among reader comments. Overall, however, 89.4 % of sampled comments (n = 552 comments) did not clearly express opposition to a particular topic mentioned in the article. This left 31 % (n = 248 comments) which specifically opposed one or more of Cummings’ specific views. Once again we see that genetics received the most comments with 23 % of the sample (n = 184 comments) specifically opposing his reported views on genetics. Teaching quality received 5 % (n = 40) of overall comments showing clear opposition towards Cummings’ reported views, government initiative opposition only 2 % (n = 16) and higher education just 1 % (n = 8). It is clear that Cummings’ reported views generated more opposition than they did support.The proportion of those agreeing with Cummings’ reported views on genetics was double that of the second most supported topic–teaching quality. A similar pattern was seen in comments which expressed clear opposition to Cummings’ reported view on one of these topics. Percentage breakdowns regarding expressed opposition to Cummings’ reported views are displayed in Fig. The next step was to look at the amount of agreement and disagreement between reader comments, that is, in threads in which readers responded to each others’ views rather than directly to the article. For this purpose, two codes for agreement and two codes for disagreement were combined. Commenters that either agreed with other commenters who expressed support for Cummings’ views, or disagreed with commenters expressing disagreement, were combined and coded as being ‘in agreement’ with Cummings. Conversely, commenters that either agreed with others who expressed disagreement with Cummings, or disagreed with supportive comments, were coded as ‘disagreeing’ with Cummings’ view. On this basis, 10 % of threads suggested overall opposition to the article and 3.3 % suggested overall support Table .Table 4DOriginal comment:‘Ridiculous, genetics may be a starting point but anyone (except those with brain damage/seriously disabled) can become as good as someone else if they have the proper opportunities and try hard.’Response on thread:‘Think about the people you have met over the years. Is this really true?’An example of a thread in which a commenter disagreed with a previous commenter who, in turn, had disagreed with Cummings’ reported view is shown here for illustrative purposes:n = 54) made a clear reference to Nazis or eugenics in their response to the article. On the whole these references suggested that Cummings’ reported views about genetics in education were comparable to Nazi ideology. For example:‘In the 30’s they called this Eugenics, and it was part of the nazi education. Oooops’‘Yes it seems to be verging more than a little into ‘master race’ territory.’Finally, it is worth noting that 6.8 % of reader comments  almost all did so as a criticism of Cummings, or an expression of fear. The shadow of eugenics remains clear.The results of this content analysis clearly indicate that even when included as just one of a range of potentially controversial educational topics, genetics evokes a disproportionate amount of debate, as argued by others  fear a link between genetic determinism and discrimination. In this article we see a prime example of over-simplification of science leading to hostility and misconceptions from the general public, particularly in a field such as education which the majority of the British public value and place great importance on. We perhaps also see the damage that can be done by having newspaper headlines written to be attention grabbing rather than to accurately represent the content of the article.From the limited literature on public perspectives on genetics in education, the current findings make sense. A lack of knowledge and understanding can often lead to hostility on a complex subject like genetics Tabery . Moreoven = 763 comments (James The high number of comments (and threads) generated by this article illustrates the amount of discussion and debate that this article generated. For comparison, a related article that subsequently appeared in the Guardian, also talking about the role of genetics in education with the word ‘genes’ in the headline but from a pro-nurture stance, received only ts James . It is ats James .It was also interesting to note the occurrence of reader comments related to Nazis, Hitler and eugenics. On the whole these were used as an expression of disagreement or anger at Cummings’ comments on genetics in education. Although these reader comments demonstrate the strength of disagreement and anger felt by some readers they perhaps also suggest a misunderstanding or lack of knowledge of the difference between the suggestion that genetics plays an important role in learning abilities and achievement (as suggested by Cummings) and the misuse and abuse of genetics for harm by the Nazis. This lack of knowledge, prevalence of misunderstanding, hostility and fear around genetics was one of the key points to emerge from the literature Condit  so it isDue to the politically partisan nature of the newspaper in which the article was published, and some emotive and misleading reporting, the generalisability of these findings are limited. It could be argued (with the advisor working for a right wing party) that such hostile reactions were to be expected. Although this must be taken into account it remains unknown what sort of reaction might be received in another newspaper. Given the divisive nature of the topic it seems likely that, even if Cummings’ comments been reported in a right wing newspaper, reactions would have been mixed. It would be interesting to test this hypothesis in future research with a relevant article.We cannot say that the views represented in the sample are those of the UK population at large but they do represent a snapshot of how a large (self-selecting) sample of the general public reacted to a story suggesting a deterministic view of genetics in education. The inclusion of the misconstrued statement that ‘genetics outweighs teaching’ is also likely to have drawn commentators who had a specific interest in the role of genetics in education or a vested interested in teaching.Directions for future research could involve a comparative analysis of reader comments from related sources. For instance, analysis of a similar article in a more right-wing newspaper could provide a valuable insight into potential differences in public opinion based on political allegiance. Analysis of an article in favour of environmental determinism in a left-leaning paper could also prove interesting and the James  article Overall, findings from this study contribute to the currently limited picture of how the general public feel about the potential application of genetics in an educational context. The data suggest that, as predicted, this topic evokes particularly strong feelings and that at least some opposition may be based on misunderstanding. More commenters disagreed than agreed with the views expressed by Cummings, in spite of the empirical evidence supporting any statement that genes play a substantial role in explaining individual differences in academic achievement (</ = 50 %) and that, although environmental factors (and measurement error) explain all of the remaining variance, teaching is just one aspect of the child’s environment that also includes society, school, home and even prenatal environments (Turkheimer


By employing the method of optically detected magnetic resonance, we were thus able to verify that the investigated centres are actually created from the 15N isotopes. We also show that this method is compatible with lithography techniques using e-beam resist, as demonstrated by the implantation of lines using PMMA.Established techniques for ion implantation rely on technically advanced and costly machines like particle accelerators that only few research groups possess. We report here about a new and surprisingly simple ion implantation method that is based upon a widespread laboratory instrument: The scanning electron microscope. We show that it can be utilized to ionize atoms and molecules from the restgas by collisions with electrons of the beam and subsequently accelerate and implant them into an insulating sample by the effect of a potential building up at the sample surface. Our method is demonstrated by the implantation of nitrogen ions into diamond and their subsequent conversion to nitrogen vacancy centres which can be easily measured by fluorescence confocal microscopy. To provide evidence that the observed centres are truly generated in the way we describe, we supplied a 98% isotopically enriched  Its high resolution enabled scientists to investigate very small objects like cells or large molecules. The wide area of application and the gradually dropping costs of electron microscopes led to the fact that today most natural science institutes have such a device. In this research paper we report about another application of the electron microscope apart from its imaging technique, that was to our best knowledge not published up to now. We demonstrate here that the implantation of ions is feasible by the simple means of a scanning electron microscope (SEM) only. Usually an ion accelerator is needed for a precise implantation of atoms, which is not available in many research facilities because of the technical complexity and correspondingly high costs.The development of the electron microscope in the 1930s was a milestone in many fields of natural sciences2. If not explicitly stated otherwise by writing NV centre we refer to the negatively charged type (NV−). The NV centre consists of a substitutional nitrogen atom next to a vacancy in the diamond lattice. The centre has a zero phonon optical transition at a wavelength of 638 nm3 between its triplet ground state 3A2 and its first excited state 3E, which is also a spin triplet. In addition, there is an other decay path comprising a metastable singlet state. The ground state triplet has a splitting at zero magnetic field of 2.87 GHz4 between the mS = 0 and mS = ±1 electron spin sublevels. This energy level constitution opens the possibility for the initialization, manipulation and read out of the centres quantum state and therefore its employment as a qubit7. The method described here is highly relevant for the research work on NV centres because nitrogen implantation into ultrapure diamond8 is a often used technique for the generation of NV centres.The proof of principle of our concept is done with nitrogen atoms/molecules and their conversion and detection as nitrogen vacancy (NV) centres15N) can be directed into the chamber. After the diamond was annealed in vacuum to form NV centres, fluorescence images and spectra of the sample were recorded. Fig. − is clearly visible at 638 nm. Additionally, the ZPL of the neutrally charged NV centre (NV0) can be seen at 575 nm. Both are accompanied by their characteristic phonon side bands. These spectra could be recorded everywhere in the irradiated area, proving that the generated defects are really NV centres. No NV centres could be found in the other sectors of the sample. But a lower fluorescence signal could be measured around the irradiated area, quickly dropping down to the point where individual centres were resolvable. A possible explanation for this effect is discussed below. Figure 9 and taken spectra verified that the fluorescing spots were indeed single NV centres.To demonstrate our method a rectangular area on the front side of an electronic grade diamond (14N or 15N. Their distinction is possible because of the different nuclear spin of 14N (I = 1) and 15N (I = 1/2) that leads to a differing hyperfine coupling to the electron spin (S = 1) of the NV centre. To make a statistically sound statement, the ODMR spectra of 49 centres were recorded in a batch measurement. Figure mS = 0 and mS = ±1 electron spin sublevels. In Fig. I = 1/2 and the electron spin of S = 1 of the NV centre at zero magnetic field. This hyperfine interaction leads to a twofold splitting of the electron spin sublevels and hence the dual separation of the dip in the fluorescence. The magnitude of this hyperfine splitting is determined by a fit of a Lorentzian function to the data that yields a separation of 3 MHz.The generated NV centres were also investigated with optically detected magnetic resonance (ODMR) measurements to identify whether their constituting nitrogen atoms are of the isotope type 5N I = 1/ that lea10 for the hyperfine splitting in the ground state of a NV centre that comprises a 15N atom. In the case of the constituting nitrogen atom of the NV centre is a 14N isotope, a threefold splitting of the electron spin sublevels and hence in the dip in the fluorescence would be expected. The magnitude of this splitting is stated in the literature as −2.16 MHz11. Additional splittings due to the hyperfine interaction of the NV electron spin with other nuclear spins are possible and were indeed observed in some of the recorded spectra. Because only a nuclear spin of I ≠ 0 gives rise to hyperfine interactions, the most common nuclei for this interaction are 13C isotopes. For a profound treatment of this matter we refer to the corresponding literature12. Figure 15NV centre grouped by the magnitude of their splitting. All these centres have a twofold splitting of the 2.87 GHz resonance that ranges from 2.85 MHz to 3.95 MHz.This value is in good agreement with data from the literatureμm, which is fairly close to the intended value of 10 μm. While the lines exhibited a moderate density of NV centres, the circles only featured a very low density of NV centres. In fact only the signal of one set of circles that consisted of a 10 μm, a 5 μm and a 3 μm circle could be located with the confocal microscope. The signal was so weak that it was hardly distinguishable from the background.Following the analysis of the electron irradiation process on the front side of the sample, an electrically insulating PMMA mask comprising a set of lines and circles was created on the surface of the back side by electron beam lithography. The sector of the diamond containing the openings was subsequently irradiated with the electron beam of a SEM with no gas inlet. After the annealing process, confocal investigations of this sector showed an increased signal at the spots were the openings of the mask have been. Again recorded spectra confirmed that the detected fluorescence originated from NV centres. Figure 15N molecules which are led into the chamber and therefore to the sample by the gas inlet  interact with the electrons of the SEM beam by impact ionization yielding nitrogen ions. The positively charged ions then get attracted by the negative potential in the sample. On the acceleration track they obtain a kinetic energy corresponding to the accelerating voltage. With the obtained energy, the ions are now able to penetrate into the sample and interact with the atoms of the sample material e.g. generating vacancies like in conventional ion implantation. While some of the molecular ions are already dissociated by the impact ionization process, the rest of them breaks apart during the collision with the sample surface. In a subsequent annealing process the vacancies become mobile and thereby enabling NV centre formation13.The mechanism for ion implantation via a scanning electron microscope is depicted in Fig. 15N isotope. No spectra could be assigned to NV centres comprising a 14N isotope. That corresponds to a ratio of at least 55.1% of 15N containing centres. Considering the natural abundance of the 15N isotope of 0.364%14, nitrogen atoms that got into the sample during the manufacturing process or their incorporation during other steps of the experiment by accident can be ruled out as the source of the 15NV centres. The conducted experiments prove that the generated NV centres are truly formed from the implanted 15N ions and therefore that our concept is correct.Even so the method was demonstrated by the implantation of nitrogen ions into diamond, it is expected that because of the underlying physical processes  it will work for any other ion species in the gaseous state and also for other insulating substrates. Since the kinetic energy of the ions is limited by the accelerating voltage of the electron gun of the SEM, energies from less than 1 keV up to 30 keV should be feasible. In 27 of our 49 recorded ODMR spectra the observed hyperfine splitting could be clearly assigned to NV centres which are constituted of a 15. Furthermore, a spectral broadening was observed for some centres that is probably induced by paramagnetic impurities which are located at the surface as well16. The remaining 22 centres that could not be assigned probably either had such a disturbing environment that their spectra were too much deformed to reliably assign them to 15NV or 14NV centres or the tracker simply failed to keep track of them. Nevertheless, the majority of the centres exhibit fluorescence and ODMR spectra that are comparable to those of NV centres created by classical ion implantation17.We attribute the deviation of the magnitude of the splitting of some centres from the literature value to the particular surface proximity of the NV centres, that arises from the low implantation energy of the nitrogen ions (≤700 eV). Because near the surface the centres are exposed to strain which influences the magnitude of the splittingThe observation that a lower density of NV centres was also generated around the area which was irradiated with electrons can be explained by the presented implantation mechanism as well. Because the delivered nitrogen molecules distribute equally in the chamber of the SEM and will have different directions of movement, the vector of motion of some of the nitrogen particles will confine a smaller angle with the sample surface then others. If the angle is small enough the deflection of the particle, that is induced by the electron generated potential in the sample, will not suffice to direct it on a trajectory where it hits the sample in the irradiated area. The ion will instead collide with the surface only when it has already passed the irradiated area, so that it is implanted a bit away from it.15N isotopes in the centres, that the way the N atoms got into the sample material is as we described it. We also showed that the location of the implanted ions can be restricted to small areas by using an electrically insulating PMMA mask.In conclusion, we have introduced a new method for the implantation of ions into electrically insulating material. This method is based on the impact ionization of gaseous particles, which are brought into interaction with an electron beam and subsequently attracted by a potential induced by the same electron beam, which eventually leads to the implantation of the ions into the insulating sample. It stands out from other established implantation techniques because of its technical simplicity and the associated low costs. The proof of principle was done with nitrogen atoms/molecules that could be verified through generated nitrogen vacancy centres. While fluorescence spectra show that the created colour centres are indeed NV centres, the recorded ODMR spectra prove by identification of the μm × 516.4 μm large area on the front side of the sample was irradiated with a low energy electron beam (Ekin = 700 eV) with a beam current of 35 pA for about 100 hous in a SEM (DSM 982 GEMINI Zeiss), which was modified with an additional gas inlet. The gas inflow, which comes from a metallic cylinder filled with isotopically enriched nitrogen  is precisely controlled with a needle valve. The gas is then guided via a silicone tube to a copper ring that is placed between the beam exit and the sample. Six small holes were drilled on the lower part of the inner face of the ring to direct the gas onto the sample. The pressure in the chamber was regulated to 6⋅10−6 mbar. After the implantation process the sample was annealed in vacuum at 800 °C for 2 hours to trigger the NV centre formation and subsequently cleaned by etching in a mixture of nitric acid, sulfuric acid and perchloric acid at boiling point for 4 hours. Fluorescence images and spectra of single NV centres and NV ensembles were recorded with a home build confocal microscope equipped with single-photon counting modules and a CCD supported grating spectrometer using a 0.95 NA air objective and a laser light wavelength of 532 nm. Additionally, spectra of ODMR measurements of the ground state of single centres were recorded with another setup that uses the same laser light wavelength and a 1.35 NA oil objective. ODMR is based on a decrease in the emitted fluorescence intensity of the centre caused by the depopulation of the mS = 0 state that is achieved by scanning microwaves in an appropriate frequency range. The ODMR data were recorded without applying a magnetic field (B = 0) and includes continuous wave spectra  as well as pulsed spectra .An electronic grade, single crystal diamond, grown by chemical vapor deposition, was used as a sample in this experiment. The manufacturer, Element 6, stated the initial nitrogen content as below 5 ppb. In a first step the diamond was cleaned in an ultrasonic bath of acetone followed by isopropyl alcohol. Then a 661 μm) and circles (diameter of 10 μm to 0.5 μm) was drawn by exposing the sample to a beam of focused electrons at the dual beam microscope Nova NanoLab 200 from FEI and subsequent developing. This procedure formed an electrically insulating mask consisting of PMMA on the sample surface. Afterwards, in the sector of the diamond comprising the set of structures, a 400 μm × 300 μm large area was irradiated with the electron beam  of a SEM (CS44 CamScan) with no gas inlet for 96 hours. The chamber pressure was 5•10−6 mbar. After the irradiation process the mask was removed in an ultrasonic bath of acetone. The following annealing and etching processes were under the same conditions as before and the subsequently recorded fluorescence images and spectra were taken with the aforementioned confocal microscope.After the evaluation of the first electron irradiation process with the optical setup, the sample was once again cleaned in an ultrasonic bath of acetone followed by isopropyl alcohol. Then the back side of the sample was spin coated with a PMMA electron beam resist at 3500 rpm for 30 s and another 30 s at 3500 rpm down to 0 rpm. Following this a set of lines (width of 10


Effectiveness of postural control techniques to compensate for oropharyngeal dysphagia have been recommended and used by several clinicians. However, the inter‐rater reliability of these techniques is not well understood. The purpose of this study was to clarify the ambiguity of postural control techniques using statistical analyses. A total of 50 clinicians involved in dysphagia treatment participated in this study, where a healthy male served as the simulated patient. The following clinically used postures were measured by two investigators on two separate days: chin down, right/left incline, and right/left rotation. Postural angles were measured twice by two investigators on each day. Data obtained for the angle of each posture were visually displayed. Data from both investigators were assessed for each posture using the Youden plot, which analyzes data variability for systematic errors and accidental errors separately. The correlation coefficient for examining the measurement error between investigators was calculated. The results showed considerable variation between clinicians regarding the postures used, and significant differences were noted each day. The correlation coefficient for a total of four measurements was more often lower on Day 2 than that on Day 1. The details of the instructions provided by clinicians were not fixed, and the same specified posture was not reproduced even when instructions were provided to the same subject. These findings suggest poor inter‐rater reliability because of the variability of selected postures when using statistical analyses. Therefore, standardized postures need to be developed that can be easily measured and reproduced. Compensatory techniques are designed to make swallowing safer and more efficient  remain ambiguous. The purpose of this study was to provide objective data about inter‐rater reliability of postural control techniques practiced by clinicians familiar with postural controls using statistical analyses.22.1This study was approved by the Ethics Committee of Showa University School of Dentistry .Before the initiation of the study, written informed consent was obtained from all participants. A total of 50 clinicians (48 dentists and two speech‐language therapists) involved in dysphagia rehabilitation participated in this study. The years of the experiences were 1 through 17. It was verified that each clinician used postural control techniques in their practice.A healthy male volunteer  served as the simulated patient, and it was confirmed that he had no history of orthopedic disease, abnormalities of cervical alignment, or abnormal findings such as muscular spasms, which may affect adjustment of the instructed posture. The simulated patient wore the same clothes throughout each measurement. Additionally, he wore a swimming cap to reduce systematic error due to hair and a singlet to allow easy assessment to the upper body and cervical region.After the simulated patient was placed in the targeted posture, the range of motion angles was independently measured by two investigators .2.2The University of Tokyo‐style angle gauge  was used for measurement Figure  Each invLateral incline (right/left bending) of the upper body was measured in terms of the targeted vertical line at the midpoint of the Jacoby line (the line connecting the highest point of the iliac crest on both sides). The rotation axis of lateral incline of the upper body was a sagittal line passing through the center of the fifth lumbar spinous process. The angle between the target line at upright sitting position and target line at the adjusted posture was measured and evaluated as the angle of lateral incline posture Figure b.Cervical rotation (right/left bending) was measured by drawing a vertical line passing through the midpoint of the line connecting the acromion on both sides. This line is equal to a line passing through the occipital apex and nasal apex. Rotation axis of the cervical rotation was considered as a vertical line from the floor passing through the midpoint of a line connecting the acromion on both sides. The angle between the targeted line at the start of the upright sitting position and that at the adjusted posture was measured and evaluated as the angle of cervical rotation posture Figure c.2.3Each clinician applied the postural control techniques displayed on the monitor to the simulated patient. Only the name of each posture was displayed on the monitor: chin down, right and left incline of the upper body, and right and left cervical rotation. Each clinician placed the simulated patient in the position they saw on the monitor. Once they were satisfied that the posture was correct, they raised their hand, and the investigators came into the room to take measurements of the posture  and accidental errors . The size of the ellipse indicates magnitude of bias. If there is no correlation between the two sets of data, bias is represented by a circular distribution expressed with broken lines. Using this model, a large amount of bias is consistent with poor reproducibility of the instructions provided by the clinicians, while limited bias shows the converse. In this manner, the effectiveness of the required instructions provided by an instructor can be assessed based on their reproducibility Figure . Additio4p = .69, Table The results for the angle of the chin‐down posture are shown in Figure p = .57, Table The results for the angle of the right incline of the upper body posture are shown in Figure p = .78, Table The results for the angle of the left incline of upper body posture are shown in Figure p = .58, Table The results for the right cervical rotation posture are shown in Figure p = .71, Table The results for the left cervical rotation posture are shown in Figure On the Youden plot, the 95% confidence interval was elliptical, and systematic error was noted for all measurements plotted. This result represents poor reproducibility because of the variability of selected postures. Nevertheless, no significant difference was noted between the angle of each posture on Days 1 and 2.5The settings for patients with dysphagia include hospitals Cherney, , nursingThe effectiveness of postural control techniques is stated in the “Summary of Training Methods”  measurements were taken, where there is a need to examine three‐dimensional changes including the trunk of the body  as a large number of patients with dysphagia consume their meals while being seated on a chair. In this case, the posture is affected in three dimensions. This was a pilot study to determine the inter‐rater reliability of postural control techniques using statistical analyses, and we used only one simulated patient. Further study involving patients with different physiques, physical characteristics, and age is required.A limitation of this study was that only two‐dimensional (None of the authors has any conflicts of interest to declare with respect to this study.


In this work we study the assisted translocation of a polymer across a membrane nanopore, inside which a molecular motor exerts a force fuelled by the hydrolysis of ATP molecules. In our model the motor switches to its active state for a fixed amount of time, while it waits for an ATP molecule which triggers the motor, during an exponentially distributed time lapse. The polymer is modelled as a beads-springs chain with both excluded volume and bending contributions, and moves in a stochastic three dimensional environment modelled with a Langevin dynamics at a fixed temperature. The resulting dynamics shows a Michaelis-Menten translocation velocity that depends on the chain flexibility. The scaling behavior of the mean translocation time with the polymer length for different bending values is also investigated. Cell drug delivery, DNA, RNA and protein passage through cell membranes and nuclear pores, and DNA injection and packaging by phage viruses are only some interesting examples of a broad biological phenomenology4. An important related application is the use of nanopores to unzip and translocate single DNA chains with the purpose of performing fast and detailed DNA sequencing9.The passage of polymers thorough nanopores is also a fundamental problem in chemical and industrial processes. In this context, many efforts are made in nanotechnological applications, that try to emulate the complex biological processes involved in the translocation problem10. In some very simplified models a single barrier potential, eventually depending on time, is introduced to depict the overall translocation process14; in others, stochastic and ratchet-like forces and potentials are used refs In spite of the many studies present in the literature, the understanding of polymer translocation at the nanoscale still deserve deeper investigation. In fact, the number of parameters involved in the models and the presence of nonlinearities together with the underlying stochastic environment in which nanoscale objects move, make this study complex theoretically and hard computationally, even nowadays. DNA chains are paradigmatic examples of this difficulty. With the ambition of efficiently describing the biological matter in a reasonable time, different mesoscopic models for polymer translocation have been introduced20, most studies of translocation have been performed, so far, mainly under constant forces. These forces, are generally associated to potential and concentration gradients observed between both sides of the membrane. The role of active nanopores, with mechanisms to assist the polymer translocation, has been only more recently considered. The simplest active nanopore corresponds to the opening or closing of the channel due to either the presence of electrochemical membrane forces21 or random bonding of ligands22. It has been usually modelled by a dichotomous Markov noise 25 which drives the molecule. In other cases, the flickering activity of the pore channel is modelled as a sinusoidal pore actuation28. In both cases a new time scale, associated to the pore activity, appears in the description of the phenomena.Motivated by the passive pores studied in different experimentsϕ-29. This motor is able to inject out (or pack inside) its DNA by exerting a force supplied by the hydrolysis of ATP molecules which bind to the motor sites and activate its movement30. The force exerted by the nanomotor can be modelled by a specific stochastic dichotomous force, that we call dichotomous ATP-based motor noise force. This force has been successfully introduced to study translocation restricted to a one dimensional dynamics32.A landmark example of active translocation in the biological realm is the translocation assisted by molecular motors. Recent well known experiments have risen a considerable attention to the specific and very interesting driving features of the molecular motor of the virus bacteriophage In addition to its biological interest, understanding and controlling bistable forces has an undoubted interest in the manipulation of objects at the nanoscale. In fact, molecular motors represent a highly effective way to exert a force at the nanoscale worth to be mimicked in the artificial realm. So, a properly prepared system can be driven in a controlled way by changing the concentration of the fuel molecules in the solution, which directly modifies the motor activation rate, and thus the exerted force.33 and its modifications. There, polymers are constituted by beads connected each other by harmonic springs. Natural improvements of the model take into account polymer bending energy and excluded volume interactions. Indeed, recent studies show that translocation significantly depends not only on the polymer size but also on its flexibility and on the interactions between monomers and pores36.Concerning the polymer modelling, the usual approach is based in the Rouse chainτ of the polymer as a function of the motor activation rate. We will put special attention to the study of the dynamics of the system for different polymer size (number of monomers) and persistence length (flexibility or bending). This latter is an important parameter of the system whose influence has been rarely studied so far in translocation context.Aimed by all these results, this manuscript proposes the study of the translocation of a linear polymer molecule in the 3d domain driven by a specific ATP-fuelled biological force acting inside the nanopore. We will specially focus on the study of the mean translocation velocity and translocation time (TT) N identical monomers moving in the three-dimensional space. We use a modified Rouse model33 which includes bending energy, excluded volume effects and interaction with the membrane and the pore. The elastic potential energy is given byke is the elastic parameter, ri is the position of the i-th particle, i and i + 1, and d0 is the equilibrium distance between adjacent monomers.Our polymer model is based in a chain formed by kb is the bending elastic constant, θi is the angle between the links di+1 and di, and θ0 the equilibrium angle, with θ0 = 0 in our case. With this term, our model is a discrete version of the worm-like chain (WLC) model.The model takes into account the bending energy of the chain with a term given byrij is the distance between monomer i and monomer j.In order to consider excluded volume effects between the monomers, a repulsive only Lennard-Jones potential has been taken into account:ξi(t) stands for the Gaussian uncorrelated thermal fluctuation and follows the usual statistical properties α = x, y, z. The operator used above is defined as: The dynamics of every monomer of the chain is obtained by the overdamped equation of motionFsp includes both the chain-membrane and chain-pore spatial constraint. This interaction force is modelled with the same repulsive Lennard-Jones potential described in Eq. . Fc is the constant force used in the study of passive pores . η(t) is associated to the molecular motor pulling the polymer. It fluctuates between 0 and FM. For η(t) we use a modification of the usual dichotomous noise31. Activated by ATP absorption, η acts during a fixed time TM, along this time η(t) = FM. After this time, the motor relax and η(t) = 0 until a new ATP molecule is absorbed. This happens with a probability Pt′ = 1 − et′/T−, being t′ the time spent by the motor in its inactive state, and T its mean waiting time  during a fixed time TM = 1/ν0. After that time the motor returns to its rest state. A new force will be applied when the next ATP suitable quantity is absorbed and hydrolysed, which happens after a mean time T = 1/ν, which follows an exponential distribution of waiting times according to the underlying Poisson process. The timing in the kinetics can be summarised as follows: For activation rates ν < ν0, the motor remains at rest for an average time longer than TM, while the opposite occurs  if ν > ν0.The energy used by the motor to provide the driving is given by the ATP hydrolysis. The simplest way to model this phenomenon, is to consider that each ATP hydrolysis activates the motor for a fixed working time 37. With the above definitions, the Michaelis-Menten (MM) law for the transfer velocity arises naturally from the model. In fact, the fraction of active time with respect to the total time is given byν is proportional to the ATP concentration , and k2 gives the probability to form the product P per unit of time. In our mechanical and individual case (single motor and single ATP hydrolisation event) Z represents the ATP-motor binding, which occurs with the rate ν (i.e. ~k1[ATP]), while the product of the reaction P represents the motor action which is completed within a time TM = 1/ν0 (ν0 ~ k2). These relationships are in agreement with the definition of the Michaelis constant kM = k2/k1. For a more complete analysis of the MM law the reader can also refer to refs The relationship between the mechanical active-rest kinetics of the motor and the MM law goes beyond the statistical ansatz x-axis) is calculated by summing up the N monomer terms of equation , and shows the Michaelis-Menten dependence. The last term Fw comes from the interaction of the polymer with the membrane. In fact, while all the internal force terms in equation  dependence follows the MM behaviour, dominated by the motor contribution to the total force. Note also that the polymer velocity goes to zero as 1/N for large chains as expected when a motor acts on a small number of monomers nM of a polymer which moves in a dissipative media.We identify here three contributions to the total velocity. The first term accounts for the driving of the constant external force, which acts only on the monomers into the motor. The second term is related with the molecular motor kinetics, explained above. It is given by the force felt by the equation  sum up tτ, the mean value of the TT of the chain for different parameters of the model and different polymer lengths.We are interested in characterising the translocation process of the polymer through the pore. We will present below the results for LM = 5d0, longer than the distance of two consecutive monomers. We calculate the translocation time as follows: All the simulations start with five monomers at the right end of the polymer lying inside the pore and the others linearly ordered and sited at the equilibrium distance. During a thermalisation time tt = 1000 t.u. the chain evolves under the action of thermal fluctuations while keeping fixed the position of the five monomers inside the pore. After that transient time, the restriction over the first five monomers is removed, and the evolution of the chain under the dynamics given by Eq.  of the event. Later we will average over many translocation processes to get the values of τ.It is usual in literature that a channel with either zero or short length is used to study the polymer translocation. In order to approach a more realistic picture, in our works we use a channel with a fixed length, n by Eq.  is monitvCM as the ensemble average  of the ratio between the displacement of the CM of the chain and the corresponding employed time . It is worth to remember that the relation between translocation velocity vCM and mean time τ is not immediate since in general, At the same translocation conditions, we define the center of mass (CM) velocity of the polymer The given definitions are suitable to compare TT of chains with different lengths because the border effects result minimised since five monomers are always inside the pore during the simulation time in all the cases studied.m, l0, and kBT = 4.1 pNnm) and the simplest model with kb = 0. We have fixed our simulation temperature to kBT = 0.1 in dimensionless units. This choice fixes our energy unit in l0 = 1.875 nm and m = 936 amu25, we obtain 41.Following ref. tion Eq.  is \docuLH = 2, LM = 5. The rest distance between adjacent monomers is d0 = 1 and ke = 1600, large enough to maintain the bonds of the chain rigid enough. The Lennard-Jones energy is σ = 0.8. The values of d0, σ, LM and LH guarantees that the polymer is maintained almost linear and ordered inside the pore. Also, the different choices of the bending constant kb, gives the possibility to study the TT for different persistence lengths of the chain, which basically gives the stiffness of the polymer (i.e. its resistance to bend). For our model Lp = kb/kBT. Thus for example we obtain Lp = 5 (in units of d0) for kb = 0.5. Regarding the actuating forces we set Fc = 0.1 and FM = 0.2 along our work.The dimensionless geometrical values used in the simulations are Ng has been simulated. From them a number of Nexp = 2000 successful translocations have been reached and both the mean translocation time τ and the mean velocity vCM have been then computed. From these values, we also compute the translocation probability Pin as the ratio Nexp/Ng. To finish we have to mention that since we deal with time dependent pulling forces inside the pore, we have also averaged on the initial value of the driving by randomising the initial phase of the force, that is considered as a random variable with a uniform distribution over its possible values.For every set of parameters, a number of numerical experiments vCM of a polymer with N = 32 monomers at different values of the bending parameter . We observe that the polymer velocity follows Eq. . Thus, the main contribution with kb comes from the Fw term, as far as this model can devise. A different approach has been followed by Adhikari and Bhattacharya42.The force sing Eq. . This foτ of the system as a function of the motor activation rate ν calculated for N = 32. τ decreases monotonously as ν increases and reaches a limit value for large enough values of ν, when the waiting time goes to zero and the motor stays active most of the time. The results are presented for four different bending values and the curves are normalised with respect the high rate value τHR in each case.Figure N = 16, 32, 64, 96 and 128. In all cases we find that τ increases with kb. In addition, the translocation probability Pin is almost 1 for all rates at high kb, i.e. almost all the simulated events translocate; but Pin is lower than 1 in a wide moderate-to-low activation rate region, reaching the value Pin = 0.6 for kb = 0. Note that the backward force required to prevent the polymer to translocate has to be stronger for rigid chains than for low kb values, since the escape from the pore needs a larger displacement of the center of mass of the system to leave the motor, and so, a higher work is required to pull more rigid chains.Similar behaviour is observed at other studied lengths, namely vCM and τ, it is observed that kb . For each of the four kb values we can notice a narrower distribution at higher rates (ν = 102) with a lower mean TT value, with respect to a wider distribution at lower rates (ν = 10−2) having a higher mean TT value. All the distributions are almost symmetrical, and this feature can explain the almost linear relationship reported in Fig. Figure α is the scaling exponent for the gyration radius of the polymer, n = nM + 1 and b the only free parameter of the proposed fitting function. We will see that in spite of its simplicity the proposed equation gives account of the observed scaling behaviour of the system in a wide range of rate values.An interesting issue in this study concerns the scaling properties of the translocation time of the polymer with its size. Below we will propose and check against our numerical results a very simple relationnM is the number of monomers remaining inside the pore, and d0 is the inter-monomer distance. Assuming that n = 1 + nM = 6. For large polymers, the scaling follows the law To depict a simple intuitive model, let us first consider the polymer translocating in a straight line. The translocation length is then ∝1/N Eq.  we get \see ref. . The aboThe three-dimensional stochastic movement of the polymer outside the channel gives rise to a general reduction of the translocation time, which depends on the polymer and environment properties .Rg we can roughly assume In our simple approach, we can assume that the translocation length changes because of the conformational shape adopted by the polymer at both sides of the pore. Since the size of the polymer is given by its gyration radius 44νF the so-called Flory coefficient. For a more refined derivation of this case see also ref. νF = 0.5 for an ideal chain in 3D (without interaction between no consecutive monomers), νF = 1 for a rod (rigid chain)50.For large polymer this expression becomes kb, being kb = 0 and tending to α = 1 as we increase kb. Regarding its variation with the rate ν, a weak dependence is observed, with α decreasing when the rate increases. Values are given inside the related figure.We have computed (see Appendix) the gyration radius of our system at different bending values and frequencies. We observe it increases with α obtained from the Rg analysis, against our numerical observation for τ. We observe excellent agreement in all the cases, in spite of the different approximations employed in the derivation and the moderate to small size of the chains studied.In Fig. τ(ν) curves for different values of N at three bending values, kb = 0.0, 0.5 and 2.5. Here we use the same scaling exponent α for all the rates (we choose the high rate result). As expected, the scaling is excellent at high ν, while the data dispersion at lower rates indicates that the exponent α depends also on the value of the rate, as explained above. It is worth to note, see the insets, that the translocation probability does not change with N, being mostly a function of the bending parameter.Figure Lp = kb/kBT. Here we use a discrete version, so deviations from the continuous model may be found for small N values. In order to study the translocation behavior of the polymer at different values of Lp we have performed simulations for different values of the bending from kb = 0 (freely-jointed chain model) to high kb values (extensible rigid chain). The results have been already presented and commented in previous figures and sections of this article.Persistence length is the basic parameter measuring the stiffness of a polymer. For the continuous WLC model the persistence length is given by τ and the center of mass velocity vCM as a function of Lp. We show the results for the N = 32 polymer and at low, medium and high activation rates . We also show the constant force result corresponding to the ν→∞ limit. As expected, a saturating behaviour of τ for increasing values of Lp is observed. The inset shows a similar saturating behaviour for the velocity. The curves for ν = ∞ and ν = 102 completely overlap as at this latter value the motor is almost continuously actuating.In Fig. τ and vCM depends on ν, kb and N. However, given the definition of Lp = kb/kBT, it is possible to define a new parameter N/Lp giving account of the number of effective segments of the system. The question now is if it is possible to write either τ or vCM as a function of ν and N/Lp, thus reducing the number of parameters of the system from 3 to 2. We have investigate this issue and the answer is negative. For a given activation rate, it is observed that simulations data at different values of N and kb do not collapse to a single curve when plotted as a function of N/Lp.We have seen that the observables of the system, We have studied the translocation of a polymer chain through a repulsive, uniform pore membrane in a thermal fluctuating environment. The polymer is pulled by a time dependent force modelled as a dichotomous stochastic motor fuelled by the hydrolysis of ATP molecules which bind to the motor at a Poisson rate and activates a mechanical work during a fixed time lapse.Nα1+, with α weakly dependent on the activation rate of the motor.The objectives of our work are to study the specificity of the pull force used inside the pore, and to investigate the translocation time dependence on the flexibility and length of the polymer chain. We propose a scaling behaviour of the translocation times with the polymer length according to a power law of the type 31 to a more realistic and biologically interesting system, accounting for motion in the 3-D domain, polymer-membrane interactions, and ATP based driving motor. Dynamics has been studied for different motor actuation rates, polymer sizes, and rigidities.This work is the natural extension of our previous studiesi.e. a MM dependence with the activation rate of the motor, which directly depends on the ATP molecule concentration in the surroundings of the machine. The MM velocity for an ATP-driven machine has been extensively measured in many experiments with different types of motors. Examples are the transport velocity of a stepping motor like kinesins52 (with or without load forces) as well as the packaging velocity of the DNA of the bacteriophage pulled inside the virus capside by its motor complex37.The nature of the ATP-based pulling gives rise to monotonic translocation time as a function of the activation rate of the motor. The mean velocity of the polymer is found to have a specific and very clear behaviour, average working time of each molecular motors using ATP in these conditions, results in a MM kinetics.We show here that such MM-like behaviour arises in a natural way in the introduced model. Specifically, the translocation velocity depends on the motor activity which drives the polymer for a certain fixed time, and stays inactive during a certain Poisson distributed waiting time. The Beyond its biological interest, the study of polymer translocation through active nanopores reveals its importance in understanding the translocation aspects of long molecules assisted by motors at small scales, and represents a starting point for the construction from scratch of nanotechnological objects. In this regard, without any purpose to reproduce in detail some specific experiment, this work is an attempt to model the dynamics at the nanoscale with a very comfortable approach under the realistic constraints imposed by the ATP energy supply of a typical molecular motor. Further improvement of this kind of description can be devoted to a more accurate modelling of the pore channel in both: the structure of the very pore together with its interaction with the passing through molecule, and a more complex characterisation of the polymer by enlarging its internal degrees of freedom such as the diversification of the monomers properties according to the different molecular components of a real chain.α introduced in our scaling analysis of the polymer translocation time. This is based in the computation of a dynamical gyration radius as follows: given a polymer with N monomers we define Ntrans as the number of monomers in the trans side of the system . At this time we compute the instantaneous gyration radius of the system, and average it over Nexp translocation realisation:Rg = a(Ntrans − 1)α.This appendix is devoted to provide details on the numerical calculation of the exponent N = 32 beads polymer and at different values of ν and kb. Fitting is always good and the exponents (given in the figure), decrease a bit increasing the rate, but depends more strongly on the stiffness of the system, kb. As expected the gyration radius  increases with kb. The obtained exponents were used in the scaling study of the polymer translocation time as discussed in Section 6.Figure dynamical gyration radius. Evidently, the calculation of any magnitude along the translocation process, constitute an out of equilibrium measure, though the slower is the translocation dynamics, the better is the approximation to a thermodynamic equilibrium . In this sense is not surprising that the gyration radius is a function of both the activation rate of the motor (and so of the translocation velocity), and, of course, strongly dependent of the stiffness of the chain. That is why we can observe in Fig. We have to mention that differently from the usual definition of the gyration radius, which makes sense in thermodynamic equilibrium conditions, here we calculate a somehow


The purpose of this investigation is to measure, characterize and report stray photon leakage and scatter radiation measurements from the Mobetron, an intra‐operative electron linear accelerator designed for use in an operating room environment. The study is needed due to recent changes to the shielding design of the Mobetron, and also to provide specific information that may be required by regulation in various jurisdictions. An analysis is performed on a number of manufactured units to determine an average 3D stray photon radiation map. This information provides a basis for determining patient‐based load restrictions and/or additional shielding for the operating room. The data presented evaluates the number of procedures for which the Mobetron may be safely operated in a typical unshielded operating room.PACS number: 87.53.‐j; 87.56.‐v An assessment of stray photon radiation and patient load has been previously published, but recent improvements to the Mobetron shielding design coupled with more detailed measurements on contemporary units make this update desirable.The purpose of intra‐operative radiotherapy (IORT) is to deliver a single fraction dose of up to 20 Gy to an exposed treatment volume in an operating room while the patient is under anesthesia. The beams may be collimated using applicators with or without bevels. Portions of the field may be blocked using lead, sensitive structures may be relocated or shielded, and bolus may be used to increase the surface dose if needed. The relatively low leakage radiation of the IntraOp Mobetron allows the unit to be used for radiation therapy delivery in an unshielded operating room.1 An aThis study will allow users to establish appropriate workloads for unshielded operating room(s) and select the best operating room(s) to conduct IORT in an unshielded environment.(2.3g/cm3) were stacked to simulate various thicknesses of the operating room floor  in concrete of the radiation from the Mobetron . Concrete blocks (40 cm by 20 cm by 10 cm) of standard density Dosimeters were positioned under the set of concrete blocks. Measurements were taken at 100 and 150 cm from the beam axis for all energies. Blocks were wide enough to ensure that no leakage radiation from the sides would reach the detectors.10 Gy/min for all nominal electron energies: 4, 6, 9, and 12 MeV. Delivered dose is defined as measured with the 10 cm circular applicator in a water phantom at Dmax for the beam energy in use. The Mobetron head was positioned with the beam pointed vertically downwards and moved to the maximum vertical limit of travel. Thus the worst case scenario was implemented with the maximal part of the beam missing the beam stopper.During leakage data acquisition, the Mobetron was operated at the calibrated dose rate of A standard quality assurance fixture was attached to the end of the collimator. The fixture consists of the 10 cm cylindrical aluminum applicator, with 0° bevel, and an attached plastic phantom 13.5 cm in diameter and 8.5 cm long. Five detectors (see detector details below) mounted on a vertical pole at 0, 50, 100, 150 and 200 cm above the floor were used for the measurements .Hp(10) and Hp(0.07) dose equivalents to the accuracy of 1 μSv. The Hp(10) is the dose equivalent at 10 mm depth in the body at the point of application of the detector. Correspondingly, Hp(0.07) is the dose equivalent at 0.07 mm depth and usually used as estimated value for the skin dose.To measure and control the contribution of low penetrating radiation (electrons and low energy X‐rays) to the measured dose, solid state detectors MGP DMC2000XB  were chosen. Detectors were calibrated by an independent lab within a year of an experiment. These detectors are capable of separately measuring both uivalents3 to tBlocks of gypsum (6 cm thick) were placed in front of each detector for all measurements to attenuate the scattered low penetrating radiation and report only the magnitude of the estimated absorbed dose due to photon radiation (see discussion below).A Mobetron‐based coordinate system (CS) has an origin of  at the point on the floor under the center of the beam stopper Fig. . Such a Exposure data were measured and analyzed at multiple points around the Mobetron. Experimental data were averaged over four treatment units and then fit using the Fourier series. Estimated relative standard deviation of the presented data is 15%.X=0,Y=0 and Z=100. These planes are the same as reported in the original Mobetron leakage paper by Daves and Mills, and one meter above the floor is a typical height at which the surrounding room leakage surveys are performed.The radiation exposure is reported in the three orthogonal planes in CS: nd Mills,2 and Measurement results for each of the planes are presented for a 300 cm radius circle, as measured from  every 22.5°. When a 300 cm distance was unachievable , the data were measured as far as possible from the center of the circle and the inverse square law was used to generate the data at 300 cm.To accelerate electrons, the Mobetron uses two X‐band 9.3 GHz collinear accelerators. The first is supplied with constant power and accelerates electrons to 4 MeV. The second is supplied with variable RF power and produces electrons from 4 MeV to 12 MeV at the output. The accelerators are encased in a lead and steel “strong‐back”, significantly reducing the normal guide leakage. In order to deliver the same output dose, the Mobetron gun current is decreased by almost a factor of 10 between 4 MeV and 12 MeV. The intensity of the top radiation source is correlated with the gun current and decreases by a factor 10 with an increase in energy, while bottom source increases its intensity according to the well‐known fact that bremsstrahlung in electron beams rises rapidly with energy.It was determined that the source of radiation is distributed along the internal beam path. Two significant regions can be mentioned: the top one between the first and second guide sections, and the bottom one somewhere down the beam line.4 The Hp(10) and Hp(0.07) measured by uncovered detectors differed by factor of 10 at some measurement points. It was found experimentally by comparing Hp(10) and Hp(0.07) that for current Mobetron construction, 6 cm of gypsum board eliminates the effect of LPR completely, while 4 cm of gypsumboard shielding produced numbers 10%–40% higher for Hp(0.07) relative to Hp(10).It was found that low penetrating radiation (LPR) contributes significantly to the leakage exposure. Values of the ∼30 cm of concrete was placed over the detectors.The transmission of the concrete was measured for the Mobetron radiation using the setup shown in Fig Effective TVL values measured in this experiment show how thick a concrete floor should be in order to attenuate the radiation exposure under the floor by a factor of 10. No corrections to obliqueness of the beam path or any other corrections were performed. Effective TVL decreases from 41 cm at 100 cm from the beam axis to 28 cm at 150 cm from beam axis.There was no statistically significant difference detected in attenuation factors for the stray radiation generated by 6, 9 or 12 MeV within error of the measurement. This fact can be explained by the two point geometry of the Mobetron source of radiation. The top source provides most of the radiation at low energies (due to high gun current); the bottom source generates more radiation at higher energies. (as shown in its Table B.2), which reports a concrete TVL for a 10 MeV energy beam as 41 cm and for a 6 MeV beam as 37 cm.The 100 cm data agree reasonably well with NCRP 1515  showed that the three highest energies – 6, 9, and 12 MeV –produce similar photon radiation exposure, while 4 MeV consistently generated For all values of Z, except directly on or just above the floor, it can be stated with confidence that 4 MeV produces more stray photon radiation than 12 MeV. This can be explained by the two source structure of the Mobetron leakage described above.z=100). This projection is useful for determining the potential radiation exposure in rooms and areas adjacent to the OR.Figure There is about 20% less exposure to the right (positive X) of the unit. This can be attributed to the presence of the magnetron and pulse transformer, which are mounted to the right side of the guide and serve as additional shielding for the leakage radiation.Otherwise the exposures are quite symmetrical with the expected minimum exposure behind the treatment unit due to its self‐shielding.2.2 μSv/10 Gy at the back of the unit and a maximum of approximately 4.5 μSv/10 Gy in the front of the unit.In the Z‐plane, exposure averaged over energies has a minimum of approximately z=0) is provided in Fig. Radiation exposure of the floor and ceiling differ significantly from the Z‐plane measured at 100 cm above the floor. Exposure diagram showing the distribution of the ambient radiation dose along the floor  is maximal right over the beam stopper and slightly in front of the unit. Maximum leakage in this plane is about 3 μSv/10 Gy. Assuming the ceiling above has same thickness of concrete as floor below; exposure above the ceiling will be less than 1 μSv/10 Gy at the maximum and is negligible for all practical purposes.Ceiling radiation exposure . The height dependence of the exposure is nonsignificant at such distances.Attempts to find a theoretical model which would predict distribution of the radiation at distances closer than 300 cm using either a ‘single point source’, ‘dual point source’ or ‘dual point/linear source’ failed. However, at distances greater than 300 cm, exposure measurements in the Z‐plane can be reasonably described with simple point source model. Measurements at 400, 500 and 700 cm confirmed that beyond 300 cm, leakage radiation from the Mobetron drops as ±45∘ about the y‐axis and a maximum of ±30∘ about the x‐axis. As is shown in Fig. The effect of rotating the Mobetron from its vertical position must be addressed separately. The Mobetron can rotate a maximum of For the floor below, the 45° scatter is of lower energy than the scatter just missing the beam stopper when the Mobetron is in a vertical position (see discussion about effective TVL above). Thus, even though the exposure on the floor when the Mobetron is rotated to 45° is higher than the exposure when the Mobetron is in the vertical position, the attenuation by the floor is greater for this softer energy scatter.For adjacent rooms, when the gantry is rotated to its maximum position of 45°, the stray radiation will be highly directional, as can be seen by looking at the Y‐plane exposure for the scatter not absorbed by the beam stopper Fig. . At a diThese measurements allow the calculation of an allowable workload in cGy/week for all occupied areas surrounding the Mobetron. A worst case scenario for the Mobetron is not clearly defined. As mentioned in the results section, the Z‐plane leakage is maximal for 4 MeV, while floor leakage is maximal for 12 MeV. The decision was made not to include 4 MeV in the calculations since this energy has a very low use factor in practice. Except where mentioned explicitly, all presented data average the exposure rate measurements over 6, 9 and 12 MeV energies, assuming an equal workload contribution and all treatment positions weighted equally.Table Table These tables can be used as guidelines to quickly determine which operating room(s) and which orientation of the Mobetron may be most suited for operation from the perspective of allowable radiation exposure to surrounding areas.For the Mobetron, every OR will have a limit on the maximum number of monitor units or beam‐on minutes that can be delivered. Most of the time, Mobetron usage will be limited by the maximum weekly exposure that is allowed. In rare cases where the patient receives substantial treatments to more than one area within short period of time, care should be taken so that the hourly limit is not exceeded.In some clinical situations, the exposure to the room below can be the limiting factor in workload, especially for hospital buildings with short floor‐to‐floor distances that have thin concrete floors. However, for rooms with floor thicknesses of 25 cm or more, the exposure to the room below is of the same order as the exposures to the adjacent rooms, providing that the floor‐to‐floor height is at least 3.0 meters.Depending on the floor‐to‐floor distance and floor thickness, the predicted exposure levels in the room below the Mobetron can be comparable and even less than the exposure in the adjacent areas.The unpublished radiation survey data measured by Anna Petoukhova  was compared with calculated values using the data in this investigation. Almost all survey numbers are smaller than the predicted values indicating that, in practice, many OR walls will provide some stray X‐ray radiation attenuation, rather than none as assumed in this study.Several points which are above the predicted value have one common property: there is very thin wall or no wall between the Mobetron and survey meter. Therefore LPR was most likely affecting the measured exposure rate.The information in this investigation provides a basis for the determination of monitor unit‐based weekly workload and maximum patient treatment volumes for the Mobetron. Some site‐specific information is required to perform the workload calculations. Current investigation shows that special distribution of the radiation exposure varies insignificantly between the energies with no evident best or worst case. Therefore, any anticipated clinical energy mix will perform similarly relative to the results presented in the paper.The data and methodology demonstrate that for normal room dimensions, there generally will not be a restriction on patient load. The walls and the floor pose about equal concern for most situations that are encountered. If the areas around OR are occupied and non‐controlled, assuming standard building materials and distances, the facility may be restricted to 150 to 250 Gy per week. Normal patient loads of five to six patients per week, receiving approximately 10–20 Gy, including warm‐up, fit well within the confines of workload limitations calculated here. However, this conservative restriction can be averted if the occupancy of that area is less than one. The measurements and subsequent calculations clearly demonstrate that the Mobetron can be operated in a room with little or no additional shielding.The authors express their appreciation to Richard Simon, Kent Regal, Rick Kelly and James Ferrando for their assistance. This investigation was supported by IntraOp Medical Corp.


All lightning strokes generate electromagnetic pulses –atmospherics– which can travel over distances of thousands of kilometers. Night-side atmospherics show typical frequency dispersion signatures caused by sub-ionospheric propagation. Their analysis can be used to determine the distance to the source lightning, and therefore it represents a safe tool for investigation of distant thunderstorms, as well as for indirect observations of the lower ionosphere. However, such analysis has never been done on the dayside. Here we present the first results which show unusual daytime atmospherics with dispersion signatures originating from strong thunderstorms which occurred during winter months 2015 in the North Atlantic region. Using newly developed analysis techniques for 3-component electromagnetic measurements we are able to determine the source azimuth and to attribute these rare atmospherics to both positive and negative lightning strokes in northern Europe. We consistently find unusually large heights of the reflective ionospheric layer which are probably linked to low fluxes of solar X rays and which make the dayside subionospheric propagation possible. Although the atmospherics are linearly polarized, their dispersed parts exhibit left handed polarization, consistent with the anticipated continuous escape of the right-hand polarized power to the outer space in the form of whistlers. In the very low frequency (VLF) range below 30 kHz these electromagnetic pulses, called atmospherics, can propagate over thousands of kilometers from their source lightning. They travel inside the Earth-ionosphere waveguide which is formed by a conductive ground or sea on one side and by the lower edge of the ionospheric D-region on the other side5. Distances travelled by atmospherics are strongly dependent on the waveguide properties, primarily on the D-region reflectivity which exhibits significant diurnal, latitudinal, and seasonal variations. It also changes with varying solar activity, being prevalently controlled by the solar UV light and solar X-rays which ionize the neutral components in the D-region 6 during the day. The increased daytime ionization leads to a higher number of collisions with neutrals which result in low reflection heights, strong attenuation, and thereby short propagation paths of daytime atmospherics. VLF waves reflect from the lower ionosphere at an altitude of ∼60–70 km at midday but as high as ∼85–90 km at night8.It is known from the dawn of radio science9 an impulsive signal (in this case generated by a lightning discharge) excites different transmission modes. A zero-order mode travels in the waveguide at all frequencies but higher-order modes cannot propagate below their critical frequencies where their respective group velocities tend to zero. An atmospheric is then composed from these different waveguide modes. During the nighttime, many atmospherics exhibit a strong dispersion close to the critical frequencies of waveguide modes thanks to low attenuation and long propagation paths of electromagnetic VLF waves. These atmospherics are known as “tweeks” because of their typical sound when heard in a loudspeaker10. Figure According to the waveguide theory13 and their observation below a highly ionized daytime ionosphere has been thought impossible. Indeed, typical daytime observations show atmospherics without tweek signatures  close to Rustrel, France. We are using two perpendicular magnetic loop antennas with effective surfaces of 48 mth to 15th January 2015 for our study. At that time a sequence of severe winter thunderstorms hit Ireland, the UK, Norway, Denmark, Germany, and Poland. During this period we have selected VLF data which were recorded at least two hours after the sunrise and two hours before the sunset, so that we can be sure the signals were received under daytime conditions. This gave us 59–62 data records of 144 s for each day, obtained during approximately 5 daytime hours. We have chosen the strongest atmospheric in each data record and searched for the signatures of frequency dispersion close to the critical frequency of the first-order waveguide mode in their time-frequency spectrograms. We have found promising unusual signs of dispersion for some of these atmospherics . To measure their arrival azimuth we use a direction finding technique based on our 3-component measurement of electromagnetic fields (see Methods).d .Knowing the estimated propagation distances and arrival azimuths we can localize the source lightning strokes for the observed daytime tweeks. In 39 cases they were found in the region of the North-Atlantic thunderstorms  indicates a positive polarity of 10 strokes  polarized ones5 resulting in an increased anisotropy. Winter conditions are favorable for this phenomenon to happen as the reflection heights tend to be larger for larger solar zenith angles7.The ionospheric anisotropy is not significant for normal daytime conditions. To make it more significant, we need to increase the reflection heights and that is exactly what we observe in the analyzed cases. This increase of reflection heights leads to an unusually low daytime collision frequency and a sharper electron density profile8. Figure A remaining question is why the daytime tweek atmospherics haven’t been observed more often in winter thunderstorms. Here we need to discuss the variability of an important source of ionization of the ionospheric D region: X ray radiation linked to solar flaresvgn of the electromagnetic wave propagating in the nth waveguide mode can be written as a function of the critical frequency of the nth mode fcn and the frequency of the wave f 12:c is the speed of light. Assuming that waves at all frequencies are generated at the same time t0, they arrive to a propagation distance d at a time t = t0 + d/vgn. The expression for the frequency as a function of time then has two free parameters: the critical frequency fcn and the propagation distance d:τ = t − t0 − d / c is time relative to the arrival time of the initial return stroke signal (ground wave) which we assume to propagate at the speed of light. The reflection height h can be then calculated from the critical frequency:Above the critical frequencies of the Earth-ionosphere waveguide, the group velocity To analyze the behavior of the wave frequency of each observed tweek close to the critical frequency of the first waveguide mode we have selected one of the wave components which exhibited the most pronounced frequency dispersion in its time-frequency spectrogram. This always was the weaker of the two magnetic components: the southward magnetic component in 40 cases and the eastward magnetic component in 2 cases. The spectrograms of the electric field component did not show any signs of dispersion in our cases.19). This representation is constructed in the frequency domain by suppressing the negative frequency components. In the time domain this is equivalent to adding an imaginary part to the real signal,B(t)} denotes the Hilbert transform of the real signal B(t). A(t) is the instantaneous amplitude obtained as a modulus of the complex analytic signal, and the instantaneous frequency f(t) is obtained as the time derivative of the phase φ(t) of the analytical signal,We have selected 10 milliseconds (500 samples) time interval which starts between 0.3 and 0.8 millisecond after the dominant peak of the corresponding atmospheric. This peak usually follows the ground wave signal by a small fraction of a millisecond. In this interval we have used a technique based on the analytic representation of the measured signal  and their standard deviations. As the investigated tweek signals were often polluted by other weaker atmospherics, we have been gradually reducing the original data set by 50 samples in order to achieve a lowest possible chi-square value and at the same time to keep the total number of samples above 200. The final numbers of samples in the individual time intervals for the least squares fit varied from 200 to 350. The resulting nonlinear fits for two differently distant events (1529 and 2723 km) are plotted by red solid lines in Fig. We have used this estimated time evolution of instantaneous frequency as an input for a nonlinear least squares method to estimate two free parameters of the model in equation 20, their radiated electric field is oriented vertically, and the associated magnetic field is oriented horizontally and perpendicular to their propagation path. It means that our technique is based on an implicit assumption that the arrival azimuth of an atmospheric can be determined by measuring two horizontal magnetic field components and one vertical electric component of the incoming atmospheric. As its signal is very broadband, we use a predefined part of the frequency spectrum and we integrate the results over frequency.To estimate the arrival azimuth of the selected tweek atmospherics we have used a direction finding technique based on the measurement of three components of electromagnetic fields at a single station. Our basic assumption is that the detected atmospherics are predominantly composed of the Transverse Magnetic (TM) waveguide modes. The TM waveguide waves are preferentially excited by vertical lightning currentsfk ≤ 25 kHz, amplitudes Ak,E, Ak,S, and Ak,V, and phases φk,E, φk,S, and φk,V, respectively, for the eastward magnetic field component (E), southward magnetic field component (S), and vertical upward electric field component (V). For each frequency fk we then calculate angle αk using the amplitudes of both magnetic field components,As the first step the Fast Fourier Transform (FFT) is used for the selected time intervals of all three wave components sampled at 50 kHz to obtain a sum of sinusoidal complex signals with frequencies 21 we have chosen the frequency interval from fk1 = 7 kHz to fk2 = 13 kHz in which we determine the wave arrival azimuth. We calculate the weighted average angle α from appropriate angles αk with the respective weights wk defined as the absolute magnitudes of the magnetic field in the horizontal plane,Since the major part of the energy of atmospherics is concentrated in a several kHz wide frequency band around 10 kHzAk,E and Ak,S are nonnegative; the values of α are contained between 0° and 90°. To obtain full arrival azimuths between −180° and +180°, we use the relative phases between all three components  of the investigated signals,As the amplitudes For an isolated linearly polarized atmospheric unpolluted by any background noise or other interfering signals we would expect all components of the wave to have their relative phases equal to either 0° or ±180° in the whole range of frequencies. This assumption is not entirely satisfied in real conditions. Due to noisy background, interferences, propagation, and instrumental effects the resulting relative phases have deviated from their ideal values by 5–30°. Therefore, we round the relative phase values to the nearest multiple of 180° to retrieve the ideal values. This robust algorithm accompanied by the information about all polarization reversals of the signal inside our instrumentation was used to determine the correct quadrant of possible wave arrival azimuths and to estimate the azimuth of arrival of observed atmospherics.22. Their polarity can be therefore recognized by the polarity of the initial ground wave pulses in waveforms of the vertical electric field component from atmospherics generated by these strokes.Positive and negative lightning discharges are initiated in different thundercloud charge centers. The charge which is then being transferred in lightning channels during the return stroke phase is moving in opposite directions in cases of negative or positive lightning discharges22. However, the experimental determination of the polarity of ground wave pulses is sometimes difficult since the amplitudes of the sky wave pulses (reflected from the bottom of the ionosphere) start to be comparable with the ground wave amplitudes at distances above 500 km from the source lightning and they dominate the waveform recordings from distances above 1000 km. At distances larger than about 2000 km the ground wave might be already attenuated to the noise level23 in weak cases, and the first and the second sky wave (one or two reflections) become similarly strong. Nevertheless, as we only selected the strongest cases for this study, we believe that we were able to identify the polarity of ground waves for all 42 analyzed source lightning strokes which generated the observed tweeks. Most often, the strongest pulse in the sequence was found at the position of the first or the second sky wave pulse. The absolute amplitude of the weakest ground wave peak in our data set was still at 7% of the corresponding largest peak amplitude and well above the noise level.As we are using a sign convention with a positive electric field pointing upward, we can expect negative ground wave pulses for negative strokes and positive ones for positive strokeshttp://bleska.ufa.cas.cz/lsbb/storage/elm/.The data used in this study are at