Thread Region Research Articles

Evolution of corrosion degradation in galvanised steel bolts exposed to a tropical marine environment

The time-dependent degradation of galvanised steel bolts subjected to marine atmospheric exposure for a maximum period of 2 years in the Wenchang marine environment of Hainan province, South China, was investigated. The results showed that the zinc coating used as a protective surface finish deteriorated quickly due to the harsh environmental conditions. The deterioration of the zinc coating resulted in premature corrosion of the underlying steel substrate as early as 6 months. The main Zn corrosion products found at the initial exposure time were simonkollite (Zn5(OH)8Cl2·H2O), hydrozincite (Zn5(OH)6(CO3)2), and zincite (ZnO). At subsequent exposure times, major steel corrosion products such as lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite (Fe3O4), and maghemite (γ-Fe2O3) were detected. Fe3O4/γ-Fe2O3 was consistently found in the rust formed at both the exposed and crevice thread regions between 6 and 24 months of exposure. Based on the geometry of the bolt fastener, the corrosion rate and phase composition distribution varied between the two regions. Differences in oxygen exposure levels, corrosion kinetics, and electrochemical stability of the corrosion products were primary factors in these distinctive corrosion behaviours.

Investigating the role of SERBP1 in translation.

Idle ribosomes are inactive 80S monosomes that lack mRNA and are common throughout eukaryotes. In yeast, they promote starvation recovery and translational reactivation. In metazoan, their physiological functions and the mechanisms governing their abundance are unclear. Current hypotheses posit that they play a role in fine tuning protein synthesis under conditions requiring tight regulation such as cell development and plasticity. Previously, we determined cryo-EM structures of idle ribosomes containing serpine 1 mRNA binding protein (SERBP1) and phosphorylated eukaryotic elongation factor 2 (p-eEF2). SERBP1 binds to the 40S head via a small helix and threads through the mRNA channel, where it interacts with eEF2. Here, we term these regions ‘anchor’ and ‘thread’, respectively. Stimulation of eEF2 kinase (eEF2K) increases the abundance of SERBP1/p-eEF2 idle ribosomes and prevents their recycling in vitro. SERBP1 also regulates the stability of specific mRNAs and contains motifs that drive phase separation. We propose that different regions of SERBP1 mediate its functions in translation and localization in liquid phase separation. We designed structure-informed truncations and mutations and examined their effect on protein synthesis in an in vitro translation system. We found that recombinant full-length SERBP1 strongly inhibits translation. A C-terminal truncation including the thread and anchor regions shows a similar inhibitory effect, attenuated upon mutating the binding sites with eEF2. The SERBP1 anchor alone does not affect protein synthesis. eEF2K strongly inhibits translation and this effect is not enhanced in the presence of the anchor. Collectively, our data suggest that the SERBP1 thread and specifically the residues interacting with eEF2 are critical for attenuation of protein synthesis, likely by promoting the formation of idle ribosomes. Further studies will illuminate if other SERBP1 regions are implicated in this process and in phase separation, and if eEF2K acts synergistically to inhibit translation.

Modified Z-phase formation in a 12% Cr tempered martensite ferritic steel during long-term creep

The formation of modified Z-phase in a 12Cr1MoV (German grade: X20) tempered martensite ferritic (TMF) steel subjected to interrupted long-term creep testing at 550°C and 120 MPa was investigated. Quantitative volumetric measurements collected from thin-foil and extraction replica samples showed that modified Z-phase precipitated in both the uniformly-elongated gauge (fv: 0.23 ± 0.02 %) and thread regions (fv: 0.06 ± 0.01 %) of the sample that ruptured after 139 kh. The formation of modified Z-phase was accompanied by a progressive dissolution of MX precipitates, which decreased from (fv: 0.16 ± 0.02%) for the initial state to (fv: 0.03 ± 0.01%) in the uniformly-elongated gauge section of the sample tested to failure. The interparticle spacing of the creep strengthening MX particles increased from (λ3D: 0.55 ± 0.05 μm) in the initial state to (λ3D: 1.01 ± 0.10 μm) for the uniformly-elongated gauge section of the ruptured sample, while the thread region had an interparticle spacing of (λ3D: 0.60 ± 0.05 μm). The locally deformed fracture region had an increased phase fraction of modified Z-phase (fv: 0.40 ± 0.20%), which implies that localised creep-strain strongly promotes the formation of modified Z-phase.

Relationship between thread depth and fixation strength in cancellous bone screw

BackgroundClarifying the effect of each parameter of screw design on its fixation strength is critical in the development of any type of screw. The purpose of this study was to clarify the relationship between the thread depth and fixation strength of metal screws for cancellous bone. MethodsNine types of custom-made screws with the only changed variable being the thread depth were manufactured. Other elements were fixed at a major diameter of 4.5 mm, a thread region length of 15 mm, a pitch of 1.6 mm, and a thread width of 0.20 mm. The pull-out strength and insertion torque of each screw were measured for each of two foam-block densities (10 or 20 pcf). The correlation between the thread depth of the screw and the mechanical findings were investigated with single regression analysis. ResultsRegardless of the foam-block density, the pull-out strength significantly increased as the thread depth increased from 0.1 mm to 0.4 mm; after that, the increase was more gradual (p < 0.01, respectively). The relationship between the thread depth and insertion torque was similar. In addition, the insertion torque tended to be more strongly affected by screw depth than the pull-out strength (2.6 times at 20 pcf and 1.4 times at 10 pcf). ConclusionsThe pull-out strength of 4.5-mm-diameter metal screws in a cancellous bone model was found to be biphasic, although linearly correlated with the change in screw depth in both phases. The boundary of the correlation was 0.4 mm regardless of the density of the bone model, with the effect of screw depth on pull-out strength beyond that being small in comparison.

Extensible and self-recoverable proteinaceous materials derived from scallop byssal thread

Biologically derived and biologically inspired fibers with outstanding mechanical properties have found attractive technical applications across diverse fields. Despite recent advances, few fibers can simultaneously possess high-extensibility and self-recovery properties especially under wet conditions. Here, we report protein-based fibers made from recombinant scallop byssal proteins with outstanding extensibility and self-recovery properties. We initially investigated the mechanical properties of the native byssal thread taken from scallop Chlamys farreri and reveal its high extensibility (327 ± 32%) that outperforms most natural biological fibers. Combining transcriptome and proteomics, we select the most abundant scallop byssal protein type 5-2 (Sbp5-2) in the thread region, and produce a recombinant protein consisting of 7 tandem repeat motifs (rTRM7) of the Sbp5-2 protein. Applying an organic solvent-enabled drawing process, we produce bio-inspired extensible rTRM7 fiber with high-extensibility (234 ± 35%) and self-recovery capability in wet condition, recapitulating the hierarchical structure and mechanical properties of the native scallop byssal thread. We further show that the mechanical properties of rTRM7 fiber are highly regulated by hydrogen bonding and intermolecular crosslinking formed through disulfide bond and metal-carboxyl coordination. With its outstanding mechanical properties, rTRM7 fiber can also be seamlessly integrated with graphene to create motion sensors and electrophysiological signal transmission electrode.

Dye and metal ion adsorption ability of Asian green mussel byssus thread complex; their microscopic and thermal property characterization

ABSTRACT Various physical, chemical, and biological factors act as pollutants and cause deleterious effects on the environment and living organisms. Several researchers are developing eco-friendly good adsorbent from agriculture waste materials for pollutant removal, especially aromatic dyes and heavy metal removal. We used the Asian green mussel byssus thread, a natural mariculture waste product for the removal of aromatic dyes (methylene blue and eosin Y) and heavy metals (zinc, copper, iron, mercury and lead). We documented the dynamicity of byssus thread dye and metal removal at different pH (pH 2–10) and different concentrations. The highest amount of metal removal was observed at pH 6.0, and the dye removal efficacy is related to the property of the dye (i.e. anionic or cationic dye). The byssus thread had a natural fluorescent property upon UV-excitation; however, microscopic examination revealed that metal and dye coordination significantly alter the byssus plaque region’s physical and chemical property rather than the thread regions. It was further confirmed by using DSC and TGA characterization of de-metaled and metal-treated byssus thread complex. We concluded that Perna viridis byssus thread could be used as a strong adsorbent for dye and metal removal from the water.

One-dimensional prominence threads

Context. Threads are the building blocks of solar prominences and very often show longitudinal oscillatory motions that are strongly attenuated with time. The damping mechanism responsible for the reported oscillations is not fully understood yet. Aims. To understand the oscillations and damping of prominence threads we must first investigate the nature of the equilibrium solutions that arise under static conditions and under the presence of radiative losses, thermal conduction, and background heating. This provides the basis to calculate the eigenmodes of the thread models. Methods. The non-linear ordinary differential equations for hydrostatic and thermal equilibrium under the presence of gravity are solved using standard numerical techniques and simple analytical expressions are derived under certain approximations. The solutions to the equations represent a prominence thread, a dense and cold plasma region of a certain length that connects with the corona through a prominence corona transition region (PCTR). The solutions can also match with a chromospheric-like layer if a spatially dependent heating function localised around the footpoints is considered. Results. We have obtained static solutions representing prominence threads and have investigated in detail the dependence of these solutions on the different parameters of the model. Among other results, we show that multiple condensations along a magnetic field line are possible, and that the effect of partial ionisation in the model can significantly modify the thermal balance in the thread, and therefore their length. This last parameter is also shown to be comparable to that reported in the observations when the radiative losses are reduced for typical thread temperatures.

Analysis of Surface Morphology and Elemental Composition on Zirconia Implants Before and After Photofunctionalization by Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy - An In vitro Study.

Background:The purpose of this study is to analyze the surface morphology and elemental composition of zirconia implants before and after photofunctionalization.Materials and Methods:Ten zirconia implants (white sky implant system– Bredent Company) five each in the study group and control group was taken. Study group samples were treated with ultraviolet light for 48 h. Microstructured surface of the study and control group blanks at abutment and thread regions were documented by Scanning Electron Microscope The semi-quantitative element composition was analyzed using Energy-dispersive X-ray (EDX) spectrum.Results:SEM images of the study and control group divulged a varied array of topographical configuration of the abutment area and thread region at different magnifications. At low magnification, both study and control group revealed plain compact surface and wavy porous area, whereas higher magnification showed dense grainy regions of various sizes and intensities disrupted by pores. EDX spectrum analysis for elemental composition showed increased oxygen concentration in the study group (42.8%) than the control group (29.09%), whereas carbon concentration was lower in photofunctionalized group (34.34%) than in the control group (45.41%).Conclusion:In zirconia implants, photofunctionalization is a viable method to effectively enhance the surface topography and hydrophilicity of bone-implant interface.

Analysis of Surface Roughness and 3D Scanning Topography of Zirconia Implants Before and After Photofunctionalisation by 3D Optical Profilometry- An Invitro Study

Introduction: Zirconia is considered as an alternative material for the fabrication of implants. Surface roughness of the implant plays a fundamental role in the initial bone formation. The rationale of using 3D optical profilometry in this study was to evaluate the surface roughness of the zirconia implants before and after Ultraviolet (UV) photofunctionalisation. Also, Moreso 3D optical instruments have a better resolution than the mechanical ones like Atomic Force Microscopy (AFM). Aim: To analyse the surface roughness and topography of zirconia implants after photofunctionalisation using optical profilometry. Materials and Methods: This is an in-vitro study conducted over a period of six months from March 2020 to August 2020. Ten commercially machined Zirconia implants, five each in study and control group, were micro analysed at three different regions (abutment, thread and crest) by optical profilometry. Study group was surface treated by UV radiation for 48 hours. Quantitative morphometric analysis was done between two groups and p-value less than 0.05 was considered statistically significant. The statistical test applied in this study was independent t-test. Results: Scanning micrographs of the study group revealed highest density of summits contributing to increased surface area in the study group. Quantitative analysis of surface roughness showed statistically significant higher mean roughness parameter for photofunctionalised implants in abutment, crest and thread region (p&lt;0.05). Conclusion: Photofunctionalisation is a potentially synergistic technique in producing textured zirconia implants.

An In Vitro Analysis of Sodium Hypochlorite Decontamination for the Reuse of Implant Healing Abutments.

The reuse of healing abutments (HAs) has become common practice in implant dentistry for economic concerns and the aim of this in vitro study was to assess the effect of sodium hypochlorite (NaOCl) in decontamination of HAs. A total of 122 HAs (used and sterilized [n = 107]; new [n = 15]) were procured from 3 centers, of which 3 samples were discarded due to perforation in the sterilization pouch. For sterility assessment, the used HAs (n = 80) were cultured in Brain Heart Infusion Broth (BHI) and potato dextrose agar (PDA); bacterial isolates were identified in 7 samples. Also, 24 used HAs were stained with phloxine B, photographed, and compared to new HAs (n = 5). A scanning electron microscope (SEM) assessed the differences between 2 sets of HAs, after which the 7 contaminated HAs along with 24 used HAs from staining experiment (total: 31) were subsequently treated with sodium hypochlorite (NaOCl) and SEM images were observed. About 8.75% of HAs tested positive in bacterial culture; Streptococcus sanguis, Dermabacter hominis, Staphylococcus haemolyticus, and Aspergillus species were isolated. Phloxine B staining was positive for used and sterilized HAs compared to controls. The SEM images revealed deposits in the used HAs and although treatment with NaOCl eliminated the contamination of cultured HAs, the SEM showed visible debris in the HA thread region. This in vitro study concluded that SEM images showed debris in used HAs at screw-hole and thread regions even though they tested negative in bacterial culture. The treatment with NaOCl of used HAs showed no bacterial contamination but the debris was observed in SEM images. Future studies on the chemical composition, biological implications, and clinical influence is warranted before considering reuse of HAs.

A spectroscopic, photometric, polarimetric, and radio study of the eclipsing polar UZ Fornacis: the first simultaneous SALT and MeerKAT observations

ABSTRACT We present phase-resolved spectroscopy, photometry, and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at ∼4500, 6000, and 7700 Å, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of ∼57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source that has a peak flux density of 30.7 ± 5.4 $\mu$Jy beam−1 at 1.28 GHz at the position of UZ For.

Alloy 718 Subsea Bolt in Relation to Surface Cracking: A Microstructural Perspective

The brittle fracture mode close to the surface of Inconel 718 subsea bolts is closely related to their nanostructure. When the bolts are used subsea under cathodic protection, hydrogen evolves. Intergranular precipitates and points of intersection of slip lines always held responsible for hydrogen enhanced decohesion. However, thus far, little attention has been paid to the bolts manufacturing method and to the characterization of the role of subsurface oversized nanoprecipitates on transgranular surface cracking. As-received subsea bolts were analyzed using multi-scale observation techniques such as focused ion beam milling, scanning electron microscopy, transmission electron microscopy, and in-air strain rate tensile tests. The results further demonstrated that under identical API aging, there was a difference in the morphological precipitation and strength of 718 as a bolt and rectangular billet. For the 718 rectangular billets, discrete intergranular stable δ/MC carbides precipitate and only γ' of 10 - 20 nm was observed for the bulk and subsurface. Whereas, for the CRA subsea bolt, γ' was approximately 30 nm, γ" was 30 - 50 nm for the bulk (370 HV); γ' was approximately 50 nm and γ" was 50 - 100 nm at subsurface (400 HV). As-received subsea bolts were investigated at subsurface (10 μm from the surface) at the thread and shank region, which revealed transgranular sheared oversized ~50 nm γ' (with dislocation networks) and metastable γ" > 100 nm particles, respectively. Thus, an effort was made to develop the hydrogen-assisted surface cracking theory for bolts.

A Finite Element Analysis to Compare Stress Distribution on Extra-Short Implants with Two Different Internal Connections.

Background: The goal of this study was to analyze the stress distribution on two types of extra-short dental implants with 5 mm of length: An internal hexagon (IH) and morse taper connection (MT). Methods: The three-dimensional model was composed of trabecular and cortical bone, a crown, an extra-short dental implant and their components. An axial load of 150 N was applied and another inclined 30° with the same magnitude. Results: Stress concentrations on the IH implant are observed in the region of the first threads for the screw. However, in the MT implant the highest stress occurs at the edges of the upper implant platform. Conclusions: In view of the results obtained in this study the two types of prosthetic fittings present a good stress distribution. The Morse taper connections presented better behavior than the internal in both loading configurations.

Determination of the critical socket depths of 10.9 and 8.8 grade M8 bolts with hexagonal socket form

In this work, the effect of various socket depths of fasteners was investigated for the sake of weight reduction. M8x1.25 × 50 Full Thread (FT) bolts with 10.9 and 8.8 grade were examined in detail. The finite element simulations were performed by using SIMUFACT Forming Software. Empirical studies including fatigue and torque-tension experiments were conducted with the bolts having various socket depths. In addition, the effect of washer as used in most assembly conditions was investigated. One of the analytical methods used in the literature was also employed to compare the results obtained by the numerical and experimental methods. Based on the results obtained in this study, critical socket depths leading to the shift of failures from the thread region to head region were obtained for the investigated M8x1.25 × 50 FT bolts with 10.9 and 8.8 grades. The experimental results were compared with the analytical model and found that the analytical model underestimated the critical socket depths for both 10.9 and 8.8 grade bolts.

Intelligent detection method for tapping omitting of internal thread based on computer vision

Tapping plays an important role in machining internal thread, whereas tapping omitting is inevitable in automated mass production. In this paper, a method for interior thread detection is presented for its efficiency, stability and robustness. Some key technologies such as imaging scheme and image processing algorithms were studied on the basis of the self-designed online detecting device. Firstly, the global threshold segmentation algorithm and local region growing segmentation algorithm are combined to precisely segment the imaging region of screw holes, while the imaging region of thread region is acquired based on the previous orientation. Then, the shape descriptors of the hole and texture descriptors of thread region are computed, respectively. And each descriptor's attribute importance is obtained using rough set. Finally, based on significant classification descriptors, semantic recognition of tapping omitting is achieved by heuristic rules. The experiment shows that the proposed classification algorithm using semantic features can identify the internal thread. The average detection time is 0.256 s, the detection accuracy of tapping omitting is 95.88%, and the detection accuracy of tapping thread is 100%.

Intelligent detection method for tapping omitting of internal thread based on computer vision

Tapping plays an important role in machining internal thread, whereas tapping omitting is inevitable in automated mass production. In this paper, a method for interior thread detection is presented for its efficiency, stability and robustness. Some key technologies such as imaging scheme and image processing algorithms were studied on the basis of the self-designed online detecting device. Firstly, the global threshold segmentation algorithm and local region growing segmentation algorithm are combined to precisely segment the imaging region of screw holes, while the imaging region of thread region is acquired based on the previous orientation. Then, the shape descriptors of the hole and texture descriptors of thread region are computed, respectively. And each descriptor's attribute importance is obtained using rough set. Finally, based on significant classification descriptors, semantic recognition of tapping omitting is achieved by heuristic rules. The experiment shows that the proposed classification algorithm using semantic features can identify the internal thread. The average detection time is 0.256 s, the detection accuracy of tapping omitting is 95.88%, and the detection accuracy of tapping thread is 100%.

Analysis of risk factors of 19 fractured implants

Objective: To analyze the incidence and possible risk factors of 19 fractured implants out of 8 468 implants in 3 184 cases. Methods: During the 22-year clinical practice, clinical records of 18 patients with 19 fractured implants in 3 184 cases with 8 468 implants were analyzed to determine the following factors: location of the fractured implants, prosthodontics option, date of implant fracture, dimensions of fractured implants, complications prior to implant fracture and parafunctional habit. An evaluation of fractured implants was performed to identify possible factors that may predispose an implant to a higher risk of fracture. Results: Overall, the average duration of service of the implants was (7.0±4.5) years. Implant fracture occurred in 7 Camlog implants, 7 Nobel replace implants, 3 Ankylos implants and 2 Brånemark implants. No Thommen implant fractures were recorded. Amongst the 19 fractured implants, 8 occurred at the thinnest wall portion of the implant neck, 8 at the end of screw and 3 at the self-tapping thread region. All fractures were observed after functional loading. Furthermore, 9/19 (47.4%) of fractures occurred in the maxilla, indicating similar incidence rates in both arches (P=0.065). Most of fractures (16/19) occurred in the molar region and 18/19 in single implant-supported restorations. Totally 17 cases had received metal occlusal restorations. In 6 cases (35.5%), previous bone destruction apically extending to the level of implant fracture was documented before any clinical signs of fracture. Three fractured implants were removed and simultaneously re-implanted with larger-diameter implants, while the rest of the cases were left to heal, followed by a second-stage surgery. Conclusions: Within the limitation of this analysis, the study demonstrated that appropriate implant-abutment connection design, implant diameter, prosthetic strategy and bone resorption are crucial to the long-term performance of implants. There is no significant difference of fractures rates in both archs.

A user‐assisted thread‐level vulnerability assessment tool

SummaryThe system reliability becomes a critical concern in modern architectures with the scale down of circuits. To deal with soft errors, the replication of system resources has been used at both hardware and software levels. Since the redundancy causes performance degradation, it is required to explore partial redundancy techniques that replicate the most vulnerable parts of the code. The redundancy level of user applications depends on user preferences and may be different for the users with different requirements. In this work, we propose a user‐assisted reliability assessment tool based on critical thread analysis for redundancy in parallel architectures. Our analysis evaluates the application threads of a parallel program by considering their criticality in the execution and selects the most critical thread or threads to be replicated. Moreover, we extend our analysis by exploring critical regions of individual threads and execute redundantly only those regions to reduce redundancy overhead. Our experimental evaluation indicates that the replication of the most critical thread improves the system reliability more (up to 10% for blackscholes application) than the replication of any other thread. The partial thread replication based on critical region analysis also reduces the vulnerability of the system by considering a fine‐grained approach.

Unravelling the effect of macro and microscopic design of dental implants on osseointegration: a randomised clinical study in minipigs

Several dental implants are commercially available and new prototype design are constantly being fabricated. Nevertheless, it is still unclear what parameters of the design affect most the osseointegration of dental implants. The purpose of this study is to assess the effects of the microscopic and macroscopic design of dental implants in the osseointegration by comparing three macroscopic designs (Straumann tissue level (STD), essential cone (ECD) and prototype design (PD)) and six surface treatments. A total of 96 implants were placed in 12 minipigs. The implant stability quotient (ISQ), was assessed at the time of implantation, as well as at 2, 4 and 8 weeks. Histomorphometric and statistical analyses were conducted at the different sacrifice times, being 2, 4 and 8 weeks, to analyse the bone to implant contact (BIC), the bone area density (BAT) and the density of bone outside the thread region (ROI). The macroscopic design results showed higher ISQ values for the ECD, whereas the histomorphometric analysis showed higher ossoeintegration values for the STD. Regarding the microscopic design, both Sandblasted plus acid etching (hydrochloric/sulphuric acid) in a nitrogen atmosphere (SLActive) and Shot-blasted or bombarded with alumina particles and posterior alkaline immersion and thermal treatment (ContacTi) showed superior results in terms of osseointegration and reduced the osseointegration times from 8 weeks to 4 weeks compared to the other analysed surfaces. In conclusion, each of the macroscopic and microscopic designs need to be taken into account when designing novel dental implants to enhance the osseointegration process.

The Formation of a Small-Scale Filament After Flux Emergence on the Quiet Sun

We present observations of the formation process of a small-scale filament on the quiet Sun during 5-6 February 2016 and investigate its formation cause. Initially, a small dipole emerged and its associated arch filament system was found to reconnect with overlying coronal fields accompanied by numerous EUV bright points. When bright points faded out, many elongated dark threads formed bridging the positive magnetic element of dipole and external negative network fields. Interestingly, an anti-clockwise photospheric rotational motion (PRM) set in within the positive endpoint region of newborn dark threads following the flux emergence and lasted for more than 10 hours. Under the drive of the PRM, these dispersive dark threads gradually aligned along the north-south direction and finally coalesced into an inverse S-shaped filament. Consistent with the dextral chirality of the filament, magnetic helicity calculations show that an amount of negative helicity was persistently injected from the rotational positive magnetic element and accumulated during the formation of the filament. These observations suggest that twisted emerging fields may lead to the formation of the filament via reconnection with pre-existing fields and release of its inner magnetic twist. The persistent PRM might trace a covert twist relaxation from below photosphere to the low corona.