Coatings for graphite fibers

Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature

Study of high resistance inorganic coatings on graphite fibers

Coatings made of boron, silicon carbide, silica, and silica-like materials were studied to determine their ability to increase resistance of graphite fibers. The most promising results were attained by chemical vapor depositing silicon carbide on graphite fiber followed by oxidation, and drawing graphite fiber through ethyl silicate followed by appropriate heat treatments. In the silicon carbide coating studies, no degradation of the graphite fibers was observed and resistance values as high as three orders of magnitude higher than that of the uncoated fiber was attained. The strength of a composite fabricated from the coated fiber had a strength which compared favorably with those of composites prepared from uncoated fiber. For the silica-like coated fiber prepared by drawing the graphite fiber through an ethyl silicate solution followed by heating, coated fiber resistances about an order of magnitude greater than that of the uncoated fiber were attained. Composites prepared using these fibers had flexural strengths comparable with those prepared using uncoated fibers, but the shear strengths were lower

Ground Plane and Near-Surface Thermal Analysis for NASA's Constellation Program

Most spacecraft thermal analysis tools assume that the spacecraft is in orbit around a planet and are designed to calculate solar and planetary fluxes, as well as radiation to space. On NASA Constellation projects, thermal analysts are also building models of vehicles in their pre-launch condition on the surface of a planet. This process entails making some modifications in the building and execution of a thermal model such that the radiation from the planet, both reflected albedo and infrared, is calculated correctly. Also important in the calculation of pre-launch vehicle temperatures are the natural environments at the vehicle site, including air and ground temperatures, sky radiative background temperature, solar flux, and optical properties of the ground around the vehicle. A group of Constellation projects have collaborated on developing a cohesive, integrated set of natural environments that accurately capture worst-case thermal scenarios for the pre-launch and launch phases of these vehicles. The paper will discuss the standardization of methods for local planet modeling across Constellation projects, as well as the collection and consolidation of natural environments for launch sites. Methods for Earth as well as lunar sites will be discussed

Coatings for Graphite Fibers

Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak

The occurrence of postoperative vertigo after CI

Background. The incidence of postoperative vertigo after cochlear implantation (CI) varies a lot in the literature. The aim of this work was to investigate both subjective complaints of vertigo before and after cochlear implantation and related it to to the preoperative vestibular function, the surgical procedure and to the position of CI at the postoperative neuroradiological study. Methods. Retrospective cohort study of adult CI series operated by the same surgeon (DZ) over the last 3 years. (N= 107). Sixty-six subjects (38 F; 28 M), aged from 21 to 78 years old were included in the study, lasting 83 CI. The outcomes of the pre-operative vestibular assessment were extracted from the database of the Vestibular Disorders Unit of the tertiary referral University Hospital of Milano from 1992 to 2018 (N=557). Post-operative presence/absence of vestibular disorders was analyzed and related to the preoperative vestibular examination and to the flat-panel computed tomography (FPCT) findings. Results: The patients were divided by age and by the presence of vestibular response of the operated ear measured by videoculography, caloric testing and video-impulse test. Sensorial analysis by static posturography was also included. The incidence of postoperative vertigo was higher in patients > 65 years old (36.3% vs 20.4%, p=0.03). Postoperative vertigo did not result related to the surgical procedure. The results are discussed with the review of the literature. Conclusion: Our results confirm the importance of vestibular testing in CI recipients, in order to better counsel the patient on the foreseeable post-operative course and to identify those patients who will need a vestibular rehabilitation

Comparison of intrascalar location of straight vs perimodiolar electrode array by flat-panel computerized tomography

Introduction, One of the fields of technological advancement in cochlear implants (CI) pursued by all manufacturers is the development of less traumatic electrodes that can conform to the anatomy of the cochlea, and possibly enhance the outcomes. Recently, a slim precurved perimodiolar electrode with an insertion guidance sleeve has been designed in order to facilitate the insertion and to avoid the inter-scalar dislodgement that frequently occurs at the first basal turn. Aim of this study was to evaluate the intracochlear position of different Nucleus electrode arrays in aduld and pediatric CI recipients by means of flat-panel volume computerized tomography (FPCT). Methods, Fifty-six CI recipients (37 females, 19 males), 1 to 80 years of age, operated by the same surgeon with the same technique, were included. All underwent FPCT with a C-arm angiographic system including a digital flat panel detector 30 x 40 cm, with a source-to-image-receptor distance of 120cm. The imaging assessment was performed the day after surgery in all cases. Sequential and simultaneous CI were included and a total of 68 ears have been analyzed. The primary objective was to identify the scalar location of the array (completely in scala tympani vs. partially dislodged in scala vestibuli) and the site of dislocation. Secondarily, we measured the medial-lateral position within the scala, the insertion depth (mm and angles). The FPCT findings were also contrasted with the type of cochleostomy (round window (RW), extended RW, promontorial) and with the residual hearing preservation. Results, Fifty-nine ears were implanted with a perimodiolar electrode, either Nucleus CI532 (n=45) or a CI412 / CI512 Contour Advance (n=14), while 9 received a straight one (Nucleus CI422/CI522). A RW approach was performed more frequently (41 out of 45 = 91.1 %) with CI532 than with the other arrays (10 out of 23 = 43.5%). Inferior and/or anterior cochleostomy were never performed. The CI532 showed the most consistent and reliable intrascalar position, close to the modiolus and in the scala tympani. Scala vestibuli dislodgement was observed in (14.3%) of the Contour Advance electrodes and in (6.7%) of the CI532. Pre-operative residual hearing was preserved within 10 dB HL in 62% of the cases. Conclusions: the CI532 electrode array achieved the most consistent and reliable perimodiolar location by FPCT; in our small series it appeared to be dislodged in the scala tympani in the minority of cases

MR Imaging in Sudden Sensorineural Hearing Loss. Time to Talk

SUMMARY: Sudden sensorineural hearing loss is defined as acute hearing loss of the sensorineural type of at least 30 dB over 3 contiguous frequencies that occurs within a 72-hour period. Although many different causative factors have been proposed, sudden sensorineural hearing loss is still considered "idiopathic" in 71%–85% of cases, and treatments are empiric, not based on etiology. MR imaging implemented with a 3D FLAIR sequence has provided new insights into the etiology of sudden sensorineural hearing loss. Herein, we review the current management trends for patients with sudden sensorineural hearing loss, from the initial clinical diagnosis to therapeutic strategies and diagnostic work-up. We focused primarily on MR imaging assessment and discuss the relevance that MR imaging findings might have for patient management, pointing out different perspectives for future clinical research

Genetic and epigenetic factors of takotsubo syndrome: A systematic review

Takotsubo syndrome (TTS), recognized as stress’s cardiomyopathy, or as left ventricular apical balloon syndrome in recent years, is a rare pathology, described for the first time by Japanese researchers in 1990. TTS is characterized by an interindividual heterogeneity in onset and progression, and by strong predominance in postmenopausal women. The clear causes of these TTS features are uncertain, given the limited understanding of this intriguing syndrome until now. However, the increasing frequency of TTS cases in recent years, and particularly correlated to the SARS-CoV-2 pandemic, leads us to the imperative necessity both of a complete knowledge of TTS pathophysiology for identifying biomarkers facilitating its management, and of targets for specific and effective treatments. The suspect of a genetic basis in TTS pathogenesis has been evidenced. Accordingly, familial forms of TTS have been described. However, a systematic and comprehensive characterization of the genetic or epigenetic factors significantly associated with TTS is lacking. Thus, we here conducted a systematic review of the literature before June 2021, to contribute to the identification of potential genetic and epigenetic factors associated with TTS. Interesting data were evidenced, but few in number and with diverse limitations. Consequently, we concluded that further work is needed to address the gaps discussed, and clear evidence may arrive by using multi-omics investigations

MR Imaging in Menière Disease: Is the Contact between the Vestibular Endolymphatic Space and the Oval Window a Reliable Biomarker?

BACKGROUND AND PURPOSE: No reliable MR imaging marker for the diagnosis of Meniere disease has been reported. Our aim was to investigate whether the obliteration of the inferior portion of the vestibule and the contact with the stapes footplate by the vestibular endolymphatic space are reliable MR imaging markers in the diagnosis of Meniere disease. MATERIALS AND METHODS: We retrospectively enrolled 49 patients, 24 affected by unilateral sudden hearing loss and 25 affected by definite Meniere disease, who had undergone a 4-hour delayed 3D-FLAIR sequence. Two readers analyzed the MR images investigating whether the vestibular endolymphatic space bulged in the third inferior portion of the vestibule contacting the stapes footplate. This sign was defined as the vestibular endolymphatic space contacting the oval window. RESULTS: We analyzed 98 ears: 27 affected by Meniere disease, 24 affected by sudden sensorineural hearing loss, and 47 that were healthy. The vestibular endolymphatic space contacting the oval window showed an almost perfect interobserver agreement (Cohen κ = 0.87; 95% CI, 0.69–1). The vestibular endolymphatic space contacting oval window showed the following: sensitivity = 81%, specificity = 96%, positive predictive value = 88%, and negative predictive value = 93% in differentiating Meniere disease ears from other ears. The vestibular endolymphatic space contacting the oval window showed the following: sensitivity = 81%, specificity = 96%, positive predictive value = 96%, negative predictive value = 82% in differentiating Meniere disease ears from sudden sensorineural hearing loss ears. CONCLUSIONS: The vestibular endolymphatic space contacting the oval window has high specificity and positive predictive value in differentiating Meniere disease ears from other ears, thus resulting in a valid tool for ruling in Meniere disease in patients with mimicking symptoms

Analysis of polymorphisms Leiden Factor V G1691A and prothrombin G20210A as risk factors for acute myocardial infarction.

Thrombotic risk increases in elderly, therefore, the understanding of the genetic predisposition of hypercoagulability could make the difference in the prevention of venous and/or arterial thrombotic events. Laboratory evaluation of hyperfibrinogenemia, increased Factor VII levels, antiphospholipid antibodies presence and hyperhomocysteinemia are considered to have a consistent high predictivity for arterial thrombophilic diseases. Anyway, a large debate exists on the validity of testing Leiden Factor V (FV) G1691A and/or prothrombin (FII) G20210A polymorphisms in patients affected by arterial thrombotic diseases, despite of the several observations described. Here we report data strongly suggesting that at least the FII G20210A polymorphism might be considered an important risk factor for acute myocardial infarction in aged patients (55-80 years old). On the other hand, in spite of a not different genotypic and allelic distribution for the Leiden FV G1691A mutation, the presence of one or both the two polymorphisms is significantly higher among cases than in controls. In conclusion, our data suggest that FII G20210A and/or Leiden FV might be involved as risk factor for arterial disorders in about 5% of old subjects, justifying the opportunity of a genetic screening and an eventual preventive treatment, in particular in old subjects in which other and major risk factors, as hypertension and atherosclerosis, are detected