Piece Of Teflon Research Articles

The polarity of a plastic rod and a glass rod at contact charging

This study aims to determine the polarity of a plastic rod and a glass rod at contact charging with various materials. Contact charging often occurs when two electrically neutral materials are brought into contact, and then separated. Thus, selecting the types of material pairs has a critical role to make the contact charging more observable and measurable. This study was designed to address the astonishment of students who accidentally learned that a plastic rod can be positively charged at contact charging. What materials can cause the plastic rod to become positively charged at contact charging? This is the main research question of this study. Thus, we searched the polarity of a plastic rod and a glass rod at contact charging with various materials by using a typical laboratory electroscope and also a modern electronic electroscope. At the end of the study, it was shown that although the plastic rod is generally negatively charged at contact charging with many materials, it is positively charged at contact charging with a nylon garbage bag, a piece of nitric, or a piece of Teflon (PTFE). In addition, the glass rod is generally positively charged at contact charging with many materials except the human hair.

Bridge technique for hemifacial spasm with vertebral artery involvement

BackgroundTo assess efficacy and safety of a newly developed decompression technique in microvascular decompression for hemifacial spasm (HFS) with vertebral artery (VA) involvement.MethodsA rigid Teflon (Bard® PTFE Felt Pledget, USA) with the ends placed between the lower pons and the flocculus creates a free space over the root exit zone (REZ) of the facial nerve (bridge technique). The bridge technique and the conventional sling technique for VA-related neurovascular compression were compared retrospectively in 60 patients. Elapsed time for decompression, number of Teflon pieces used during the procedure, and incidences of intraoperative manipulation to the lower cranial nerves were investigated. Postoperative outcomes and complications were retrospectively compared in both techniques.ResultsThe time from recognition of the REZ to completion of the decompression maneuvers was significantly shorter, and fewer Teflon pieces were required in the bridge technique than in the sling technique. Lower cranial nerve manipulations were performed less in the bridge technique. Although statistical analyses revealed no significant differences in surgical outcomes except spasm-free at postoperative 1 month, the bridge technique is confirmed to provide spasm-free outcomes in the long-term without notable complications.ConclusionsThe bridge technique is a safe and effective decompression method for VA-involved HFS.

Comparison of Ultrasonic Methods for Detecting Defects in Unidirectional Composite Material

Non-destructive tests are of pivotal importance in the industry, as they contribute to the decreasing of maintenance costs, reducing downtime and accidents. Ultrasound is a non-destructive method that can be used with several arrangements to identify faults in engineering materials. This work evaluated the use of three ultrasonic methods applied in FRP composites to detect manufacturing defects. The critically refracted longitudinal wave (LCR), the B-Scan images, and the signal-to-noise ratio of TFM (Total Focusing Method) images were compared to detect the delamination and the fiber waviness in unidirectional composite of carbon/epoxy. Rectangular samples without defects and with defects were used in the tests. To obtain the delamination in the samples, pieces of Teflon were placed between layers and for the samples with waviness, a silica sphere was used. The results showed that LCR wave is not recommended to detect these kinds of defects, the B-Scan image is efficient in detecting delamination, and the SNR variation of TFM images allows to identify the waviness and delamination in unidirectional FRP composites.

Wedge-technique for transposition of the vertebral artery in microvascular decompression for hemifacial spasm: technical nuances and surgical outcomes.

Transposition of the vertebral artery (VA) for microvascular decompression for hemifacial spasm (HFS) is often challenging. Various procedures have been proposed to transpose the immobile tortuous VA that cannot be decompressed satisfactorily in the usual manner. A Teflon piece that is cut into a wedge shape was used for transposition of the VA as an offending artery in HFS. One or more wedge-shaped Teflon pieces were simply inserted into a small space between the VA and the brainstem or cerebellar hemisphere without any contact with the entry into the root exit zone (REZ) of the facial nerve. A minimal space can be created by slight mobilization of the VA through rostral or caudal, or in between to the lower cranial nerves (LCNs). In cases of a hypertrophic VA that is hard to mobilize, two or more rigid wedge-shaped Teflon pieces that are coated by fibrin glue can be applied to obtain adequate mobilization of the VA. Moreover, a much harder Teflon bar, which is bent into a V shape, can be used in cases of an immobile VA. Once the VA is transposed to an appropriate position, the Teflon, VA, and contacted surface of the brainstem are fixed together by drops of fibrin glue. The offending arteries were VA-posterior inferior cerebellar artery (PICA) in eight cases, VA in four cases, PICA in four cases, VA-anterior inferior cerebellar artery (AICA) in one case, and AICA in one case. Eighteen cases of HFS were successfully treated using the "Wedge technique." Symptoms disappeared within 2weeks in all patients. Transient facial nerve palsy developed in one case, and transient hoarseness developed in one case. The wedge technique is a simple straight-line maneuver that facilitates sufficient transposition of the VA without any related complications. This technique is also useful for other large offending vessels, such as the anterior or posterior inferior cerebellar arteries, which are hard to mobilize due to the torque of the vessels.

Microvascular Decompression for Glossopharyngeal Neuralgia: Clinical Analyses of 30 Cases.

ObjectiveWe present our experience of microvascular decompression (MVD) for glossopharyngeal neuralgia (GPN) and evaluate the postoperative outcomes in accordance with four different operative techniques during MVD.MethodsIn total, 30 patients with intractable primary typical GPN who underwent MVD without rhizotomy and were followed for more than 2 years were included in the analysis. Each MVD was performed using one of four different surgical techniques: interposition of Teflon pieces, transposition of offending vessels using Teflon pieces, transposition of offending vessels using a fibrin-glue-coated Teflon sling, and removal of offending veins.ResultsThe posterior inferior cerebellar artery was responsible for neurovascular compression in 27 of 30 (90%) patients, either by itself or in combination with other vessels. The location of compression on the glossopharyngeal nerve varied; the root entry zone (REZ) only (63.3%) was most common, followed by both the REZ and distal portion (26.7%) and the distal portion alone (10.0%). In terms of detailed surgical techniques during MVD, the offending vessels were transposed in 24 (80%) patients, either using additional insulation, offered by Teflon pieces (15 patients), or using a fibrin glue-coated Teflon sling (9 patients). Simple insertion of Teflon pieces and removal of a small vein were also performed in five and one patient, respectively. During the 2 years following MVD, 29 of 30 (96.7%) patients were asymptomatic or experienced only occasional pain that did not require medication. Temporary hemodynamic instability occurred in two patients during MVD, and seven patients experienced transient postoperative complications. Neither persistent morbidity nor mortality was reported.ConclusionThis study demonstrates that MVD without rhizotomy is a safe and effective treatment option for GPN.

Laparoscopic Repair of Congenital Diaphragmatic Hernia in Adults

Background, Aims, and Objectives. Congenital diaphragmatic hernia typically presents in childhood but in adults is extremely rare entity. Surgery is indicated for symptomatic and asymptomatic patients who are fit for surgery. It can be done by laparotomy, thoracotomy, thoracoscopy, or laparoscopy. With the advent of minimal access techniques, the open surgical repair for this hernia has decreased and results are comparable with early recovery and less hospital stay. The aim of this study is to establish that laparoscopic repair of congenital diaphragmatic hernia is a safe and effective modality of surgical treatment. Materials and Methods. A retrospective study of laparoscopic diaphragmatic hernia repair done during May 2011 to Oct 2014. Total n = 13 (M/F: 11/2) cases of confirmed diaphragmatic hernia on CT scan, 4 cases Bochdalek hernia (BH), 8 cases of left eventration of the diaphragm (ED), and one case of right-sided eventration of the diaphragm (ED) were included in the study. Largest defect found on the left side was 15 × 6 cm and on the right side it was 15 × 8 cm. Stomach, small intestine, transverse colon, and omentum were contents in the hernial sac. The contents were reduced with harmonic scalpel and thin sacs were usually excised. The eventration was plicated and hernial orifices were repaired with interrupted horizontal mattress sutures buttressed by Teflon pieces. A composite mesh was fixed with nonabsorbable tackers. All patients had good postoperative recovery and went home early with normal follow-up and were followed up for 2 years. Conclusion. The laparoscopic repair is a safe and effective modality of surgical treatment for congenital diaphragmatic hernia in experienced hands.

Interface fracture toughness of a multi-directional woven composite

The aim of this investigation is to measure the interface fracture toughness of a woven composite. For this purpose, double cantilever beam (DCB) specimens are tested to measure the load as the delamination grows. The specimen is composed of 15 layers of a carbon–epoxy, balanced weave with alternate layers containing fibers in the $$0^{\circ }\!/90^{\circ }$$ directions and the $$+45^{\circ }\!/\!\!-\!45^{\circ }$$ directions. A thin piece of Teflon is placed between two layers of differing directions. The specimens are analyzed by means of the finite element method and an interaction energy or $$M$$ -integral to determine the stress intensity factors, interface energy release rate and phase angles. The first term of the asymptotic solution for the stress and displacement fields obtained by means of the Stroh and Lekhnitskii formalisms is used to define auxiliary solutions for the $$M$$ -integral. The critical interface energy release rate is found and exhibits a slowly increasing resistance curve. Comparisons are made to a simple expression from the literature.

Contact De-electrification of Electrostatically Charged Polymers

The contact electrification of insulating organic polymers is still incompletely understood, in part because multiple fundamental mechanisms may contribute to the movement of charge. This study describes a mechanism previously unreported in the context of contact electrification: that is, "contact de-electrification", a process in which polymers charged to the same polarity discharge on contact. Both positively charged polymeric beads, e.g., polyamide 6/6 (Nylon) and polyoxymethylene (Delrin), and negatively charged polymeric beads, e.g., polytetrafluoroethylene (Teflon) and polyamide-imide (Torlon), discharge when the like-charged beads are brought into contact. The beads (both with charges of ∼±20 μC/m(2), or ∼100 charges/μm(2)) discharge on contact regardless of whether they are made of the same material, or of different materials. Discharge is rapid: discharge of flat slabs of like-charged Nylon and Teflon pieces is completed on a single contact (∼3 s). The charge lost from the polymers during contact de-electrification transfers onto molecules of gas in the atmosphere. When like-charged polymers are brought into contact, the increase in electric field at the point of contact exceeds the dielectric breakdown strength of the atmosphere and ionizes molecules of the gas; this ionization thus leads to discharge of the polymers. The detection (using a Faraday cup) of charges transferred to the cup by the ionized gas is compatible with the mechanism. Contact de-electrification occurs for different polymers and in atmospheres with different values of dielectric breakdown strength (helium, argon, oxygen, carbon dioxide, nitrogen, and sulfur hexafluoride): the mechanism thus appears to be general.

Microvascular decompression of the optic chiasm

Elongation of the anterior cerebral artery (ACA) and subsequent compression of the chiasm rarely have been reported as causes of a visual field deficit. Neither has microvascular decompression of the chiasm been described in this circumstance. The authors report on a case of progressive visual deficits caused by compression of the optic apparatus by a right elongated ACA as documented on MR imaging. Microvascular decompression was proposed as treatment. The right A(1) segment was larger than usual and tortuous, transmitting its pulsations into the chiasm. A piece of Teflon was inserted between the A(1) segment and the chiasm. Following surgery, the visual field deficit progressively improved. At 4 months after surgery, the patient's visual fields were normal. Therefore, an elongated ACA can compress the chiasm and result in a visual field deficit. In such circumstances when facing a progressive visual field deficit, microvascular decompression may improve vision.

Ectopic choroid plexus associated with trigeminal neuralgia: case report

A 55-year-old man underwent a microvascular decompression procedure for a pharmacoresistant trigeminal neuralgia. Preoperative MRI showed a neurovascular conflict between the Vth nerve root and the superior cerebellar artery. Dissection of the intracisternal trigeminal root was undertaken, and a piece of Teflon was positioned between the artery and the nerve. Choroid plexus was found squeezing the root entry zone of the Vth nerve and partially removed. The patient did not improve after the vascular decompression procedure. Trigeminal neuralgia could be due to a mechanical irritation of the intracisternal nerve root. Since vascular decompression of the trigeminal root did not relieve the pain, we suggest that the presence of choroid plexus at the root entry zone of the nerve may have induced trigeminal neuralgia in this patient.

Impurity effects on the band structure of one-dimensional photonic crystals: experiment and theory

We study the effects of single impurities on the transmission in microwave realizations of the photonic Kronig–Penney model, consisting of arrays of Teflon pieces alternating with air spacings in a microwave guide. As only the first propagating mode is considered, the system is essentially one-dimensional (1D) obeying the Helmholtz equation. We derive analytical closed form expressions from which the band structure, frequency of defect modes and band profiles can be determined. These agree very well with experimental data for all types of single defects considered (e.g. interstitial and substitutional) and show that our experimental set-up serves to explore some of the phenomena occurring in more sophisticated experiments. Conversely, based on the understanding provided by our formulae, information about the unknown impurity can be determined by simply observing certain features in the experimental data for the transmission. Further, our results are directly applicable to the closely related quantum 1D Kronig–Penney model.

Neurovascular Compression Syndromes

Neurovascular compression syndromes are a group of pathological conditions caused by vascular compression of cranial nerves in the cerebellopontine angle. These syndromes include trigeminal neuralgia, hemifacial spasm, disabling positional vertigo, tinnitus, and glossopharyngeal neuralgia. Historical Background: In 1773, Fothergill gave a clear description of trigeminal neuralgia while in 1888 Gowers described hemifacial spasm as a disease entity. In the 1930s Dandy first observed abnormal contacts between vessels and the trigeminal nerve in patients suffering from trigeminal neuralgia. In the 1940s, Sunderland observed abnormal neurovascular relationships in the brains of elderly cadavers. In the 1960s Gardner performed vascular decompression in patients with hemifacial spasm and trigeminal neuralgia. In the 1970s and in the 1980s, Jannetta and Moller greatly contributed to clarifying the concept of neurovascular compression and to developing definitive microsurgical procedures aimed at treating these symptoms. Surgery: Microvascular decompression is a surgical procedure used to separate the offending vessel(s) from the affected cranial nerve. Usually, a piece of Teflon is placed between the blood vessel and the nerve to prevent recontact. Treatment of vascular compression syndromes by microvascular decompression is effective with a consistently high cure rate. In Parma and in Marseille the decompression was performed via a minimally invasive retrosigmoid approach in the majority of cases. The use of the endoscope (Magnan, 1993) allows a safe and reliable identification of the offending vessel(s) and confirms the correct position of Teflon before closure. The enlarged middle cranial fossa approach was used in Parma to treat hemifacial spasm. A chemical product called mesna facilitates elevation of the compressing vascular loop from the affected cranial nerve. To perform the so-called “chemically assisted dissection” (CADISS®) we use the common mechanical instruments opportunely modified in order to deliver the mesna solution on the tip of the instruments and, therefore, directly in contact with the tissues to be detached, thus reducing its inappropriate diffusion. The authors will present the surgical technique of microvascular decompression and the results obtained in 500 decompression procedures.

ELECTRETS TO MEASURE ION CONCENTRATION IN AIR

Positive and negative ions are produced in air, mainly due to radon and terrestrial/cosmic radiation sources. Measuring ion concentration in air indirectly provides a measure of these sources. Electrets (electrically charged pieces of Teflon), when exposed in the environment, collect ions of opposite sign leading to a measurable decrease in charge, depending upon the exposure time and ion concentration. This work describes a method of correlating electret discharge rate to the ion concentration as measured by a calibrated ion density meter. Once calibrated, electrets can then be used to measure ion concentration of either sign. The ion concentration in ambient air was measured to be about 200 ions mL(-1), measured over several hours. Both positive and negative ion concentrations were similar. In a typical room, negative ion concentration was about 3,500 ions mL(-1), and, surprisingly, there were no positive ions at all in that room. Being an integrating passive device, the method provides the unique possibility of measuring low or high concentrations of positive or negative ions over extended periods, which is difficult to do with other ion concentration measuring instruments.

Experimental Dentin-Based Approaches to Tissue Regeneration in Vital Pulp Therapy

The potential direct induction of odontoblastlike cell differentiation at the surface of implanted dentin matrix has been tested in a series of capping experiments. Pieces of Teflon (control) or autogenous dentin matrix were placed in contact with the wound surface at a conventional capping situation, or at the dentinal base of the cavity at a distance from the exposed pulp periphery. Tissue responses were studied by light microscopy after periods of 2 and 4 weeks. Partial degradation of the dentin matrix implants was seen. Formation of atubular calcified matrix, occasionally followed by tubular reparative dentin, was consistently detected in association with dentinal particles. The area between the traumatized dental pulp periphery and the capping material had been occupied by a well-vascularized tissue, regardless of the capping material and postoperative time period. Traces of calcified matrix were detected along the cut dentinal walls. The present data indicate that dentin matrix is limited in its ability to directly induce odontoblastlike cell differentiation and reparative dentin formation at the surface of mechanically exposed pulp of mature teeth. Furthermore, it seems that the traumatized mature pulp maintains the ability to grow, while a calcifying potential could be expressed by this growing part of the pulp core.

Descompresión microvascular de la neuralgia del trigémino causado por dolicoectasia vertebrobasilar

Trigeminal neuralgia due to vertebrobasilar dolichoectasia is an acquired disease whose true incidence is not known. Microvascular decompression is the most effective technique both for symptomatic relief and for the conservation of nerve structure and function, in spite of the potential complications of all major surgery. In cases which are drug-resistant and have a life expectancy of over five years, microvascular decompression may be done using several techniques. We present three cases with drug-resistant trigeminal neuralgia. One patient had a history of previous cerebrovascular ischaemia, another had arterial and pulmonary hypertension. In all cases vertebrobasilar dolichoectasia was seen on magnetic resonance. Microvascular decompression of the trigeminal nerve was done, placing pieces of Teflon between the tentorium and the artery to displace it. Postoperatively the pain disappeared in two cases and was much relieved in the other, making good progress with no complications. Trigeminal neuralgia due to vertebrobasilar dolichoectasia is a progressive acquired disease. The imaging technique of choice is magnetic resonance. Cerebral angiography may be useful for confirmation. This new technique of microvascular decompression avoids excessive manipulation of the ectatic, arteriosclerotic basilar artery and also pulsatile compression, so that the risk of secondary effects is reduced and the efficacy of the decompression maintained. Further cases are needed to confirm the usefulness of this technique.

Time-Resolved Resonance Raman Spectroscopy Using a Fast Mixing Device

A new fast mixing device has been developed. Our attention has been paid to improving the apparatus design in order to decrease the mixing dead time and to enhance the mixing efficiency. We modified and, mainly, simplified the system proposed by Clegg. The new device comprises two concentric tubes and a platinum spherical ball with a single piece of Teflon used as a support housing. Mixing is thus performed by the induced turbulent flow which can be generated by forcing a liquid stream to flow through channels between a Pt ball and a glass wall. This device offers many advantages relative to conventional mixing devices. The 99% mixing time for the device has been found to be 30 - 80 μs, which is at least a factor of 10 faster than the older devices. This technique can be applied using any type of fast reaction, solvent or laser. The stability of the stream and the excellent reproducibility allow measurements of the rate constants of very fast reactions.

Tangential intracortical pathways and the development of iso-orientation bands in cat striate cortex

Evidence is accumulating that tangential connections are a prominent feature of cortical organization. In the mammalian visual cortex, these connections appear to be related to columnar systems and theoretical considerations have suggested that they contribute to the development of regularly spaced orientation columns. We tested this assumption and examined whether early c cortical lesions affected the formation and layout of the pattern of iso-orientation bands. In the striate cortex of 2-week-old kittens, tangential fiber paths were disrupted unilaterally along the representation of the horizontal meridian either by cuts, or by suction or by implanting pieces of Teflon. At this age, tangential fibers are still growing, orientation selectivity is only poorly developed and 2-deoxyglucose mapping does not yet reveal orientation columns. When the kittens were 7–10 weeks old, the organization of orientation bands was studied with the 2-deoxyglucose technique in flat-mounts of both visual cortices. In addition, kittens from the same litters as the experimental animals, having received the same lesions at the same postnatal day were subjected to neuroanatomical experiments to assess the effect of the lesion on the tangential fibers. These investigations revealed that a small fraction of tangential fibers had grown across the lesion when no mechanical barrier was implanted while disruption of tangential connections was complete in cases who had received Teflon implants. Apart from minor irregularities that were confined to the vicinity of the lesion, the 2-deoxyglucose experiments showed no differences in the pattern of orientation bands between the lesioned and intact hemispheres. In both, the bands extended throughout all cortical layers and their main trajectories were orthogonal to the representation of the vertical meridian. We conclude that at least from two weeks of age onwards, intracortical tangential connections are not necessary for the development of the regular pattern of iso-orientation bands in the striate cortex of cats.

Thin-layer hydrodynamic biamperometric end-point detection: application to the coulometric titration of arsenic(III) with bromine

A sandwich-type thin-layer cell has been applied to hydrodynamic biamperometric end-point detection in coulometric titrations. The detector cell, constructed from two pieces of teflon, has platinum indicator electrodes and is placed in a flow loop attached to the coulometric titration cell. The thin-layer cavity has a volume of 6.5 μl and a thickness of 51μm, which are obtained using teflon tape as a spacer. A peristaltic pump maintains a continual flow through the loop. The titration cell is a closed vessel completely filled with the solution to be titrated. Operational amplifier circuits control the potential difference applied across the two thin-layer electrodes, and to measure the current developed in the thin-layer cell. Noise arising from the pulsed nature of the flow is reduced by a factor of 25 by using an electronic filter. The titration of arsenic(III) with electrogenerated bromine was used to study the performance of the system. Concentrations from 24 ppb to 1.6 ppm can be determined with relative inaccuracies of +4 and +0.1%, respectively.

The forehead flap: a modification in technique.

The use of the forehead flap for reconstruction within the oral cavity after tumour resection is discussed. A minor modification in technique is described. The sub-zygomatic route to the oral cavity is used and a piece of teflon or sialalastic sheet is sewn over the raw surfaces of the flap which lies within the tunnel in the cheek to facilitate retrieval of the pedicle.