Tube Protrusion Research Articles

Surgical treatment of Ahmed glaucoma valve’s tube protrusion relapse. Clinical observations

In the practice of an ophthalmic surgeon, patients with a large number of concomitant conditions after repeated surgical interventions are seen with increasingly frequency. One of the grave complications in such patients is secondary glaucoma with a refractory type of course. After successful compensation of intraocular pressure in such patients, the risk of complications increases many times, for example, protrusion of the Ahmed valve drainage tube, which becomes the entrance gate for infection, which can lead to endophthalmitis. This article presents clinical cases of surgical treatment of recurrent protrusion of the Ahmed valve drainage tube.

Friction stir welding of carbon black reinforced high-density polyethylene tube-to-tubesheet joints

Industrial heat exchanger applications dealing with highly corrosive fluids demand the use of thermoplastic heat exchangers because of the chemically inert and anti-fouling nature of the thermoplastics. A non-conventional joining framework, based on the friction stir welding (FSW) technique, is used to form high-quality thermoplastic tube-to-tubesheet joints (TTJs). The proposed technique has potential applications for thermoplastic shell-and-tube heat exchangers and piping industries (as flange-to-pipe joints). In this work, the tube and tubesheet materials made of carbon black reinforced high-density polyethylene were used. The effect of different FSW parameters (rotational speed, plunge depth, tube protrusion, dwell time) on the tube pull-out behavior was investigated. The FSW technique showed capabilities at a wide range of operating conditions. The highest load bearing capacity of 517 N was achieved using the FSW process, much higher than adhesive joints. Also, it provides higher extensions at maximum load than adhesive joints, with the highest extension of 5.161 mm. Two FSW cases provided high leak paths of 77% and 58% remaining sheet thickness (greater than tube thickness) along with high load bearing capacity and corresponding extensions. The macroscopic and SEM-based fractographic studies illustrated three types of failure behavior: ductile, brittle, or mixed depending on the FSW process conditions. The DSC results showed no significant crystallinity changes in the weld material. The TGA results showed no significant thermal degradation occurring in the weld material. Further, the FTIR analysis indicated possible oxidation of the weld material. The capability to form TTJs with high leak path, high load bearing capacity, and no significant material degradations makes the FSW technique suitable for thermoplastic shell-and-tube heat exchanger applications.

Performance of flow distribution in a microchannel parallel flow gas cooler with stepped protrusion depth header

Abstract Microchannel parallel flow gas cooler is commonly used in transcritical carbon dioxide automotive air conditioning system. To investigate the influence of the flat tube protrusion depth on fluid distribution, a numerical calculation model of microchannel parallel flow gas cooler with D-shaped header is established. With the object of even flow distribution, a novel stepped protrusion depth header is proposed. The effects of new header on the flow distribution of gas cooler were studied by numerical simulation. The results show that the flow distribution performance of gas cooler can be improved by changing the flat tube protrusion depth. Changing the protrusion depth of three groups of flat tubes simultaneously can achieve a better flow distribution performance of gas cooler than changing the protrusion depth of only one or two groups of flat tubes. When compared with the protrusion depth of all flat tubes is 0, the novel stepped protrusion depth header reduces the total flow distribution nonuniformity of gas cooler by 34–51%. The research in this paper provides a method for improving the flow distribution performance of gas coolers.

Two-phase refrigerant distribution in a two-row/six-pass mini-channel aluminum evaporator

ABSTRACT R-134a distribution in an evaporator having two-row/six-pass configuration was experimentally studied with the inlet quality 0.2 and the outlet superheat 5°C. The mass flux was varied from 63 kg/m2s to 117 kg/m2s. The flow distribution generally followed the expected trend. The insert configuration (multi-hole or a single rectangular hole) affected only nearly passes. Furthermore, better liquid distribution was obtained for the single rectangular hole insert. The effect of tube protrusion depth was only significant at the first pass. As a result, flow distribution correlations obtained from the two-row/four-pass configuration predicted the two-row/six-pass configuration data reasonably well.

Dacryocystectomy with Lacrimal Silicone Intubation in Challenging Patients Affected by Recurrent Dacryocystitis and Epiphora: Expanding Minimally Invasive Approach Indications

Objective:In this study, we evaluated the feasibility and safety of dacryocystectomy associated with lacrimal intubation, for the treatment of recurrent dacryocystitis and epiphora secondary to lacrimal obstruction with compromised lacrimal sac, was evaluated.Subjects and Methods:32 patients underwent dacryocystectomy with Crawford tubes canalicular insertion, performed by a single surgeon. Post-operative visits were scheduled at 1stand 10th day, 1, 3, and 6 months. At each follow-up visit, the prevalence of epiphora and dacryocystitis was evaluated and compared with baseline data. Also, we evaluated the prevalence of local and systemic post-operative adverse events during the follow-up period.Results:11 patients (34.38%) reported persistent epiphora, which lasted for 30 days after surgery. Among them, 9 subjects (28.13%) complained occasional epiphora even at the six months follow-up. In the event of dacryocystitis or subacute phlogosis before surgery, patients reported a definitive symptom resolution. Other reported adverse events were epithelial corneal erosion due to Crawford tube protrusion (4 cases, 12.5%), a Crawford tube extrusion case (3.13%), 3 cases of surgical wound dehiscence (9.36%), and a case of mild local bleeding persisting for 15 daysConclusion:A significative epiphora reduction was observed after surgery with an acceptable safety profile, expanding dacryocystectomy indications. This procedure provides a satisfactory resolution of recurrent dacryocystitis. However, this approach should be performed only in well-selected cases: elderly/frail patients with altered lacrimal sacs, epiphora associated with recurrent infections, and failure after dacryocystectomy.

1870 Chest Tube Protrusion Into the Gastric Cavity Resulting in Biliary Drainage

INTRODUCTION: Biliary drainage through a chest tube is a rare clinical finding that might be caused by Biliothorax or inadvertent penetration of the chest tube to the esophagus or the proximal stomach wall. We present a 63-year-old male patient who underwent Ivor Lewis esophagogastrectomy with his post procedural course complicated by chest tube migration and protrusion into the stomach cavity through gastropleural fistula. CASE DESCRIPTION/METHODS: A 63-year-old male patient who underwent Ivor Lewis esophagogastrectomy for distal esophageal adenocarcinoma, his clinical course was complicated by left sided pleural effusion and pneumothorax for which a chest tube was inserted. The patient clinical condition was stabilized and was discharged to an inpatient rehabilitation facility with the chest tube. Twenty days after discharge, the patient started to have bilious drainage through his chest tube again. He was admitted to hospital, imaging showed recurrent left pleural effusion. EGD was performed and showed chest tube protrusion into the stomach cavity through a gastropleural fistulas near the gastroesophageal junction. The chest tube was retracted and the gastropleural fistula was closed with over-the-scope clips. Bilious output stopped and the chest tube was removed with no further leakage. DISCUSSION: Biliary drainage through a chest tube is a rare clinical entity. It is highly suggestive of an esophageal leakage from a procedural complication. Gastropleural fistulae are rare and often occur as a complication of gastroesophageal surgery. When present, hardware, such as a chest tube, can be trapped into them resulting in various presentations. Endoscopic closure with over-the-scope clips may represent an effective and less invasive technique to close post procedural fistula tracts.

Characterization of two-phase flow distribution in microchannel heat exchanger header for air-conditioning system

The two-phase flow distribution behavior of R410A within the vertical header of a microchannel heat exchanger with multiple horizontally oriented microchannel flat tubes was investigated and is reported in this paper. Unlike most previous studies, which examined the distribution at lower flowrates applicable mostly to automobile applications, this work evaluated higher flowrates relevant to actual air conditioning evaporator applications with larger size headers. The following operating conditions, were utilized: an inlet mass flowrate that varied from 40 to 200 kg h−1 (mass flux of 27–250 kg m−2 s−1 in the header), vapor qualities of 0.1, 0.2, and 0.6, and evaporating temperatures of 10 and 15 °C. The tube protrusion depth into the header was set at 0 and 50%. Flow distribution profiles derived from the experiment measurements and clear visualization images captured by a high speed camera showed that the distribution improves for increased inlet mass flux at low vapor quality, while a 5 °C difference in evaporating temperature does not yield a substantial distribution change. A 50% protrusion produces higher inertial forces pushing the liquid level towards the top section. A correlation was developed to predict the liquid distribution by relating the portion of liquid exiting the branch tube to the liquid at the immediate header as a function of the liquid Froude number.

Dacryocystorhinostomy for Acquired Nasolacrimal Duct Stenosis in the Elderly (≥80 Years of Age)

The incidence of acquired nasolacrimal duct obstruction (NLDO) increases with age. Dacryocystorhinostomy, the definitive treatment for NLDO, has a high success rate (80%-100%) with a low complication rate (1%-6%), but surgical outcomes have not been reported previously specifically for an elderly population, in which there may be increased risk for intraoperative and postoperative complications. The purpose of this study was to examine surgical outcomes and complication rates of dacryocystorhinostomy in an elderly population. Retrospective cohort study. Patients 80 years of age or older undergoing external dacryocystorhinostomy at the Mayo Clinic between January 1, 1990, and December 31, 2010, were compared with a matched control group of younger patients (40-79 years of age) undergoing external dacryocystorhinostomy by the same surgeons. We reviewed the medical charts for patients as described above. Data abstracted from patient medical records included symptomatic relief and complications such as tube protrusion, infection, persistent bleeding, and return to operating room. Statistical analysis included a 2-sample t test to compare continuous variables, chi-square testing for categorical comparisons, and the generalized estimating equation model to control for nonindependence. Primary end point was symptomatic improvement at last follow-up. Secondary end points included anatomic patency, adverse event rate, and return to operating room within 1 month of surgery. Forty-two dacryocystorhinostomies (32 patients) were performed in the elderly group. The control group comprised 73 dacryocystorhinostomies in 63 patients. Resolution of symptom rate at last follow-up was 64% in the elderly group versus 86% in the younger cohort (P= 0.02). Although there was no difference between groups with respect to common postoperative complications, there was a higher rate of predefined serious complications in the elderly group (5 events vs. 1 event; P= 0.01). There was no difference between groups regarding need for additional eyelid surgery (P= 0.30). Although most elderly patients experience symptom resolution after dacryocystorhinostomy, the rate of symptom resolution was lower than that of younger patients. The risk of routine complications was similar between the groups. The risk of serious complications was higher in the elderly group.

An investigation of the effects of geometry design on refrigerant flow mal-distribution in parallel flow condenser using a hybrid method of finite element approach and CFD simulation

Flow mal-distribution in tubes is an important problem in parallel flow heat exchangers (PFHXs) which should be considered in heat exchanger modeling. In the present study, a hybrid method is developed for flow distribution forecasting based on simultaneous use of computational fluid dynamics (CFD) simulation for 3D analysis of flow in PFHX headers and finite element model for solving flow within tubes. The developed method forecasts are verified against the experimental data of a parallel flow condenser (PFC) performance. The method is then utilized to investigate the effects of tube protrusion depth, inlet tube location, inlet tube diameter and combination of tube protrusion depth and inlet tube location on refrigerant flow mal-distribution. The data indicate flow mal-distribution increment (increase of standard deviation (STD) from 0.51% to 1.77%) by increasing the tube protrusion depth from 1/4 to 3/4 of header diameter which results in about 14% increment in pressure drop and 3.9% decrement in capacity. Also, reduction of flow mal-distribution in cases of increasing the inlet tube diameter and locating the header inlet on the top of the header, a small distance away from the first tube is observed. The presented model and results can be used to accurately design PFCs.

Phase split in parallel vertical channels in presence of a variable depth protrusion header

The air and water flow distribution are experimentally studied in a test section simulating a heat exchanger composed by a round header and 16 parallel upward channels. The effects of the tube protrusion depth as well as the gas and liquid superficial velocities are investigated and the results are compared with previous data. A new fitting solution to be inserted in the header has been developed based on previous findings by the Authors. The fitting geometry belongs to the family of the protruding pipes but the protruding depth has been varied along the header in order to cope with expected liquid and gas mass flow rates in the parallel channels. The flow at the header inlet is intermittent and annular and water and air have been employed as two phase mixture. The new header fitting demonstrated to yield meaningful improvements in phase distribution in terms of either dimensionless liquid and gas flow ratios or standard deviation of phase flow ratio (the overall performance parameter STD2 here presented decreased by 64%) when compared to the previous configurations.

Nazolakrimal kanal obstrüksiyonunun tedavisinde endonazal dakriyosistorinostomi (DSR) ve endokanaliküler diyot lazer DSR'nin karşılaştırması

Objective: Dacryocystorhinostomy (DCR), the treatment for nasolacrimal duct obstruction, is generally performed endonasally. In this retrospective study, we compared the anatomical and functional success rate of endonasal DCR with endocanalicular diode laser DCR. Methods: Medical records of 53 patients in endonasal DCR group (Group 1) and 47 in endocanalicular diode laser DCR group (Group 2) were analyzed for preoperative syringing and probing evaluations as well as surgical details, outcomes and complications. Results: Recurrence was observed in eight patients in Group 1 and six in Group 2. Although the recurrence rates differed between the two groups, this difference was not statistically significant (p>0.05). The complications in Group 1 included eight cases of synechia and one tube protrusion, whereas the complications in Group 2 included two cases of synechia, two tube protrusions and two punctum atrophies. The presence of allergy, concha hypertrophy and septum deviation did not significantly increase the rates of recurrence or complications (p>0.05). Bleeding and pain were observed significantly more frequently in Group 1 and the patient comfort was significantly better in Group 2 (p

Single-phase and two-phase flow pressure drop in the vertical header of microchannel heat exchanger

Refrigerant maldistribution among parallel microchannel tubes deteriorates the performance of microchannel heat exchanger because it creates unwanted superheated region that has lower heat transfer. Besides phase separation in the header, the pressure drop in the header causes the pressure drop in the microchannel tube to be different between each tube, also resulting in flow rate maldistribution. This paper experimentally investigates the pressure drop of single-phase and two-phase flow in the vertical header of a multi-pass microchannel heat exchanger. The overall pressure drop in the header includes four components: acceleration, gravitation, friction, and minor pressure drop due to microchannel tube protrusion. The gravitation and minor pressure drops are dominant for single-phase liquid flow and at low qualities of two-phase flow, whereas the acceleration and minor pressure drops are dominant for single-phase vapor flow and at high qualities of two-phase flow. The model to predict the overall pressure drop in the header for single-phase and two-phase flow is proposed based on the experimental results.

One-stitch anastomosis through the skin with bicanalicular silicone tube intubation for treatment of superior and inferior canalicular lacerations

Objective To evaluate the efficacy of one-stitch anastomosis through the skin with bicanalicular silicone tube intubation to treat the bicanalicular lacerations.Methods Retrospectively,11 consecutive patients with both superior and inferior canalicular lacerations in one eye who underwent surgical repair using one-stitch anastomosis through the skin and bicanalicular stent were included.All the operations were performed under surgical microscope,5-0 silk sutures were used and bicanalicular silicone tubes (the diameter was 0.8 mm) were intubated,with one lacerated canalicula one-stich anastomosis through the skin.The stents were left in the place for 3 months postoperatively and then were removed.The follow-up period was 3 ～36 months(average 14 months).Results In 11 patients,9 patients were cured entirely,1 patient were meliorated,1 patient had no effects.All the patients had got good recovery of eyelid laceration without traumatic deformity in eyelid or canthus.There was no early tube protrusion or punctal slits in the patients.Conclusion One-stitch anastomosis through the skin with bicanalicular silicone tube intubation is a good method in repair of bicanalicular laceration in one eye.The cut ends could be anastomosed directly.No suture remained in the wound permanently.There was no suture-related granuloma which might cause obstruction or stenosis of canaliculi. Key words: Laceration, canalicular, superior and inferior; Repair; Anastomosis, through the skin, one stitch; Intubation, bicanalicular

Design method of flow distribution in nuclear reactor systems

Flow distribution is encountered widely in nuclear reactor systems including distribution of liquid coolant, feedwater or steam sparger, and high energy fluid into condenser of steam turbine. Distributors with parallel ports or openings are common designs which may be very sensitive to variations of structure and dimensions of a manifold and its ports. Non-uniformity of flow distributions causes largely potential malfunction and poor efficiency, even failures. In this paper, a theoretical model was developed for a tapered distributor. Analytical solutions were obtained for evaluation of influence of operating conditions and structures and dimensions of distributor and ports on flow distributions. Structural parameters were identified and hydraulic characteristics were analysed. The orifices, slope and tube protrusion are useful for improvement of the flow distributions. The uniformity of the flow distributions can be improved about 10–60% by fitting orifice rings or tube protrution with a range of the minor loss coefficients: 0.5–3. Finally design criteria were suggested for industrial applications. This provides a simple and easy-to-use tool for design of the flow distribution in nuclear reactors and power boilers.

EFFECT OF INLET CONFIGURATION ON DISTRIBUTION OF AIR–WATER UPWARD FLOW IN A HEADER OF A PARALLEL FLOW HEAT EXCHANGER

The effect of inlet configuration (parallel, normal, vertical) on flow distribution in a parallel flow heat exchanger consisting of round headers and ten flat tubes is experimentally studied using air and water. The effects of tube protrusion depth as well as header mass flux, and quality are investigated for upward flow configuration. It is shown that best flow distribution is obtained for vertical inlet configuration, followed by normal inlet and parallel inlet configuration. For upward flow, significant portion of the water flows through the rear part of the header. As protrusion depth increases, more water is forced to the rear part of the header. The effect is most significant for parallel inlet, followed by normal and vertical inlet. The effect of mass flux or quality is opposite to that of the protrusion depth. Possible explanation is provided from flow visualization results.

Effectiveness of canalicular laceration repair using monocanalicular intubation with Monoka tubes

This study aimed to evaluate the clinical efficacy of canalicular laceration repair using monocanalicular intubation with Monoka tubes. A total of 36 single lacerated canaliculi were repaired using monocanalicular intubation with Monoka tubes, without mucosal anastomosis of the canaliculi, and were retrospectively reviewed. Demographic information, injury locations, associated ocular injuries, complications and outcomes were analysed. Mean patient age was 34 years (range 1-64 years). Tubes were removed at a mean of 4.2 months (range 3-6 months). There were 26 lower canalicular lacerations (72%) and 10 upper canalicular lacerations (28%). Overall, 34 of 36 cases (92%) showed improvement in symptoms and exhibited positivity on the dye disappearance test at 4-12 months after the procedure (mean 7.8 months). In total, 21 patients (58%) achieved complete success, 13 patients (36%) achieved partial success and two patients (6%) suffered surgical failure. Complications were seen in five cases and included two early tube protrusions, two punctal slits and one punctal granuloma. Monocanalicular intubation with Monoka tubes leads to successful outcomes without significant complications and offers an alternative to bicanalicular intubation in the treatment of monocanalicular lacerations.

Distribution of air–water annular flow in a header of a parallel flow heat exchanger

The air and water flow distribution are experimentally studied for a heat exchanger composed of round headers and 10 flat tubes. The effects of tube protrusion depth as well as header mass flux, and quality are investigated, and the results are compared with previous 30 channel data. The flow at the header inlet is annular. For the downward flow configuration, water flow distribution is significantly affected by tube protrusion depth. For flush-mounted geometry, significant portion of water flows through frontal part of the header. As the protrusion depth increases, more water is forced to rear part of the header. The effect of header mass flux or quality is qualitatively the same as that of the protrusion depth. For the upward flow configuration, however, significant portion of water flows through rear part of the header. The effect of protrusion depth is the same as that of the downward flow. However, the effect of header mass flux or quality is opposite to the downward flow case. Compared with the previous 30 channel configuration, the present 10 channel configuration yields better flow distribution. Possible explanation is provided from flow visualization results.

A remark on helical waveguides

Motivated by a proposal to create an optical helix-shaped waveguides for cold atoms and molecules, we discuss local perturbations which can create bound states in such a setting. This is known about a local slowdown of the twist; we show that a similar effect can result from a local tube protrusion or a change of the helix radius in correlation with its pitch angle.

Shortening multiwalled carbon nanotube on atomic force microscope tip: Experiments and two possible mechanisms

We demonstrate a technique to cut a multiwalled carbon nanotube (MWNT) attached on an atomic force microscope tip by flowing direct current through the nanotube as a method to precisely control nanotube tip length. The cutting process consists of two steps: (1) making a mechanical contact between a sharp metal wire and a target cutting position on a MWNT attached to a silicon mother tip, and (2) applying voltage between the MWNT and the metal wire until the current flow cuts the tube. To cut the MWNT without discharging, a firm mechanical and electrical contact was made between the tube and the wire. Nanotubes were reproducibly cut at the contact point, and we achieved a 30nm cutting resolution and a 100nm shortest tube protrusion. We simultaneously monitored the current flow through the nanotube during the cutting process and evaluated the current size of each MWNT tip at the moment of cutting. We found that the cutting process happened in two current ranges: higher than 100μA and smaller than 1μA. The mechanism of cutting at high current cutting process is attributed to unimolecular decomposition reaction, and we propose that at small current the cutting process may be done by chemical etching, which is activated by the current.

Two-phase flow distribution of air–water annular flow in a parallel flow heat exchanger

The air and water flow distribution are experimentally studied for a round header – flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is 30. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.