T-shaped Bar Research Articles

Different protocol bar designs made of polyether ether ketone (PEEK) and metal: an analysis of mechanical behavior

Objective: To assess the flexural strength (FS) of protocol bars on implants made of polyether ether ketone (PEEK) and metal. Methods: Thirty PEEK bars and thirty metal bars (control) were manufactured in three different cross-sectional designs (n = 10): rectangular solid bar (R); T-shaped bar (T); and inverted-T shaped bar (T-inv). The 30 cm bars were screwed onto Cone Morse implants measuring 3.75 x 11.0 mm and subjected to FS test on a universal testing machine (0.5 mm/min), with load applied to the pontic. Then, the counter-torque (CTorque) was measured on the screws following the test. Results: Both the PEEK and metal bars showed the highest FS values for the R-type design, followed by the T and T-inv designs. On average, FS values of PEEK bars for the T and T-inv designs were, respectively, 32.5% and 47.2% smaller than the R-shaped bars. On metal bars, the T and T-inv designs showed values 19.9% and 30.5% smaller than that found for the R design. However, regardless of design, the Ni-Cr bars showed consistently higher FS values. CTorque was not affected by material, but the R design showed higher values. Conclusion: The bar design influences FS. Regardless of design, metal bars show higher FS relative to PEEK. On the other hand, CTorque was not affected by material; in terms of design, the R-shaped bars showed lowest CTorque and T and T-inv showed no statistical difference.

Еволюція методик хірургічної корекції лійкоподібної деформації грудної клітки в дітей: одноцентровий досвід

Pectus excavatum (PE) in children is the most common pathology among orthopedic diseases of the anterior chest wall. Today in the world the main direction of scientific research in the surgical correction of this pathology is safety during surgery for the patient and the introduction of minimally invasive techniques. Purpose – to conduct a comparative analysis of the results of thoracoplasty in children with PE using different surgical techniques to reduce trauma and duration of surgery and blood loss; to study the optimal correction results to accelerate psycho-physical adaptation after the Nuss procedure. Materials and methods. The treatment of 289 patients operated on for PE in the orthopedic and traumatology department of National Children’s Specialized Hospital «OKHMATDYT» were analyzed. According to the methods of thoracoplasty used, patients were divided into 3 groups. In the first group (n=112) PE correction was performed using Nuss operation with subxiphoid access and tactile control during the retrosternal bar placement; in the second group (n=79) Nuss procedure was performed under thoracoscopic control, where one retrosternal T-shaped bar with additional lateral stabilizer was implanted and fixed on the ribs with a resorbable suture or wire; in the third group (n=98) surgical treatment of PE was performed using the Nuss procedure under thoracoscopic control using a fixator consisting of two retrosternal bars-arches, which are interconnected by lateral bars, the «Bridge» technique. Results. When using thoracoscopic control and temporary sternum elevation by modificated «Park crane» during the correction of PE, the time of surgery and blood loss was reduced. No rotations of the fixator throughout the observation period and lower postoperative pain syndrome were observed in patients of the 3rd group, who underwent corrections with the «Bridge technique». Conclusions. The technique of minimally invasive correction of pectus excavatum (MIRPE), Nuss operation, using thoracoscopic control and temporary elevation of the sternum during pectus bar placement is a safe and effective method of thoracoplasty. The use of two plates (the «Bridge» system) during minimally invasive correction is the operation of choice for adolescent children with funnel chest deformities. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of all participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: pectus excavatum; chest deformity; Nuss operation, surgery, pediatrics, thoracoplasty, results.

Experimental investigation of a trench weir with T-shaped bars

The most common type of diversion structure used in boulder streams is a trench weir. It is a simple structure built below the bed level of streams, and the top of it is covered with bottom rack. Bottom rack consists of bars of various shapes like circular, rectangle, T-shaped, etc. It is placed over the trench weir with a desired porosity to control sediment ingestion into trench. In this present study, T-shaped bars are used because sediment ingestion and maintenance in the bottom rack consisting of T-shaped bar shall likely too low as compared to the rounded bars and rectangular bars. As in previous studies, Garcia et al. (Water 10(1035):1–21, 2018a, Water 10(1699):1–21, 2018b) compared the blocking capacity of bottom intakes having circular bars with intakes having T-shaped bars, they claimed that circular bar is inefficient as compared to T-shaped bars. The present study is based on experimental investigation of trench weir consisting of T-shaped bars under free flow condition, and it was found that the coefficient of discharge decreases with an increase in clear spacing of rack, slope of bottom rack, specific energy of approach flow, Froude number and Reynolds number. An equation is also being proposed to calculate coefficient of discharge with a maximum error of ± 20%.

Occlusion in Bottom Intakes with Circular Bars by Flow with Gravel-Sized Sediment. An Experimental Study

Obstruction of the racks in bottom intakes due to sediment wedged in the slit of the bars can significantly reduce diverted flow. Notwithstanding the design recommendations that are found in the literature, the problem of rack occlusion continues to occur in built structures. This work focuses on the clogging effects in the circular bars of a bottom rack system using gravels whose median diameter, d50, is close to the spacing between the bars. An experimental campaign including 24 tests, each repeated time times, with six different longitudinal slopes from 0 to 35% and four different specific incoming flow rates, q1, in the range of 0.115 to 0.198 m3/s/m, is presented. The results show the inefficiency of circular profiles in comparison with T-shaped bars. No important influence of rack slope is found that could help to reduce clogging. This works confirms the importance of the selection of bar profile to reduce maintenance labor. A comparison of results with previous works with gravel sediment in T-shaped bars is considered. A methodology to calculate the wetted rack length considering occlusion due to flow with sediment transport is proposed, and the results are compared with those in the bibliography.

Empirical, Dimensional and Inspectional Analysis in the Design of Bottom Intake Racks

Flow over bottom racks is highly turbulent, three-dimensional and spatially varied. The design of bottom intake systems has mainly been studied in the laboratory. The comparison of existing experimental studies shows large deviations in the definition of design parameters such as wetted rack length. Each experimental study is limited to a single bar type or to a low range of void ratios, which makes it difficult to generalize the observed data. A combination of empirical, dimensional and inspectional analysis is presented as a useful tool to reduce the number of variables with influence in the design parameters, such as the wetted rack length or the mean discharge coefficient. This work includes a broad experimental campaign in which wetted rack length and mean discharge coefficient are characterized using five different bottom racks with different void ratios (area between bars divided by total area). T-shaped flat and circular bars are considered as well as five different longitudinal slopes. Empirical and inspectional analyses have allowed us to verify, in two different ways, the relation between wetted rack length and incoming flow through potential functions. The influence of the viscous forces has been studied as a function of the incoming flow. Similar results may be obtained when analysing the Froude number at the beginning of the rack, depending on the wetted rack length. A new formulation for calculating the mean discharge coefficient and wetted rack length is proposed.

Influence of Rack Slope and Approaching Conditions in Bottom Intake Systems

The study analyzes the flow over bottom racks made of longitudinal T-shaped bars. A clear water flow is considered in a laboratory flume. Free surface profiles, wetted rack lengths, and discharge coefficients are measured, changing parameters such as longitudinal slope, void ratio, and approaching flow. The present work complements existing experimental studies, considering the influence of the approaching flow conditions. The velocity field measured with Particle Image Velocimetry (PIV) technique and the pressure field with Pitot tubes are quantified. Numerical simulations (CFD) are used to complement laboratory data. The energy head along the rack is calculated and compared with the hypothesis of horizontal energy level with minimum energy at the beginning of the rack. A discharge coefficient adjustment that considers the slope, the void ratio, and the position along the rack is proposed and presented with the results of other works. Theoretical proposals to calculate the pressure field along the flow are compared with measurements in the laboratory. The relation between the static pressure head in the space of bars and the discharge coefficient is used as an alternative method to define the discharge.

A new algorithm on welding process of T-shaped plates in ship hull structure to minimize distortion based on thermal simulation

In this paper, the influence of welding sequence on the distribution of distortion on a T-shaped plate bar is investigated. The simulation consists of sequentially coupled thermal and mechanical analyses using an element birth and death technique to model the addition of welding metal to the work piece. Thermal distribution in steel T-shaped plate subjected to gas metal arc welding is determined through finite element method (FEM) in numerical simulations. Three-dimensional (3D) thermal model is simulated in ANSYS FEM commercial code. A macro code programme based on Goldak model is developed to apply thermal loading generated by the heat sources. The analyses are planned to be performed for 3D, transient and non-linear conditions. Temperature distribution during welding, welding-induced distortion fields and thermal graphs are predicted. The results are compared with the predictions from mechanical analyses. The results of four welding sequences on the magnitude of distortion in the plate are discussed and their effects on the thermal smooth distribution for special points in the plate are studied. Evaluation of the results with minimum distortion represents proper predictions and proves applicability and simplicity of the new introduced algorithm in this paper.

Assessment of a New Type I Endoleak Repair Technique Using an Anchoring Device

Type I endoleaks are one of the most frequent and life-threatening complications of thoracic endovascular aortic repair. This study aimed to assess the use of suture-anchoring devices for repairing type I endoleaks. The descending aortic aneurysm model (saccular type) was made by side-to-end anastomosis to a Dacron graft. A Matsui-Kitamura stent graft was deployed to create a proximal type I endoleak. Approximately 5 mm above the upper rim of the anastomosis, the aorta was punctured by the pistol of the suture-anchoring device with a T-shaped bar under fluoroscopy. Sutures were applied until angiography showed the absence of a type I endoleak. During the process, two pressure measurements were used to perform continuous assessments of aortic pressure and intra-aneurysm sac pressure. A mean ± SD of 5 ± 1 anchoring shots were used to eliminate type I endoleaks. The device performed well, and no complications were observed. The mean ± SD intrasac pressures before stent graft deployment, during endoleak maintenance, and after repair were 118 ± 5, 61 ± 4, and 26 ± 5 mm Hg, respectively. The postrepair pressure was significantly decreased (P < 0.001; Student t test). Despite some anatomic and clinical limitations identified during the experiments, the effectiveness of the suture-anchoring device was confirmed. Further improvement of the device will soon lead to its use as a less invasive endoleak repair procedure.

‘Succinic semialdehyde dehydrogenase deficiency: phenotype evolution in an adolescent patient at 20‐year follow‐up’

‘Succinic semialdehyde dehydrogenase deficiency: phenotype evolution in an adolescent patient at 20‐year follow‐up’

A novel six-component force sensor of good measurement isotropy and sensitivities

Abstract In this work, a novel six-component force sensor with its force-sensing member in the form of four identical T-shaped bars is presented. The force-sensing member is subjected to finite element analysis in conjunction with a design optimization for high measurement sensitivities. Although significant measurement couplings exist in this six-component force sensor, however, they distribute only in a few sparse places in the calibration matrix, making the calculations for the force components relatively easy and quick. The condition number under the full rated loading conditions for this sensor is 1.543, which represents a rather good measurement isotropy, as compared to approximately 2–4 for a Maltese crossbar sensor under similar conditions. In addition, only 20 strain gauges are required in the design, which is less than that used in a Maltese crossbar type sensor, in which at least 24 strain gauges are used.

In utero lead exposure in squirrel monkeys: motor effects seen with schedule-controlled behavior.

Timed-pregnant squirrel monkeys were exposed orally to lead during the last 1/2 to 2/3 of gestation such that maternal lead levels ranged from 21 to 70 micrograms/dl in blood. Offspring of these lead-exposed monkeys were compared to gender-matched, untreated controls (blood-lead levels from 4 to 9 micrograms/dl), born at about the same time. When the monkeys were 3 to 7 years old they were trained to pull a T-shaped bar against 1 kg spring through a displacement of 1 cm. This performance was examined during acquisition of different fixed-ratio (1, 5, and 20) and fixed-interval (120", 300", and 600") schedules of reinforcement and during steady state under the fixed-ratio 5 and fixed-interval 600". Monkeys exposed prenatally to lead showed an increased number of responses failing to meet the requirement of pulling against 1 kg spring through a 1 cm displacement when behavior was maintained by a fixed-ratio schedule, which engenders a vigorous, high-rate pattern of responding. This increased number of incomplete responses first appeared in the acquisition of a fixed-ratio 5 and fixed-ratio 20 schedules of reinforcement, remained after the fixed-ratio 5 schedule was allowed to reach steady state, and did not appear under the fixed-interval schedule. Neither body weight not response rate were affected by lead, but it was necessary to control for these variables using multiple regression to isolate lead's effect. The appearance of incomplete responses while the monkeys pulled vigorously against a 1 kg spring suggests that lead exposure during gestation produced subtle motor impairments years after exposure has ended. Deficits in the acquisition of behavior (learning) under Concurrent Random Interval schedules of reinforcement have also been reported with these monkeys. Together, these reports reveal prolonged deficits in learning and motor function resulting from in utero exposure to lead at maternal blood lead levels (21-70 micrograms/dl) that could result from exposure to ambient air in heavily polluted urban environments or in occupational settings meeting current World Health Organization standards.

Adoption of the rolling of the lightened shape of a T-shaped spring bar

Adoption of the rolling of the lightened shape of a T-shaped spring bar