Head End Research Articles

Double-angled palatal needle holder: An innovative instrument for cleft surgeries

Introduction: The devices used for cleft surgeries are different from the routine plastic surgical ones. The currently available needle holders for palatal surgeries do not address many issues like poor visibility and excessive strain for the surgeon's dominant hand. We present an innovative needle holder which could alleviate these problems. Materials and Methods: The new needle holder was inspired from the design of a Magill forceps. It was modified to a needle holder and later on the angles were adjusted for using in palatoplasty surgery. Results: The final device had following advantages: Surgeon's hands are outside the target visual field and no blind spots or shadows in the field, surgeon's wrists, elbows and shoulders were in a more comfortable position while operating from the head end. Conclusion: The double angle needle holder was really useful for oral surgeries especially palatoplasty. The position of the surgeon's hands was more comfortable; they had better visibility and was easier to maneuver.

Development and Preservation of Avian Sperm.

Terminally differentiated avian sperm consist of a head which male genetic material locates and flagellum that provides the motive force to propel them towards the fertilization site. The apical end of the sperm head accommodates a secretory vesicle, called an acrosome, that undergoes acrosome reaction releasing proteolytic content to penetrate the peri-vitelline membrane of an egg. Transcriptionally and translationally inactive, sperm need to rely on these distinct compartments in which different functions are preassembled, in order to achieve the goal of "fertilization". How are these complex structures with high functionality formed? Spermatogenesis is divided into an early stage in which diploid spermatogonia is proliferated into round spermatids thorough mitotic and meiotic divisions, and a late stage in which round spermatids are transformed into sperm though nuclear condensation and elongation of the sperm head, and formation of accessory structures. Recently, it was reported in aves that morphologically differentiated sperm undergo post-testicular maturation during passage through the male genital tract, suggesting that a similar system to mammals might be involved in the acquisition of fertilizing ability in avian sperm. Investigation for mechanisms underlying how sperm regulate their functions which are necessary to achieve fertilization is important for developing reproductive biotechnology in aves, because cryopreservation of poultry sperm is still not reliable for use in commercial production or for the preservation of genetic resources. In this review, we firstly provide an update on avian spermatogenesis, and then discuss the uniqueness of structure and functions of avian sperm, highlighting differences from mammalian sperm. Lastly, we discuss the molecular mechanism and current techniques of cryopreservation for avian sperm.

Longwall mining under gateroads and gobs of abandoned small mine

Due to the use of outdated mining technology or room and pillar mining process in small coal mines, the coal recovery ratio is only 10–25%. In many regions of China, the damage area caused by the small coal mines amounted to nearly one hundred square kilometers. Therefore, special mining techniques must be taken to reclaim the wasted resource in disturbed coal areas. This paper focuses on the different mining methods by analyzing the longwall panel layout and abandoned gateroad (AG) distribution in the abandoned area of Cuijiazhai coal mine in northwestern China. On the basis of three-dimensional geological model, FLAC3D numerical simulation was employed. The abutment pressure distribution was simulated when the panel face passed through the disturbed areas. The proper angle of the inclined face was analyzed when the panel face passed through the abandoned gateroads. The results show that the head end of the face should be 13–20m ahead of the tail end. The pillars on both sides of abandoned gateroads had not been damaged at the same time, and no large-area stress concentration occured above the main roof. Therefore, the coal reserves of disturbed areas can be successfully recovered by using underground longwall mining.

Parametric study and performance analysis of hybrid rocket motors with double-tube configuration

The practical implementation of hybrid rocket motors has historically been hampered by the slow regression rate of the solid fuel. In recent years, the research on advanced injector designs has achieved notable results in the enhancement of the regression rate and combustion efficiency of hybrid rockets. Following this path, this work studies a new configuration called double-tube characterized by injecting the gaseous oxidizer through a head end injector and an inner tube with injector holes distributed along the motor longitudinal axis. This design has demonstrated a significant potential for improving the performance of hybrid rockets by means of a better mixing of the species achieved through a customized injection of the oxidizer. Indeed, the CFD analysis of the double-tube configuration has revealed that this design may increase the regression rate over 50% with respect to the same motor with a conventional axial showerhead injector. However, in order to fully exploit the advantages of the double-tube concept, it is necessary to acquire a deeper understanding of the influence of the different design parameters in the overall performance. In this way, a parametric study is carried out taking into account the variation of the oxidizer mass flux rate, the ratio of oxidizer mass flow rate injected through the inner tube to the total oxidizer mass flow rate, and injection angle. The data for the analysis have been gathered from a large series of three-dimensional numerical simulations that considered the changes in the design parameters. The propellant combination adopted consists of gaseous oxygen as oxidizer and high-density polyethylene as solid fuel. Furthermore, the numerical model comprises Navier-Stokes equations, k-ε turbulence model, eddy-dissipation combustion model and solid-fuel pyrolysis, which is computed through user-defined functions. This numerical model was previously validated by analyzing the computational and experimental results obtained for conventional hybrid rocket designs. In addition, a performance analysis is conducted in order to evaluate the influence in the performance provoked by the possible growth of the diameter of the inner fuel grain holes during the motor operation. The latter phenomenon is known as burn through holes. Finally, after a statistical analysis of the data, a regression rate expression as a function of the design parameters is obtained.

Anti-Interference Measurement Methods of the Coupled Transmission-Line Capacitance Parameters Based on the Harmonic Components

The traditional measurement methods of capacitance parameters of coupled transmission lines bring large measurement errors under a strong electromagnetic-interference environment. To solve this problem, new anti-interference measurement methods based on harmonic components are proposed. First, the voltages and currents at the head end and the tail end of the transmission line are sampled synchronously based on global positioning system (GPS) technology, then they acquire the third harmonic components from the measured data with an interpolation fast Fourier transform algorithm, and substitute them to the calculation formulae, so that the power frequency interference signals are filtered as noise and the capacitance parameters can be accurately measured. The wiring diagram of line parameter measurement and the hardware structure of the measuring system based on GPS are given. The simulation results with PSCAD and an example of measuring two 200-kV coupled transmission lines are given. The comparison of measurement results between the proposed methods and the traditional methods is also shown.

Open wedge high tibial osteotomy using three-dimensional printed models: Experimental analysis using porcine bone

BackgroundThe purpose of this study was to evaluate the usefulness of three-dimensional (3D) printed models for open wedge high tibial osteotomy (HTO) in porcine bone. MethodsComputed tomography (CT) images were obtained from 10 porcine knees and 3D imaging was planned using the 3D-Slicer program. The osteotomy line was drawn from the three centimeters below the medial tibial plateau to the proximal end of the fibular head. Then the osteotomy gap was opened until the mechanical axis line was 62.5% from the medial border along the width of the tibial plateau, maintaining the posterior tibial slope angle. The wedge-shaped 3D-printed model was designed with the measured angle and osteotomy section and was produced by the 3D printer. The open wedge HTO surgery was reproduced in porcine bone using the 3D-printed model and the osteotomy site was fixed with a plate. Accuracy of osteotomy and posterior tibial slope was evaluated after the osteotomy. ResultsThe mean mechanical axis line on the tibial plateau was 61.8±1.5% from the medial tibia. There was no statistically significant difference (P=0.160). The planned and post-osteotomy correction wedge angles were 11.5±3.2° and 11.4±3.3°, and the posterior tibial slope angle was 11.2±2.2° pre-osteotomy and 11.4±2.5° post-osteotomy. There were no significant differences (P=0.854 and P=0.429, respectively). ConclusionThis study showed that good results could be obtained in high tibial osteotomy by using 3D printed models of porcine legs.

Erratum to: Attentional capture for tool images is driven by the head end of the tool, not the handle.

Erratum to: Attentional capture for tool images is driven by the head end of the tool, not the handle.

Numerical study of hollow rotating detonation engine with different fuel injection area ratios

Three-dimensional numerical simulations are performed to study rotating detonation engines (RDEs) with a hollow combustor. The computations are based on the reactive Euler equations. The reactions of stoichiometric hydrogen–air mixtures are calculated by the one-step Arrhenius chemistry model. The hollow RDE combustors with different fuel injection area ratios on the head end wall are considered. The fuel injection area ratios range from 55.6% to 88.9%. The number of rotating detonation waves in the flow field of the hollow combustor is found to be related to the fuel injection area ratio. In the hollow combustors with fixed dimensions, the number of detonation waves increases when the fuel injection area ratio is higher. In addition, a comparative analysis of the hollow RDE model and the conventional annular RDE model is performed with respect to the flow field and fuel injection conditions. The propulsive performance of the hollow RDE with different fuel injection area ratios is also evaluated and compared with experimental data and other simulation results. It is demonstrated from several aspects that the removal of the inner wall does not sacrifice the propulsive performance of the RDE.

The anatomy basis and clinical application of the horn fasciocutaneous perforator flaps for the reconstruction of the defects on finger soft tissue

To discuss the clinical effect of horn perforator flaps for the treatment of finger soft tissue defect. ① Lead oxide-gelatin mixture injection and CT scanning were performed in 4 fresh adult cadavers and the data was put into mimics 17.0 to achieve the three-dimensional reconstruction. The regulation and origins of the perforator vessel in proper palmar digital artery was observed. ② From July 2012 to July 2015,9 cases with finger soft tissue defects were treated with horn perforator flaps. The defect areas ranged from 0.6 cm × 0.8 cm to 1.2 cm × 1.5 cm and the flap size ranged from0.8 cm×2.5 cm to 1.6 cm×4.2 cm. We put the head end of flaps at defect side. The horn perforator flap was designed with 1-2 perforator vessel and rotated to cover the defect. The defect at donor site was closed directly. We got 4 symmetric arteries in palmar and back surfaces of fingers,2 for proper palmar digital arteries and 2 for dorsal digital arteries. The proper palmar digital arteries have a larger diameter which is the main source of blood supply for fingers. All 9 flaps survived after the operation. Both the recipient area and donor areas received sound healing. With 2 months to 1.5 years of follow-up visit, the shape, color and luster, texture and function all had good healing. The horn perforator flaps for repair finger soft tissue defect have advantages of flexible design, reliable perforator vessels. The defect at donor site can be closed directly with no skin graft. This method considers both shape and function and is a good way for finger soft tissue defect.

A simplified computational fluid-dynamic approach to the oxidizer injector design in hybrid rockets

Fuel regression rate in hybrid rockets is non-negligibly affected by the oxidizer injection pattern. In this paper a simplified computational approach developed in an attempt to optimize the oxidizer injector design is discussed. Numerical simulations of the thermo-fluid-dynamic field in a hybrid rocket are carried out, with a commercial solver, to investigate into several injection configurations with the aim of increasing the fuel regression rate and minimizing the consumption unevenness, but still favoring the establishment of flow recirculation at the motor head end, which is generated with an axial nozzle injector and has been demonstrated to promote combustion stability, and both larger efficiency and regression rate. All the computations have been performed on the configuration of a lab-scale hybrid rocket motor available at the propulsion laboratory of the University of Naples with typical operating conditions.After a preliminary comparison between the two baseline limiting cases of an axial subsonic nozzle injector and a uniform injection through the prechamber, a parametric analysis has been carried out by varying the oxidizer jet flow divergence angle, as well as the grain port diameter and the oxidizer mass flux to study the effect of the flow divergence on heat transfer distribution over the fuel surface. Some experimental firing test data are presented, and, under the hypothesis that fuel regression rate and surface heat flux are proportional, the measured fuel consumption axial profiles are compared with the predicted surface heat flux showing fairly good agreement, which allowed validating the employed design approach. Finally an optimized injector design is proposed.

Evaluation of Physical and Durability Characteristics of New Headed Glass Fiber–Reinforced Polymer Bars for Concrete Structures

This paper presents the results of a collaborative research project between Quebec’s Ministry of Transportation and Ontario’s Ministry of Transportation, which aimed at characterizing a new type of headed glass fiber–reinforced polymer (GFRP) reinforcing bar and evaluating its suitability as internal reinforcement for concrete structures. To achieve these objectives, the project was implemented in three stages: (1) evaluation of the physical and mechanical properties; (2) determination of the pullout behavior in concrete; and (3) characterization of the long-term durability of the headed GFRP bars. A total of 57 specimens embedded in a 200-mm concrete cube were tested with the direct pullout test to investigate the effect of confinement, bar size, concrete compressive strength, and exposure conditions on the pullout behavior of the headed GFRP bars. Simultaneously, microstructural analyses and measurements of the physicochemical and mechanical properties were carried out on conditioned and unconditioned headed GFRP bars. The results show that the materials, geometry, and interface configuration of the head provided very good mechanical interlocking to the GFRP bars. Up to 63 and 53% of the guaranteed tensile strength of the straight GFRP bars were achieved for 15.9- and 19-mm diameter bars with headed ends, respectively. Scanning electron microscopy and differential scanning calorimetry showed no material changes in the head and bars after exposure to alkaline solution and freeze–thaw cycling. Exposure to the alkaline solution under sustained loading had the most detrimental effect, with the bar retaining 79.4% of its pullout strength. The results indicate that the tested headed GFRP bar has suitable mechanical and durability properties for use as reinforcement in concrete bridge components.

Attentional capture for tool images is driven by the head end of the tool, not the handle.

Tools afford specialized actions that are tied closely to object identity. Although there is mounting evidence that functional objects, such as tools, capture visuospatial attention relative to non-tool competitors, this leaves open the question of which part of a tool drives attentional capture. We used a modified version of the Posner cueing task to determine whether attention is oriented towards the head versus the handle of realistic images of common elongated tools. We compared cueing effects for tools with control stimuli that consisted of images of fruit and vegetables of comparable elongation to the tools. Critically, our displays controlled for lower-level influences on attention that can arise from global shape asymmetries in the image cues. Observers were faster to detect low-contrast targets positioned near the head end versus the handle of tools. As expected, no lateralized performance bias was observed for the control stimuli. In a follow-up experiment, we confirmed that the bias towards tool heads was not due to inhibition of return as a result of early attentional orienting towards tool handles. Finally, we confirmed that real-world exemplars of the tools in the cueing studies were associated more strongly with specific grasping patterns than the elongated fruits and vegetables. Together, our results demonstrate that affordance effects on attentional capture are driven by the head end of a tool. Prioritizing the head end of a tool is adaptive because it ensures that the most relevant region of the object takes priority in selecting an effective motor plan.

PROFITABILITY OF CROP PRODUCTION UNDER THE KANO RIVER IRRIGATION PROJECT, NORTHERN, NIGERIA

Four major crops rice, maize, wheat and tomato were examined in the Kano River Irrigation Project. The project was divided into 3 sections; the head, middle and tail ends. One hundred farmers were randomly selected from each sections making a total of 300 hundred farmers. Net farm income, and profitability index were used to assess the profitability of the enterprises. It was concluded Rice, maize, and wheat were profitable while tomato was unprofitable that year attributable to market glut and perishability of the crop. It was recommended that storage facilities be provided by both private and government agencies to curtail the losses incurred by the farmers.

Unilateral visual loss due to central retinal artery occlusion with total ophthalmoplegia following cervical spine surgery in prone position.

Blindness after spinal surgery is a rare complication, but it is serious, irreversible and incurable. Central retinal artery occlusion (CRAO) is rare after spinal surgery and ophthalmoplegia is even rarer. A 52-year-old male patient complained of loss of vision in right eye immediately after cervical spine surgery. On examination, the patient's visual acuity in right eye was absent perception of light. Right eye pupil was dialated and relative afferent pupillary defect (RAPD) was present. Extraocular movements were absent in all gazes in right eye. Intra-ocular pressure (IOP) was 26 mmHg in right eye and 16 mmHg in the left. Posterior segment examination revealed blurred disc margin with ischemic whitening of retina, thin and attenuated retinal arterioles and a central cherry red spot in right eye. Left eye was essentially normal. The causal factors of blindness in the patient were likely ischemia of the retina after venous congestion or temporary arterial occlusion resulting from changes in pressure to the tissues of the orbit. Factors including prolonged prone positioning with head end dependent position and possibility of orbital compression by the headrest could have contributed to impaired venous drainage, increase in IOP and reduction in perfusion pressure. Loss of vision post spinal surgery is a rarest of complication yet grave and irreversible. Because the problem involves mainly prone positioning of the patient, an appropriate position should be found so that facial and ocular compression can be avoided.

Comprehensive structural characterization of polyisoprene synthesized via cationic mechanism

The microstructure of polyisoprene synthesized with tBuCl/TiCl4 initiating system is investigated using 1D and 2D (HSQC and HMBC) NMR spectroscopy. It is found that trans-1,4-units with regular (head-to-tail) and inverse (tail-to-tail) and (head-to-head) enchainments are predominant structures of unsaturated part of polymer chain, while 1,2- and 3,4-units are presented in minor amounts. The new methodology for the quantitative calculation of the content of different structural units in polyisoprene chain including both types of inverse trans-1,4-addition (tail-to-tail and head-to-head) is proposed. It is shown that head groups consist of tert-butyl group connected to trans-1,4-unit of polyisoprene chain. In addition, two types of chlorine-containing end groups are found (trans-4,1-Cl and 4,3-Cl), while conjugated double bonds at the chain end are totally absent. The methodology for the calculation of number-average functionality by tert-butyl head and chlorine end groups, respectively, is developed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2430–2442

A methodology to estimate equity of canal water and groundwater use at different spatial and temporal scales: a geo-informatics approach

Indus basin irrigation system (IBIS) is one of the largest contiguous irrigation systems of the world. The surface canal water supplies are far less than the crop water demands which lead farmers to use groundwater to cope surface water scarcity. Although many studies in the IBIS are conducted to analyze the equitable distribution of canal water, there is hardly any study which comprehensively analyze the equitable use of canal water and groundwater at different spatial and temporal scales. One of the main reasons is lack of reliable information on the volume of groundwater abstraction. The objective of the current study is to develop an approach for estimating the equity of canal water and groundwater use at different spatial (canal command, distributaries, head, middle and tail end reaches) and temporal (daily, monthly and seasonal) scales of Hakra canal command area of IBIS. Results show that canal water and groundwater use to meet actual evapotranspiration is 34 and 42 %, respectively, which makes groundwater as an integral part of the large canal irrigation schemes of IBIS. The canal water and groundwater use varies significantly during the cropping colander. The maximum groundwater use is during May (51 mm) whereas the maximum canal water use is during August (24 mm). Farmers located at the head end reaches of Hakra canal use 42 % groundwater of total groundwater use whereas farmers located at the middle and tail end reaches use only 35 and 23 %, respectively. The canal water use at the head, middle and tail end reaches is 40, 34 and 26 %, respectively. These results show that the farmers located at the head of Hakra canal command area use more canal water and groundwater as compared to those located at the middle and tail end reaches. This methodology can provide guidelines to water managers in the region for equitable use of both canal water and groundwater.

Hybrid Rockets with Axial Injector: Port Diameter Effect on Fuel Regression Rate

A numerical rebuilding of a series of test data obtained with static firings of a lab-scale hybrid rocket is carried out with a Reynolds-averaged Navier–Stokes solver including detailed gas–surface interaction modeling based on surface mass and energy balances. Two experimental campaigns are considered in which gaseous oxygen is fed into axisymmetric hydroxyl-terminated polybutadiene grains through an axial conical subsonic nozzle. A validation rebuilding of all of the firing tests has been performed first to highlight numerical prediction capabilities and modeling limits. Despite the several geometrical simplifications, which allows using a reduced number of cells in the computational domain and thus performing parametric analyses efficiently, the present computational fluid dynamics approach is able to capture the main features of the motor internal ballistics, fairly reproducing the average chamber pressure values and the fuel regression rate trends with oxidizer mass flux and port diameter. Computed flowfields show the establishment of a recirculation region at the motor head end, with a variable extension depending on the port diameter, which promotes propellant mixing and raises the fuel regression rate. Numerical simulations, supported by the experimental results, clarify the mechanism through which the port diameter has a direct influence on the fuel regression.

Studies on EVA‐Based Wax Fuel for Launch Vehicle Applications

AbstractA fuel for the hybrid rocket system was developed. The attempts made to improve the mechanical properties of wax by adding EVA (ethylene vinyl acetate) are illustrated. It was observed that the mechanical properties obtained by adding EVA to wax were dependent on the process of curing the fuel specimen. A proprietary method of curing the fuel specimen was established. The percentage elongation obtained with 20 % EVA and 80 % of wax was around 17 %, which was much higher than the values obtained with pure wax (4 %). It was observed from the study that the higher the percentage of EVA content in wax was, the better the mechanical properties were. Regression rate studies with EVA and wax combination were carried out. It was observed that the regression rate decreased upon addition of EVA in wax. This reduction was compensated by using a bluff body at the head end. The regression rate obtained with 20 % EVA and 80 % wax even with the use of bluff body is lower than that obtained with pure wax, but is around 3.5 times the regression rate obtained with polymeric fuels.

Effect of Shear Studs and High Moments on Punching Behavior of GFRP-RC Slab–Column Edge Connections

AbstractThis paper presents test results of six full-scale glass fiber-reinforced polymer (GFRP) reinforced concrete slab–column edge connections. The test connections included two series with three connections each. The connections of Series 1 investigated the effect of a new type of GFRP shear reinforcement on the punching shear behavior of slab-column edge connections, while those of Series 2 investigated the effect of moment-to-shear ratio. For Series 1, one connection did not have shear reinforcement, while the other two connections had ribbed-deformed GFRP shear studs with headed ends at different radial spacing (120 and 80 mm). For Series 2, three different moment-to-shear ratios were applied to the connections (0.2, 0.4, and 0.6 m). The typical dimensions of the slabs were 2,800×1,550×200 mm with a 300-mm square column extending above and below the slab. The headed ends of the studs provided adequate anchorage, which allowed the studs to control the propagation of shear cracks and to increase the...

Calculation of the joint strength of hot shear joined bars based on a modified lemaitre model

To join the head and tail ends of two steel bars together, a solid-state joining technology named “shear joining” has been developed. In the process, no external heating is required since the bar temperature is around 1000 °C and sufficiently high for joining. Compared with the laser welding and fusion welding, the head and tail ends are joined together within a short time by pressing and shearing. So the process is very easy, quick and reliable without special heating and forming processes. As an innovative process, there is no appropriate method to evaluate the strength of joint up to now. In this research, a modified Lemaitre model was put forward to predict the strength of joint. This model could be also used to improve the design of joining tools and process conditions. Through comparison of load-displacement curves of tensile test obtained from FE simulation and experiment, the reliability of numerical model was verified. Compared with experimental results, the predicted joint strength showed a good quantitative agreement.